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When testing overflow and overread, there is no need to keep unnecessary
compilation warnings, we should simply ignore them.
The motivation for this patch is to eliminate the compilation warning,
maybe one day we will compile the kernel with "-Werror -Wall", at which
point this compilation warning will turn into a compilation error, we
should fix this error in advance.
How to reproduce the problem (with gcc-11.3.1):
$ make -C tools/testing/selftests/
...
warning: `write' reading 4294967295 bytes from a region of size 1
[-Wstringop-overread]
warning: `read' writing 4294967295 bytes into a region of size 25
overflows the destination [-Wstringop-overflow=]
"-Wno-stringop-overread" is supported at least in gcc-11.1.0.
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=d14c547abd484d3540b692bb8048c4a6efe92c8b
Link: https://lkml.kernel.org/r/tencent_51C4ACA8CB3895C2D7F35178440283602107@qq.com
Signed-off-by: Rong Tao <rongtao@cestc.cn>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The ei pointer does not need to cast the type.
Link: https://lkml.kernel.org/r/20221107015659.3221-1-zeming@nfschina.com
Signed-off-by: Li zeming <zeming@nfschina.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently, drop_caches are reclaiming node-by-node, looping on each node
until reclaim could not make progress. This can however leave quite some
slab entries (such as filesystem inodes) unreclaimed if objects say on
node 1 keep objects on node 0 pinned. So move the "loop until no
progress" loop to the node-by-node iteration to retry reclaim also on
other nodes if reclaim on some nodes made progress. This fixes problem
when drop_caches was not reclaiming lots of otherwise perfectly fine to
reclaim inodes.
Link: https://lkml.kernel.org/r/20221115123255.12559-1-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: You Zhou <you.zhou@intel.com>
Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Tested-by: Pengfei Xu <pengfei.xu@intel.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Since commit 9a10064f56 ("mm: add a field to store names for private
anonymous memory"), name for private anonymous memory, but not shared
anonymous, can be set. However, naming shared anonymous memory just as
useful for tracking purposes.
Extend the functionality to be able to set names for shared anon.
There are two ways to create anonymous shared memory, using memfd or
directly via mmap():
1. fd = memfd_create(...)
mem = mmap(..., MAP_SHARED, fd, ...)
2. mem = mmap(..., MAP_SHARED | MAP_ANONYMOUS, -1, ...)
In both cases the anonymous shared memory is created the same way by
mapping an unlinked file on tmpfs.
The memfd way allows to give a name for anonymous shared memory, but
not useful when parts of shared memory require to have distinct names.
Example use case: The VMM maps VM memory as anonymous shared memory (not
private because VMM is sandboxed and drivers are running in their own
processes). However, the VM tells back to the VMM how parts of the memory
are actually used by the guest, how each of the segments should be backed
(i.e. 4K pages, 2M pages), and some other information about the segments.
The naming allows us to monitor the effective memory footprint for each
of these segments from the host without looking inside the guest.
Sample output:
/* Create shared anonymous segmenet */
anon_shmem = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS, -1, 0);
/* Name the segment: "MY-NAME" */
rv = prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME,
anon_shmem, SIZE, "MY-NAME");
cat /proc/<pid>/maps (and smaps):
7fc8e2b4c000-7fc8f2b4c000 rw-s 00000000 00:01 1024 [anon_shmem:MY-NAME]
If the segment is not named, the output is:
7fc8e2b4c000-7fc8f2b4c000 rw-s 00000000 00:01 1024 /dev/zero (deleted)
Link: https://lkml.kernel.org/r/20221115020602.804224-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Colin Cross <ccross@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: xu xin <cgel.zte@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The shrinker.h header depends on a user including other headers before it
for types used by shrinker.h. Fix this by including the appropriate
headers in shrinker.h.
./include/linux/shrinker.h:13:9: error: unknown type name `gfp_t'
13 | gfp_t gfp_mask;
| ^~~~~
./include/linux/shrinker.h:71:26: error: field `list' has incomplete type
71 | struct list_head list;
| ^~~~
./include/linux/shrinker.h:82:9: error: unknown type name `atomic_long_t'
82 | atomic_long_t *nr_deferred;
|
Link: https://lkml.kernel.org/r/20221114235949.201749-1-tjmercier@google.com
Fixes: 83aeeada7c ("vmscan: use atomic-long for shrinker batching")
Fixes: b0d40c92ad ("superblock: introduce per-sb cache shrinker infrastructure")
Signed-off-by: T.J. Mercier <tjmercier@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The common hugetlb unmap routine __unmap_hugepage_range performs mmu
notification calls. However, in the case where __unmap_hugepage_range is
called via __unmap_hugepage_range_final, mmu notification calls are
performed earlier in other calling routines.
Remove mmu notification calls from __unmap_hugepage_range. Add
notification calls to the only other caller: unmap_hugepage_range.
unmap_hugepage_range is called for truncation and hole punch, so change
notification type from UNMAP to CLEAR as this is more appropriate.
Link: https://lkml.kernel.org/r/20221114235507.294320-4-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Suggested-by: Peter Xu <peterx@redhat.com>
Cc: Wei Chen <harperchen1110@gmail.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's add one sanity check for CONFIG_DEBUG_VM on the write bit in
whatever chance we have when walking through the pgtables. It can bring
the error earlier even before the app notices the data was corrupted on
the snapshot. Also it helps us to identify this is a wrong pgtable setup,
so hopefully a great information to have for debugging too.
Link: https://lkml.kernel.org/r/20221114000447.1681003-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
MADV_FREE pages have been moved into the LRU_INACTIVE_FILE list by commit
f7ad2a6cb9 ("mm: move MADV_FREE pages into LRU_INACTIVE_FILE list").
Link: https://lkml.kernel.org/r/20221111034639.3593380-1-wenjian1@xiaomi.com
Signed-off-by: Jian Wen <wenjian1@xiaomi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
alloc_memory_type() returns error pointers on error instead of NULL. Use
IS_ERR() to check the return value to fix this.
Link: https://lkml.kernel.org/r/20221110030751.1627266-1-linmq006@gmail.com
Fixes: 7b88bda376 ("mm/demotion/dax/kmem: set node's abstract distance to MEMTIER_DEFAULT_DAX_ADISTANCE")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Wei Xu <weixugc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Quite straightforward, the page functions are converted to corresponding
folio functions. Same for comments.
THP specific code are converted to be large folio.
Link: https://lkml.kernel.org/r/20221109012348.93849-3-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "migrate: convert migrate_pages()/unmap_and_move() to use
folios", v2.
The conversion is quite straightforward, just replace the page API to the
corresponding folio API. migrate_pages() and unmap_and_move() mostly work
with folios (head pages) only.
This patch (of 2):
Quite straightforward, the page functions are converted to corresponding
folio functions. Same for comments.
Link: https://lkml.kernel.org/r/20221109012348.93849-1-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20221109012348.93849-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Revert commit 8315682148 ("mm: migration: fix the FOLL_GET failure on
following huge page"), since after commit 1a6baaa0db ("s390/hugetlb:
switch to generic version of follow_huge_pud()") and commit 57a196a584
("hugetlb: simplify hugetlb handling in follow_page_mask") were merged,
now all the following huge page routines can support FOLL_GET operation.
Link: https://lkml.kernel.org/r/496786039852aba90ffa68f10d0df3f4236a990b.1667983080.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Haiyue Wang <haiyue.wang@intel.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
commit fdf756f712 ("sched: Fix more TASK_state comparisons") makes
hung_task not to monitor TASK_IDLE tasks. The special handling to
workaround hung_task warnings is not required anymore.
Link: https://lkml.kernel.org/r/1667986006-25420-1-git-send-email-quic_pkondeti@quicinc.com
Signed-off-by: Pavankumar Kondeti <quic_pkondeti@quicinc.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add a new flag to zram block state that shows if the page is
incompressible: that none of the algorithm (including secondary ones)
could compress it.
Link: https://lkml.kernel.org/r/20221109115047.2921851-14-senozhatsky@chromium.org
Suggested-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Recompression iterates through all the registered secondary compression
algorithms in order of their priorities so that we have higher chances of
finding the algorithm that compresses a particular page. This, however,
may not always be best approach and sometimes we may want to limit
recompression to only one particular algorithm. For instance, when a
higher priority algorithm uses too much power and device has a relatively
low battery level we may want to limit recompression to use only a lower
priority algorithm, which uses less power.
Introduce algo= parameter support to recompression sysfs knob so that
user-sapce can request recompression with particular algorithm only:
echo "type=idle algo=zstd" > /sys/block/zramX/recompress
Link: https://lkml.kernel.org/r/20221109115047.2921851-11-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
It makes no sense for us to recompress the object if it will be in the
same size class. We anyway don't get any memory gain. But, at the same
time, we get a CPU time overhead when inserting this object into zspage
and decompressing it afterwards.
[senozhatsky: rebased and fixed conflicts]
Link: https://lkml.kernel.org/r/20221109115047.2921851-9-senozhatsky@chromium.org
Signed-off-by: Alexey Romanov <avromanov@sberdevices.ru>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add a new flag to zram block state that shows if the page was recompressed
(using alternative compression algorithm).
Link: https://lkml.kernel.org/r/20221109115047.2921851-6-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Allow zram to recompress (using secondary compression streams)
pages.
Re-compression algorithms (we support up to 3 at this stage)
are selected via recomp_algorithm:
echo "algo=zstd priority=1" > /sys/block/zramX/recomp_algorithm
Please read documentation for more details.
We support several recompression modes:
1) IDLE pages recompression is activated by `idle` mode
echo "type=idle" > /sys/block/zram0/recompress
2) Since there may be many idle pages user-space may pass a size
threshold value (in bytes) and we will recompress pages only
of equal or greater size:
echo "threshold=888" > /sys/block/zram0/recompress
3) HUGE pages recompression is activated by `huge` mode
echo "type=huge" > /sys/block/zram0/recompress
4) HUGE_IDLE pages recompression is activated by `huge_idle` mode
echo "type=huge_idle" > /sys/block/zram0/recompress
[senozhatsky@chromium.org: we should always zero out err variable in recompress loop[
Link: https://lkml.kernel.org/r/20221110143423.3250790-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20221109115047.2921851-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Introduce recomp_algorithm sysfs knob that controls secondary algorithm
selection used for recompression.
We will support up to 3 secondary compression algorithms which are sorted
in order of their priority. To select an algorithm user has to provide
its name and priority:
echo "algo=zstd priority=1" > /sys/block/zramX/recomp_algorithm
echo "algo=deflate priority=2" > /sys/block/zramX/recomp_algorithm
During recompression zram iterates through the list of registered
secondary algorithms in order of their priorities.
We also have a short version for cases when there is only
one secondary compression algorithm:
echo "algo=zstd" > /sys/block/zramX/recomp_algorithm
This will register zstd as the secondary algorithm with priority 1.
Link: https://lkml.kernel.org/r/20221109115047.2921851-3-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "zram: Support multiple compression streams", v5.
This series adds support for multiple compression streams. The main idea
is that different compression algorithms have different characteristics
and zram may benefit when it uses a combination of algorithms: a default
algorithm that is faster but have lower compression rate and a secondary
algorithm that can use higher compression rate at a price of slower
compression/decompression.
There are several use-case for this functionality:
- huge pages re-compression: zstd or deflate can successfully compress
huge pages (~50% of huge pages on my synthetic ChromeOS tests), IOW
pages that lzo was not able to compress.
- idle pages re-compression: idle/cold pages sit in the memory and we
may reduce zsmalloc memory usage if we recompress those idle pages.
Userspace has a number of ways to control the behavior and impact of zram
recompression: what type of pages should be recompressed, size watermarks,
etc. Please refer to documentation patch.
This patch (of 13):
The patch turns compression streams and compressor algorithm name struct
zram members into arrays, so that we can have multiple compression streams
support (in the next patches).
The patch uses a rather explicit API for compressor selection:
- Get primary (default) compression stream
zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP])
- Get secondary compression stream
zcomp_stream_get(zram->comps[ZRAM_SECONDARY_COMP])
We use similar API for compression streams put().
At this point we always have just one compression stream,
since CONFIG_ZRAM_MULTI_COMP is not yet defined.
Link: https://lkml.kernel.org/r/20221109115047.2921851-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20221109115047.2921851-2-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Flag delayed_rmap of 'struct mmu_gather' is rather a private member, but
it is still accessed directly. Instead, let the TLB gather code access
the flag.
Link: https://lkml.kernel.org/r/Y3SWCu6NRaMQ5dbD@li-4a3a4a4c-28e5-11b2-a85c-a8d192c6f089.ibm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When we remove a page table entry, we are very careful to only free the
page after we have flushed the TLB, because other CPUs could still be
using the page through stale TLB entries until after the flush.
However, we have removed the rmap entry for that page early, which means
that functions like folio_mkclean() would end up not serializing with the
page table lock because the page had already been made invisible to rmap.
And that is a problem, because while the TLB entry exists, we could end up
with the following situation:
(a) one CPU could come in and clean it, never seeing our mapping of the
page
(b) another CPU could continue to use the stale and dirty TLB entry and
continue to write to said page
resulting in a page that has been dirtied, but then marked clean again,
all while another CPU might have dirtied it some more.
End result: possibly lost dirty data.
This extends our current TLB gather infrastructure to optionally track a
"should I do a delayed page_remove_rmap() for this page after flushing the
TLB". It uses the newly introduced 'encoded page pointer' to do that
without having to keep separate data around.
Note, this is complicated by a couple of issues:
- we want to delay the rmap removal, but not past the page table lock,
because that simplifies the memcg accounting
- only SMP configurations want to delay TLB flushing, since on UP
there are obviously no remote TLBs to worry about, and the page
table lock means there are no preemption issues either
- s390 has its own mmu_gather model that doesn't delay TLB flushing,
and as a result also does not want the delayed rmap. As such, we can
treat S390 like the UP case and use a common fallback for the "no
delays" case.
- we can track an enormous number of pages in our mmu_gather structure,
with MAX_GATHER_BATCH_COUNT batches of MAX_TABLE_BATCH pages each,
all set up to be approximately 10k pending pages.
We do not want to have a huge number of batched pages that we then
need to check for delayed rmap handling inside the page table lock.
Particularly that last point results in a noteworthy detail, where the
normal page batch gathering is limited once we have delayed rmaps pending,
in such a way that only the last batch (the so-called "active batch") in
the mmu_gather structure can have any delayed entries.
NOTE! While the "possibly lost dirty data" sounds catastrophic, for this
all to happen you need to have a user thread doing either madvise() with
MADV_DONTNEED or a full re-mmap() of the area concurrently with another
thread continuing to use said mapping.
So arguably this is about user space doing crazy things, but from a VM
consistency standpoint it's better if we track the dirty bit properly even
when user space goes off the rails.
[akpm@linux-foundation.org: fix UP build, per Linus]
Link: https://lore.kernel.org/all/B88D3073-440A-41C7-95F4-895D3F657EF2@gmail.com/
Link: https://lkml.kernel.org/r/20221109203051.1835763-4-torvalds@linux-foundation.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hugh Dickins <hughd@google.com>
Reported-by: Nadav Amit <nadav.amit@gmail.com>
Tested-by: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This is purely a preparatory patch that makes all the data structures
ready for encoding flags with the mmu_gather page pointers.
The code currently always sets the flag to zero and doesn't use it yet,
but now it's tracking the type state along. The next step will be to
actually start using it.
Link: https://lkml.kernel.org/r/20221109203051.1835763-3-torvalds@linux-foundation.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
release_pages() already could take either an array of page pointers, or an
array of folio pointers. Expand it to also accept an array of encoded
page pointers, which is what both the existing mlock() use and the
upcoming mmu_gather use of encoded page pointers wants.
Note that release_pages() won't actually use, or react to, any extra
encoded bits. Instead, this is very much a case of "I have walked the
array of encoded pages and done everything the extra bits tell me to do,
now release it all".
Also, while the "either page or folio pointers" dual use was handled with
a cast of the pointer in "release_folios()", this takes a slightly
different approach and uses the "transparent union" attribute to describe
the set of arguments to the function:
https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html
which has been supported by gcc forever, but the kernel hasn't used
before.
That allows us to avoid using various wrappers with casts, and just use
the same function regardless of use.
Link: https://lkml.kernel.org/r/20221109203051.1835763-2-torvalds@linux-foundation.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We already have this notion in parts of the MM code (see the mlock code
with the LRU_PAGE and NEW_PAGE bits), but I'm going to introduce a new
case, and I refuse to do the same thing we've done before where we just
put bits in the raw pointer and say it's still a normal pointer.
So this introduces a 'struct encoded_page' pointer that cannot be used for
anything else than to encode a real page pointer and a couple of extra
bits in the low bits. That way the compiler can trivially track the state
of the pointer and you just explicitly encode and decode the extra bits.
Note that this makes the alignment of 'struct page' explicit even for the
case where CONFIG_HAVE_ALIGNED_STRUCT_PAGE is not set. That is entirely
redundant in almost all cases, since the page structure already contains
several word-sized entries.
However, on m68k, the alignment of even 32-bit data is just 16 bits, and
as such in theory the alignment of 'struct page' could be too. So let's
just make it very very explicit that the alignment needs to be at least 32
bits, giving us a guarantee of two unused low bits in the pointer.
Now, in practice, our page struct array is aligned much more than that
anyway, even on m68k, and our existing code in mm/mlock.c obviously
already depended on that. But since the whole point of this change is to
be careful about the type system when hiding extra bits in the pointer,
let's also be explicit about the assumptions we make.
NOTE! This is being very careful in another way too: it has a build-time
assertion that the 'flags' added to the page pointer actually fit in the
two bits. That means that this helper must be inlined, and can only be
used in contexts where the compiler can statically determine that the
value fits in the available bits.
[akpm@linux-foundation.org: kerneldoc on a forward-declared struct confuses htmldocs]
Link: https://lore.kernel.org/all/Y2tKixpO4RO6DgW5@tuxmaker.boeblingen.de.ibm.com/
Link: https://lkml.kernel.org/r/20221109203051.1835763-1-torvalds@linux-foundation.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hugh Dickins <hughd@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com> [s390]
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's extend the test to cover the possible mprotect() optimization when
removing write-protection. mprotect() must not allow write-access to a
COW-shared page by accident.
Link: https://lkml.kernel.org/r/20221108174652.198904-8-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
NUMA hinting no longer uses savedwrite, let's rip it out.
... and while at it, drop __pte_write() and __pmd_write() on ppc64.
Link: https://lkml.kernel.org/r/20221108174652.198904-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
commit b191f9b106 ("mm: numa: preserve PTE write permissions across a
NUMA hinting fault") added remembering write permissions using ordinary
pte_write() for PROT_NONE mapped pages to avoid write faults when
remapping the page !PROT_NONE on NUMA hinting faults.
That commit noted:
The patch looks hacky but the alternatives looked worse. The tidest was
to rewalk the page tables after a hinting fault but it was more complex
than this approach and the performance was worse. It's not generally
safe to just mark the page writable during the fault if it's a write
fault as it may have been read-only for COW so that approach was
discarded.
Later, commit 288bc54949 ("mm/autonuma: let architecture override how
the write bit should be stashed in a protnone pte.") introduced a family
of savedwrite PTE functions that didn't necessarily improve the whole
situation.
One confusing thing is that nowadays, if a page is pte_protnone()
and pte_savedwrite() then also pte_write() is true. Another source of
confusion is that there is only a single pte_mk_savedwrite() call in the
kernel. All other write-protection code seems to silently rely on
pte_wrprotect().
Ever since PageAnonExclusive was introduced and we started using it in
mprotect context via commit 64fe24a3e0 ("mm/mprotect: try avoiding write
faults for exclusive anonymous pages when changing protection"), we do
have machinery in place to avoid write faults when changing protection,
which is exactly what we want to do here.
Let's similarly do what ordinary mprotect() does nowadays when upgrading
write permissions and reuse can_change_pte_writable() and
can_change_pmd_writable() to detect if we can upgrade PTE permissions to be
writable.
For anonymous pages there should be absolutely no change: if an
anonymous page is not exclusive, it could not have been mapped writable --
because only exclusive anonymous pages can be mapped writable.
However, there *might* be a change for writable shared mappings that
require writenotify: if they are not dirty, we cannot map them writable.
While it might not matter in practice, we'd need a different way to
identify whether writenotify is actually required -- and ordinary mprotect
would benefit from that as well.
Note that we don't optimize for the actual migration case:
(1) When migration succeeds the new PTE will not be writable because the
source PTE was not writable (protnone); in the future we
might just optimize that case similarly by reusing
can_change_pte_writable()/can_change_pmd_writable() when removing
migration PTEs.
(2) When migration fails, we'd have to recalculate the "writable" flag
because we temporarily dropped the PT lock; for now keep it simple and
set "writable=false".
We'll remove all savedwrite leftovers next.
Link: https://lkml.kernel.org/r/20221108174652.198904-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's factor the check out into vma_wants_manual_pte_write_upgrade(), to be
reused in NUMA hinting fault context soon.
Link: https://lkml.kernel.org/r/20221108174652.198904-5-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's replicate what we have for PTEs in can_change_pte_writable() also
for PMDs.
While this might look like a pure performance improvement, we'll us this to
get rid of savedwrite handling in do_huge_pmd_numa_page() next. Place
do_huge_pmd_numa_page() strategically good for that purpose.
Note that MM_CP_TRY_CHANGE_WRITABLE is currently only set when we come
via mprotect_fixup().
Link: https://lkml.kernel.org/r/20221108174652.198904-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We want to replicate this code for handling PMDs soon.
(1) No need to crash the kernel, warning and rejecting is good enough. As
this will no longer get optimized out, drop the pte_write() check: no
harm would be done.
(2) Add a comment why PROT_NONE mapped pages are excluded.
(3) Add a comment regarding MAP_SHARED handling and why we rely on the
dirty bit in the PTE.
Link: https://lkml.kernel.org/r/20221108174652.198904-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/autonuma: replace savedwrite infrastructure", v2.
As discussed in my talk at LPC, we can reuse the same mechanism for
deciding whether to map a pte writable when upgrading permissions via
mprotect() -- e.g., PROT_READ -> PROT_READ|PROT_WRITE -- to replace the
savedwrite infrastructure used for NUMA hinting faults (e.g., PROT_NONE ->
PROT_READ|PROT_WRITE).
Instead of maintaining previous write permissions for a pte/pmd, we
re-determine if the pte/pmd can be writable. The big benefit is that we
have a common logic for deciding whether we can map a pte/pmd writable on
protection changes.
For private mappings, there should be no difference -- from what I
understand, that is what autonuma benchmarks care about.
I ran autonumabench for v1 on a system with 2 NUMA nodes, 96 GiB each via:
perf stat --null --repeat 10
The numa01 benchmark is quite noisy in my environment and I failed to
reduce the noise so far.
numa01:
mm-unstable: 146.88 +- 6.54 seconds time elapsed ( +- 4.45% )
mm-unstable++: 147.45 +- 13.39 seconds time elapsed ( +- 9.08% )
numa02:
mm-unstable: 16.0300 +- 0.0624 seconds time elapsed ( +- 0.39% )
mm-unstable++: 16.1281 +- 0.0945 seconds time elapsed ( +- 0.59% )
It is worth noting that for shared writable mappings that require
writenotify, we will only avoid write faults if the pte/pmd is dirty
(inherited from the older mprotect logic). If we ever care about
optimizing that further, we'd need a different mechanism to identify
whether the FS still needs to get notified on the next write access.
In any case, such an optimization will then not be autonuma-specific, but
mprotect() permission upgrades would similarly benefit from it.
This patch (of 7):
Anonymous pages might have the dirty bit clear, but this should not
prevent mprotect from making them writable if they are exclusive.
Therefore, skip the test whether the page is dirty in this case.
Note that there are already other ways to get a writable PTE mapping an
anonymous page that is clean: for example, via MADV_FREE. In an ideal
world, we'd have a different indication from the FS whether writenotify is
still required.
[david@redhat.com: return directly; update description]
Link: https://lkml.kernel.org/r/20221108174652.198904-1-david@redhat.com
Link: https://lkml.kernel.org/r/20221108174652.198904-2-david@redhat.com
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
It's hard to add a page_add_anon_rmap() into __split_huge_pmd_locked()'s
HPAGE_PMD_NR set_pte_at() loop, without wincing at the "freeze" case's
HPAGE_PMD_NR page_remove_rmap() loop below it.
It's just a mistake to add rmaps in the "freeze" (insert migration entries
prior to splitting huge page) case: the pmd_migration case already avoids
doing that, so just follow its lead. page_add_ref() versus put_page()
likewise. But why is one more put_page() needed in the "freeze" case?
Because it's removing the pmd rmap, already removed when pmd_migration
(and freeze and pmd_migration are mutually exclusive cases).
Link: https://lkml.kernel.org/r/d43748aa-fece-e0b9-c4ab-f23c9ebc9011@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Can the lock_compound_mapcount() bit_spin_lock apparatus be removed now?
Yes. Not by atomic64_t or cmpxchg games, those get difficult on 32-bit;
but if we slightly abuse subpages_mapcount by additionally demanding that
one bit be set there when the compound page is PMD-mapped, then a cascade
of two atomic ops is able to maintain the stats without bit_spin_lock.
This is harder to reason about than when bit_spin_locked, but I believe
safe; and no drift in stats detected when testing. When there are racing
removes and adds, of course the sequence of operations is less well-
defined; but each operation on subpages_mapcount is atomically good. What
might be disastrous, is if subpages_mapcount could ever fleetingly appear
negative: but the pte lock (or pmd lock) these rmap functions are called
under, ensures that a last remove cannot race ahead of a first add.
Continue to make an exception for hugetlb (PageHuge) pages, though that
exception can be easily removed by a further commit if necessary: leave
subpages_mapcount 0, don't bother with COMPOUND_MAPPED in its case, just
carry on checking compound_mapcount too in folio_mapped(), page_mapped().
Evidence is that this way goes slightly faster than the previous
implementation in all cases (pmds after ptes now taking around 103ms); and
relieves us of worrying about contention on the bit_spin_lock.
Link: https://lkml.kernel.org/r/3978f3ca-5473-55a7-4e14-efea5968d892@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm,thp,rmap: rework the use of subpages_mapcount", v2.
This patch (of 3):
Following suggestion from Linus, instead of counting every PTE map of a
compound page in subpages_mapcount, just count how many of its subpages
are PTE-mapped: this yields the exact number needed for NR_ANON_MAPPED and
NR_FILE_MAPPED stats, without any need for a locked scan of subpages; and
requires updating the count less often.
This does then revert total_mapcount() and folio_mapcount() to needing a
scan of subpages; but they are inherently racy, and need no locking, so
Linus is right that the scans are much better done there. Plus (unlike in
6.1 and previous) subpages_mapcount lets us avoid the scan in the common
case of no PTE maps. And page_mapped() and folio_mapped() remain scanless
and just as efficient with the new meaning of subpages_mapcount: those are
the functions which I most wanted to remove the scan from.
The updated page_dup_compound_rmap() is no longer suitable for use by anon
THP's __split_huge_pmd_locked(); but page_add_anon_rmap() can be used for
that, so long as its VM_BUG_ON_PAGE(!PageLocked) is deleted.
Evidence is that this way goes slightly faster than the previous
implementation for most cases; but significantly faster in the (now
scanless) pmds after ptes case, which started out at 870ms and was brought
down to 495ms by the previous series, now takes around 105ms.
Link: https://lkml.kernel.org/r/a5849eca-22f1-3517-bf29-95d982242742@google.com
Link: https://lkml.kernel.org/r/eec17e16-4e1-7c59-f1bc-5bca90dac919@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Today with `hugetlb_free_vmemmap=on` the struct page memory that is freed
back to page allocator is as following: for a 2M hugetlb page it will reuse
the first 4K vmemmap page to remap the remaining 7 vmemmap pages, and for a
1G hugetlb it will remap the remaining 4095 vmemmap pages. Essentially,
that means that it breaks the first 4K of a potentially contiguous chunk of
memory of 32K (for 2M hugetlb pages) or 16M (for 1G hugetlb pages). For
this reason the memory that it's free back to page allocator cannot be used
for hugetlb to allocate huge pages of the same size, but rather only of a
smaller huge page size:
Trying to assign a 64G node to hugetlb (on a 128G 2node guest, each node
having 64G):
* Before allocation:
Free pages count per migrate type at order 0 1 2 3
4 5 6 7 8 9 10
...
Node 0, zone Normal, type Movable 340 100 32 15
1 2 0 0 0 1 15558
$ echo 32768 > /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages
$ cat /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages
31987
* After:
Node 0, zone Normal, type Movable 30893 32006 31515 7
0 0 0 0 0 0 0
Notice how the memory freed back are put back into 4K / 8K / 16K page
pools. And it allocates a total of 31987 pages (63974M).
To fix this behaviour rather than remapping second vmemmap page (thus
breaking the contiguous block of memory backing the struct pages)
repopulate the first vmemmap page with a new one. We allocate and copy
from the currently mapped vmemmap page, and then remap it later on.
The same algorithm works if there's a pre initialized walk::reuse_page
and the head page doesn't need to be skipped and instead we remap it
when the @addr being changed is the @reuse_addr.
The new head page is allocated in vmemmap_remap_free() given that on
restore there's no need for functional change. Note that, because right
now one hugepage is remapped at a time, thus only one free 4K page at a
time is needed to remap the head page. Should it fail to allocate said
new page, it reuses the one that's already mapped just like before. As a
result, for every 64G of contiguous hugepages it can give back 1G more
of contiguous memory per 64G, while needing in total 128M new 4K pages
(for 2M hugetlb) or 256k (for 1G hugetlb).
After the changes, try to assign a 64G node to hugetlb (on a 128G 2node
guest, each node with 64G):
* Before allocation
Free pages count per migrate type at order 0 1 2 3
4 5 6 7 8 9 10
...
Node 0, zone Normal, type Movable 1 1 1 0
0 1 0 0 1 1 15564
$ echo 32768 > /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages
$ cat /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages
32394
* After:
Node 0, zone Normal, type Movable 0 50 97 108
96 81 70 46 18 0 0
In the example above, 407 more hugeltb 2M pages are allocated i.e. 814M out
of the 32394 (64788M) allocated. So the memory freed back is indeed being
used back in hugetlb and there's no massive order-0..order-2 pages
accumulated unused.
[joao.m.martins@oracle.com: v3]
Link: https://lkml.kernel.org/r/20221109200623.96867-1-joao.m.martins@oracle.com
[joao.m.martins@oracle.com: add smp_wmb() to ensure page contents are visible prior to PTE write]
Link: https://lkml.kernel.org/r/20221110121214.6297-1-joao.m.martins@oracle.com
Link: https://lkml.kernel.org/r/20221107153922.77094-1-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Commit ("mm,thp,rmap: lock_compound_mapcounts() on THP mapcounts")
propagated the "if (compound) {lock} else if (PageCompound) {lock} else
{atomic}" pattern throughout; but Linus hated the way that gives primacy
to the uncommon case: switch to "if (!PageCompound) {atomic} else if
(compound) {lock} else {lock}" throughout. Linus has a bigger idea for
how to improve it all, but here just make that rearrangement.
Link: https://lkml.kernel.org/r/fca2f694-2098-b0ef-d4e-f1d8b94d318c@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Fix the races in maintaining compound_mapcount, subpages_mapcount and
subpage _mapcount by using PG_locked in the first tail of any compound
page for a bit_spin_lock() on such modifications; skipping the usual
atomic operations on those fields in this case.
Bring page_remove_file_rmap() and page_remove_anon_compound_rmap() back
into page_remove_rmap() itself. Rearrange page_add_anon_rmap() and
page_add_file_rmap() and page_remove_rmap() to follow the same "if
(compound) {lock} else if (PageCompound) {lock} else {atomic}" pattern
(with a PageTransHuge in the compound test, like before, to avoid BUG_ONs
and optimize away that block when THP is not configured). Move all the
stats updates outside, after the bit_spin_locked section, so that it is
sure to be a leaf lock.
Add page_dup_compound_rmap() to manage compound locking versus atomics in
sync with the rest. In particular, hugetlb pages are still using the
atomics: to avoid unnecessary interference there, and because they never
have subpage mappings; but this exception can easily be changed.
Conveniently, page_dup_compound_rmap() turns out to suit an anon THP's
__split_huge_pmd_locked() too.
bit_spin_lock() is not popular with PREEMPT_RT folks: but PREEMPT_RT
sensibly excludes TRANSPARENT_HUGEPAGE already, so its only exposure is to
the non-hugetlb non-THP pte-mapped compound pages (with large folios being
currently dependent on TRANSPARENT_HUGEPAGE). There is never any scan of
subpages in this case; but we have chosen to use PageCompound tests rather
than PageTransCompound tests to gate the use of lock_compound_mapcounts(),
so that page_mapped() is correct on all compound pages, whether or not
TRANSPARENT_HUGEPAGE is enabled: could that be a problem for PREEMPT_RT,
when there is contention on the lock - under heavy concurrent forking for
example? If so, then it can be turned into a sleeping lock (like
folio_lock()) when PREEMPT_RT.
A simple 100 X munmap(mmap(2GB, MAP_SHARED|MAP_POPULATE, tmpfs), 2GB) took
18 seconds on small pages, and used to take 1 second on huge pages, but
now takes 115 milliseconds on huge pages. Mapping by pmds a second time
used to take 860ms and now takes 86ms; mapping by pmds after mapping by
ptes (when the scan is needed) used to take 870ms and now takes 495ms.
Mapping huge pages by ptes is largely unaffected but variable: between 5%
faster and 5% slower in what I've recorded. Contention on the lock is
likely to behave worse than contention on the atomics behaved.
Link: https://lkml.kernel.org/r/1b42bd1a-8223-e827-602f-d466c2db7d3c@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Compound page (folio) mapcount calculations have been different for anon
and file (or shmem) THPs, and involved the obscure PageDoubleMap flag.
And each huge mapping and unmapping of a file (or shmem) THP involved
atomically incrementing and decrementing the mapcount of every subpage of
that huge page, dirtying many struct page cachelines.
Add subpages_mapcount field to the struct folio and first tail page, so
that the total of subpage mapcounts is available in one place near the
head: then page_mapcount() and total_mapcount() and page_mapped(), and
their folio equivalents, are so quick that anon and file and hugetlb don't
need to be optimized differently. Delete the unloved PageDoubleMap.
page_add and page_remove rmap functions must now maintain the
subpages_mapcount as well as the subpage _mapcount, when dealing with pte
mappings of huge pages; and correct maintenance of NR_ANON_MAPPED and
NR_FILE_MAPPED statistics still needs reading through the subpages, using
nr_subpages_unmapped() - but only when first or last pmd mapping finds
subpages_mapcount raised (double-map case, not the common case).
But are those counts (used to decide when to split an anon THP, and in
vmscan's pagecache_reclaimable heuristic) correctly maintained? Not
quite: since page_remove_rmap() (and also split_huge_pmd()) is often
called without page lock, there can be races when a subpage pte mapcount
0<->1 while compound pmd mapcount 0<->1 is scanning - races which the
previous implementation had prevented. The statistics might become
inaccurate, and even drift down until they underflow through 0. That is
not good enough, but is better dealt with in a followup patch.
Update a few comments on first and second tail page overlaid fields.
hugepage_add_new_anon_rmap() has to "increment" compound_mapcount, but
subpages_mapcount and compound_pincount are already correctly at 0, so
delete its reinitialization of compound_pincount.
A simple 100 X munmap(mmap(2GB, MAP_SHARED|MAP_POPULATE, tmpfs), 2GB) took
18 seconds on small pages, and used to take 1 second on huge pages, but
now takes 119 milliseconds on huge pages. Mapping by pmds a second time
used to take 860ms and now takes 92ms; mapping by pmds after mapping by
ptes (when the scan is needed) used to take 870ms and now takes 495ms.
But there might be some benchmarks which would show a slowdown, because
tail struct pages now fall out of cache until final freeing checks them.
Link: https://lkml.kernel.org/r/47ad693-717-79c8-e1ba-46c3a6602e48@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm,huge,rmap: unify and speed up compound mapcounts".
This patch (of 3):
We want to declare one more int in the first tail of a compound page: that
first tail page being valuable property, since every compound page has a
first tail, but perhaps no more than that.
No problem on 64-bit: there is already space for it. No problem with
32-bit THPs: 5.18 commit 5232c63f46 ("mm: Make compound_pincount always
available") kindly cleared the space for it, apparently not realizing that
only 64-bit architectures enable CONFIG_THP_SWAP (whose use of tail
page->private might conflict) - but make sure of that in its Kconfig.
But hugetlb pages use tail page->private of the first tail page for a
subpool pointer, which will conflict; and they also use page->private of
the 2nd, 3rd and 4th tails.
Undo "mm: add private field of first tail to struct page and struct
folio"'s recent addition of private_1 to the folio tail: instead add
hugetlb_subpool, hugetlb_cgroup, hugetlb_cgroup_rsvd, hugetlb_hwpoison to
a second tail page of the folio: THP has long been using several fields of
that tail, so make better use of it for hugetlb too. This is not how a
generic folio should be declared in future, but it is an effective
transitional way to make use of it.
Delete the SUBPAGE_INDEX stuff, but keep __NR_USED_SUBPAGE: now 3.
[hughd@google.com: prefix folio's page_1 and page_2 with double underscore,
give folio's _flags_2 and _head_2 a line documentation each]
Link: https://lkml.kernel.org/r/9e2cb6b-5b58-d3f2-b5ee-5f8a14e8f10@google.com
Link: https://lkml.kernel.org/r/5f52de70-975-e94f-f141-543765736181@google.com
Link: https://lkml.kernel.org/r/3818cc9a-9999-d064-d778-9c94c5911e6@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
