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Huang Ying c6ddfb6c58 mm, clear_huge_page: move order algorithm into a separate function 
Patch series "mm, huge page: Copy target sub-page last when copy huge
page", v2.

Huge page helps to reduce TLB miss rate, but it has higher cache
footprint, sometimes this may cause some issue.  For example, when
copying huge page on x86_64 platform, the cache footprint is 4M.  But on
a Xeon E5 v3 2699 CPU, there are 18 cores, 36 threads, and only 45M LLC
(last level cache).  That is, in average, there are 2.5M LLC for each
core and 1.25M LLC for each thread.

If the cache contention is heavy when copying the huge page, and we copy
the huge page from the begin to the end, it is possible that the begin
of huge page is evicted from the cache after we finishing copying the
end of the huge page.  And it is possible for the application to access
the begin of the huge page after copying the huge page.

In c79b57e462 ("mm: hugetlb: clear target sub-page last when clearing
huge page"), to keep the cache lines of the target subpage hot, the
order to clear the subpages in the huge page in clear_huge_page() is
changed to clearing the subpage which is furthest from the target
subpage firstly, and the target subpage last.  The similar order
changing helps huge page copying too.  That is implemented in this
patchset.

The patchset is a generic optimization which should benefit quite some
workloads, not for a specific use case.  To demonstrate the performance
benefit of the patchset, we have tested it with vm-scalability run on
transparent huge page.

With this patchset, the throughput increases ~16.6% in vm-scalability
anon-cow-seq test case with 36 processes on a 2 socket Xeon E5 v3 2699
system (36 cores, 72 threads).  The test case set
/sys/kernel/mm/transparent_hugepage/enabled to be always, mmap() a big
anonymous memory area and populate it, then forked 36 child processes,
each writes to the anonymous memory area from the begin to the end, so
cause copy on write.  For each child process, other child processes
could be seen as other workloads which generate heavy cache pressure.
At the same time, the IPC (instruction per cycle) increased from 0.63 to
0.78, and the time spent in user space is reduced ~7.2%.

This patch (of 4):

In c79b57e462 ("mm: hugetlb: clear target sub-page last when clearing
huge page"), to keep the cache lines of the target subpage hot, the
order to clear the subpages in the huge page in clear_huge_page() is
changed to clearing the subpage which is furthest from the target
subpage firstly, and the target subpage last.  This optimization could
be applied to copying huge page too with the same order algorithm.  To
avoid code duplication and reduce maintenance overhead, in this patch,
the order algorithm is moved out of clear_huge_page() into a separate
function: process_huge_page().  So that we can use it for copying huge
page too.

This will change the direct calls to clear_user_highpage() into the
indirect calls.  But with the proper inline support of the compilers,
the indirect call will be optimized to be the direct call.  Our tests
show no performance change with the patch.

This patch is a code cleanup without functionality change.

Link: http://lkml.kernel.org/r/20180524005851.4079-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Suggested-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Shaohua Li <shli@fb.com>
Cc: Christopher Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-17 16:20:29 -07:00
arch mm: convert return type of handle_mm_fault() caller to vm_fault_t 2018-08-17 16:20:28 -07:00
block for-4.19/block-20180812 2018-08-14 10:23:25 -07:00
certs Replace magic for trusting the secondary keyring with #define 2018-08-16 09:57:20 -07:00
crypto Replace magic for trusting the secondary keyring with #define 2018-08-16 09:57:20 -07:00
Documentation tools/vm/page-types.c: add support for idle page tracking 2018-08-17 16:20:28 -07:00
drivers mm: convert return type of handle_mm_fault() caller to vm_fault_t 2018-08-17 16:20:28 -07:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs ext4: readpages() should submit IO as read-ahead 2018-08-17 16:20:29 -07:00
include mpage: mpage_readpages() should submit IO as read-ahead 2018-08-17 16:20:29 -07:00
init Consolidation of Kconfig files by Christoph Hellwig. 2018-08-15 13:05:12 -07:00
ipc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-08-15 15:04:25 -07:00
kernel drm pull for 4.19-rc1 2018-08-15 17:39:07 -07:00
lib SCSI misc on 20180815 2018-08-15 22:06:26 -07:00
LICENSES LICENSES: Add Linux-OpenIB license text 2018-04-27 16:41:53 -06:00
mm mm, clear_huge_page: move order algorithm into a separate function 2018-08-17 16:20:29 -07:00
net Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-08-15 16:01:47 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-08-15 15:04:25 -07:00
scripts scripts: add Python 3 compatibility to spdxcheck.py 2018-08-17 16:20:27 -07:00
security Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2018-08-15 22:54:12 -07:00
sound ALSA: update dell-wmi mic-mute registration to new world order 2018-08-15 19:08:10 -07:00
tools tools/vm/page-types.c: add support for idle page tracking 2018-08-17 16:20:28 -07:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt arm64 updates for 4.19 2018-08-14 16:39:13 -07:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap mailmap: remap some of my email addresses to kernel.org address 2018-08-06 13:15:16 -04:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS 9p: add Dominique Martinet to MAINTAINERS 2018-08-17 16:20:27 -07:00
Makefile Kconfig updates for v4.19 2018-08-15 12:50:10 -07:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.