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delayacct: track delays from write-protect copy

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Delay accounting does not track the delay of write-protect copy.  When
tasks trigger many write-protect copys(include COW and unsharing of
anonymous pages[1]), it may spend a amount of time waiting for them.  To
get the delay of tasks in write-protect copy, could help users to evaluate
the impact of using KSM or fork() or GUP.

Also update tools/accounting/getdelays.c:

    / # ./getdelays -dl -p 231
    print delayacct stats ON
    listen forever
    PID     231

    CPU             count     real total  virtual total    delay total  delay average
                     6247     1859000000     2154070021     1674255063          0.268ms
    IO              count    delay total  delay average
                        0              0              0ms
    SWAP            count    delay total  delay average
                        0              0              0ms
    RECLAIM         count    delay total  delay average
                        0              0              0ms
    THRASHING       count    delay total  delay average
                        0              0              0ms
    COMPACT         count    delay total  delay average
                        3          72758              0ms
    WPCOPY          count    delay total  delay average
                     3635      271567604              0ms

[1] commit 31cc5bc4af70("mm: support GUP-triggered unsharing of anonymous pages")

Link: https://lkml.kernel.org/r/20220409014342.2505532-1-yang.yang29@zte.com.cn
Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Jiang Xuexin <jiang.xuexin@zte.com.cn>
Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: wangyong <wang.yong12@zte.com.cn>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Yang Yang 2022-06-01 15:55:25 -07:00 committed by akpm
parent 54eb8462f2
commit 662ce1dc9c
7 changed files with 76 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
Documentation/accounting/delay-accounting.rst
View File

@ -15,6 +15,7 @@ c) swapping in pages
d) memory reclaim
e) thrashing page cache
f) direct compact
g) write-protect copy
and makes these statistics available to userspace through
the taskstats interface.
@ -48,7 +49,7 @@ this structure. See
for a description of the fields pertaining to delay accounting.
It will generally be in the form of counters returning the cumulative
delay seen for cpu, sync block I/O, swapin, memory reclaim, thrash page
cache, direct compact etc.
cache, direct compact, write-protect copy etc.
Taking the difference of two successive readings of a given
counter (say cpu_delay_total) for a task will give the delay
@ -117,6 +118,8 @@ Get sum of delays, since system boot, for all pids with tgid 5::
0 0 0ms
COMPACT count delay total delay average
0 0 0ms
WPCOPY count delay total delay average
0 0 0ms
Get IO accounting for pid 1, it works only with -p::

28
include/linux/delayacct.h
View File

@ -45,9 +45,13 @@ struct task_delay_info {
u64 compact_start;
u64 compact_delay; /* wait for memory compact */
u64 wpcopy_start;
u64 wpcopy_delay; /* wait for write-protect copy */
u32 freepages_count; /* total count of memory reclaim */
u32 thrashing_count; /* total count of thrash waits */
u32 compact_count; /* total count of memory compact */
u32 wpcopy_count; /* total count of write-protect copy */
};
#endif
@ -75,6 +79,8 @@ extern void __delayacct_swapin_start(void);
extern void __delayacct_swapin_end(void);
extern void __delayacct_compact_start(void);
extern void __delayacct_compact_end(void);
extern void __delayacct_wpcopy_start(void);
extern void __delayacct_wpcopy_end(void);
static inline void delayacct_tsk_init(struct task_struct *tsk)
{
@ -191,6 +197,24 @@ static inline void delayacct_compact_end(void)
__delayacct_compact_end();
}
static inline void delayacct_wpcopy_start(void)
{
if (!static_branch_unlikely(&delayacct_key))
return;
if (current->delays)
__delayacct_wpcopy_start();
}
static inline void delayacct_wpcopy_end(void)
{
if (!static_branch_unlikely(&delayacct_key))
return;
if (current->delays)
__delayacct_wpcopy_end();
}
#else
static inline void delayacct_init(void)
{}
@ -225,6 +249,10 @@ static inline void delayacct_compact_start(void)
{}
static inline void delayacct_compact_end(void)
{}
static inline void delayacct_wpcopy_start(void)
{}
static inline void delayacct_wpcopy_end(void)
{}
#endif /* CONFIG_TASK_DELAY_ACCT */

6
include/uapi/linux/taskstats.h
View File

@ -34,7 +34,7 @@
*/
#define TASKSTATS_VERSION 12
#define TASKSTATS_VERSION 13
#define TS_COMM_LEN 32 /* should be >= TASK_COMM_LEN
* in linux/sched.h */
@ -194,6 +194,10 @@ struct taskstats {
__u64 ac_exe_dev; /* program binary device ID */
__u64 ac_exe_inode; /* program binary inode number */
/* v12 end */
/* v13: Delay waiting for write-protect copy */
__u64 wpcopy_count;
__u64 wpcopy_delay_total;
};

16
kernel/delayacct.c
View File

@ -177,11 +177,14 @@ int delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
d->thrashing_delay_total = (tmp < d->thrashing_delay_total) ? 0 : tmp;
tmp = d->compact_delay_total + tsk->delays->compact_delay;
d->compact_delay_total = (tmp < d->compact_delay_total) ? 0 : tmp;
tmp = d->wpcopy_delay_total + tsk->delays->wpcopy_delay;
d->wpcopy_delay_total = (tmp < d->wpcopy_delay_total) ? 0 : tmp;
d->blkio_count += tsk->delays->blkio_count;
d->swapin_count += tsk->delays->swapin_count;
d->freepages_count += tsk->delays->freepages_count;
d->thrashing_count += tsk->delays->thrashing_count;
d->compact_count += tsk->delays->compact_count;
d->wpcopy_count += tsk->delays->wpcopy_count;
raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
return 0;
@ -249,3 +252,16 @@ void __delayacct_compact_end(void)
&current->delays->compact_delay,
&current->delays->compact_count);
}
void __delayacct_wpcopy_start(void)
{
current->delays->wpcopy_start = local_clock();
}
void __delayacct_wpcopy_end(void)
{
delayacct_end(&current->delays->lock,
&current->delays->wpcopy_start,
&current->delays->wpcopy_delay,
&current->delays->wpcopy_count);
}

8
mm/hugetlb.c
View File

@ -32,6 +32,7 @@
#include <linux/cma.h>
#include <linux/migrate.h>
#include <linux/nospec.h>
#include <linux/delayacct.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
@ -5230,6 +5231,8 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
pte = huge_ptep_get(ptep);
old_page = pte_page(pte);
delayacct_wpcopy_start();
retry_avoidcopy:
/*
* If no-one else is actually using this page, we're the exclusive
@ -5240,6 +5243,8 @@ retry_avoidcopy:
page_move_anon_rmap(old_page, vma);
if (likely(!unshare))
set_huge_ptep_writable(vma, haddr, ptep);
delayacct_wpcopy_end();
return 0;
}
VM_BUG_ON_PAGE(PageAnon(old_page) && PageAnonExclusive(old_page),
@ -5309,6 +5314,7 @@ retry_avoidcopy:
* race occurs while re-acquiring page table
* lock, and our job is done.
*/
delayacct_wpcopy_end();
return 0;
}
@ -5367,6 +5373,8 @@ out_release_old:
put_page(old_page);
spin_lock(ptl); /* Caller expects lock to be held */
delayacct_wpcopy_end();
return ret;
}

8
mm/memory.c
View File

@ -3090,6 +3090,8 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
int page_copied = 0;
struct mmu_notifier_range range;
delayacct_wpcopy_start();
if (unlikely(anon_vma_prepare(vma)))
goto oom;
@ -3114,6 +3116,8 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
put_page(new_page);
if (old_page)
put_page(old_page);
delayacct_wpcopy_end();
return 0;
}
}
@ -3220,12 +3224,16 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
free_swap_cache(old_page);
put_page(old_page);
}
delayacct_wpcopy_end();
return (page_copied && !unshare) ? VM_FAULT_WRITE : 0;
oom_free_new:
put_page(new_page);
oom:
if (old_page)
put_page(old_page);
delayacct_wpcopy_end();
return VM_FAULT_OOM;
}

8
tools/accounting/getdelays.c
View File

@ -207,6 +207,8 @@ static void print_delayacct(struct taskstats *t)
"THRASHING%12s%15s%15s\n"
" %15llu%15llu%15llums\n"
"COMPACT %12s%15s%15s\n"
" %15llu%15llu%15llums\n"
"WPCOPY %12s%15s%15s\n"
" %15llu%15llu%15llums\n",
"count", "real total", "virtual total",
"delay total", "delay average",
@ -234,7 +236,11 @@ static void print_delayacct(struct taskstats *t)
"count", "delay total", "delay average",
(unsigned long long)t->compact_count,
(unsigned long long)t->compact_delay_total,
average_ms(t->compact_delay_total, t->compact_count));
average_ms(t->compact_delay_total, t->compact_count),
"count", "delay total", "delay average",
(unsigned long long)t->wpcopy_count,
(unsigned long long)t->wpcopy_delay_total,
average_ms(t->wpcopy_delay_total, t->wpcopy_count));
}
static void task_context_switch_counts(struct taskstats *t)