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delayacct: support re-entrance detection of thrashing accounting
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Once upon a time, we only support accounting thrashing of page cache. 
Then Joonsoo introduced workingset detection for anonymous pages and we
gained the ability to account thrashing of them[1].

For page cache thrashing accounting, there is no suitable place to do it
in fs level likes swap_readpage().  So we have to do it in
folio_wait_bit_common().

Then for anonymous pages thrashing accounting, we have to do it in both
swap_readpage() and folio_wait_bit_common().  This likes PSI, so we should
let thrashing accounting supports re-entrance detection.

This patch is to prepare complete thrashing accounting, and is based on
patch "filemap: make the accounting of thrashing more consistent".

[1] commit aae466b ("mm/swap: implement workingset detection for anonymous LRU")

Link: https://lkml.kernel.org/r/20220815071134.74551-1-yang.yang29@zte.com.cn
Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: CGEL ZTE <cgel.zte@gmail.com>
Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: wangyong <wang.yong12@zte.com.cn>
Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@yangyang20220519 @akpm00
yangyang20220519 authored and akpm00 committed Sep 27, 2022
1 parent 7047b5a commit aa1cf99
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Showing 4 changed files with 29 additions and 14 deletions.
16 changes: 8 additions & 8 deletions include/linux/delayacct.h
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Original file line number Diff line number Diff line change
Expand Up @@ -73,8 +73,8 @@ extern int delayacct_add_tsk(struct taskstats *, struct task_struct *);
extern __u64 __delayacct_blkio_ticks(struct task_struct *);
extern void __delayacct_freepages_start(void);
extern void __delayacct_freepages_end(void);
extern void __delayacct_thrashing_start(void);
extern void __delayacct_thrashing_end(void);
extern void __delayacct_thrashing_start(bool *in_thrashing);
extern void __delayacct_thrashing_end(bool *in_thrashing);
extern void __delayacct_swapin_start(void);
extern void __delayacct_swapin_end(void);
extern void __delayacct_compact_start(void);
Expand Down Expand Up @@ -143,22 +143,22 @@ static inline void delayacct_freepages_end(void)
__delayacct_freepages_end();
}

static inline void delayacct_thrashing_start(void)
static inline void delayacct_thrashing_start(bool *in_thrashing)
{
if (!static_branch_unlikely(&delayacct_key))
return;

if (current->delays)
__delayacct_thrashing_start();
__delayacct_thrashing_start(in_thrashing);
}

static inline void delayacct_thrashing_end(void)
static inline void delayacct_thrashing_end(bool *in_thrashing)
{
if (!static_branch_unlikely(&delayacct_key))
return;

if (current->delays)
__delayacct_thrashing_end();
__delayacct_thrashing_end(in_thrashing);
}

static inline void delayacct_swapin_start(void)
Expand Down Expand Up @@ -237,9 +237,9 @@ static inline void delayacct_freepages_start(void)
{}
static inline void delayacct_freepages_end(void)
{}
static inline void delayacct_thrashing_start(void)
static inline void delayacct_thrashing_start(bool *in_thrashing)
{}
static inline void delayacct_thrashing_end(void)
static inline void delayacct_thrashing_end(bool *in_thrashing)
{}
static inline void delayacct_swapin_start(void)
{}
Expand Down
4 changes: 4 additions & 0 deletions include/linux/sched.h
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Original file line number Diff line number Diff line change
Expand Up @@ -944,6 +944,10 @@ struct task_struct {
#ifdef CONFIG_CPU_SUP_INTEL
unsigned reported_split_lock:1;
#endif
#ifdef CONFIG_TASK_DELAY_ACCT
/* delay due to memory thrashing */
unsigned in_thrashing:1;
#endif

unsigned long atomic_flags; /* Flags requiring atomic access. */

Expand Down
13 changes: 11 additions & 2 deletions kernel/delayacct.c
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Original file line number Diff line number Diff line change
Expand Up @@ -214,13 +214,22 @@ void __delayacct_freepages_end(void)
&current->delays->freepages_count);
}

void __delayacct_thrashing_start(void)
void __delayacct_thrashing_start(bool *in_thrashing)
{
*in_thrashing = !!current->in_thrashing;
if (*in_thrashing)
return;

current->in_thrashing = 1;
current->delays->thrashing_start = local_clock();
}

void __delayacct_thrashing_end(void)
void __delayacct_thrashing_end(bool *in_thrashing)
{
if (*in_thrashing)
return;

current->in_thrashing = 0;
delayacct_end(&current->delays->lock,
&current->delays->thrashing_start,
&current->delays->thrashing_delay,
Expand Down
10 changes: 6 additions & 4 deletions mm/filemap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1222,10 +1222,11 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
wait_queue_entry_t *wait = &wait_page.wait;
bool thrashing = false;
unsigned long pflags;
bool in_thrashing;

if (bit_nr == PG_locked &&
!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
delayacct_thrashing_start();
delayacct_thrashing_start(&in_thrashing);
psi_memstall_enter(&pflags);
thrashing = true;
}
Expand Down Expand Up @@ -1325,7 +1326,7 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
finish_wait(q, wait);

if (thrashing) {
delayacct_thrashing_end();
delayacct_thrashing_end(&in_thrashing);
psi_memstall_leave(&pflags);
}

Expand Down Expand Up @@ -1374,12 +1375,13 @@ void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
wait_queue_entry_t *wait = &wait_page.wait;
bool thrashing = false;
unsigned long pflags;
bool in_thrashing;
wait_queue_head_t *q;
struct folio *folio = page_folio(pfn_swap_entry_to_page(entry));

q = folio_waitqueue(folio);
if (!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
delayacct_thrashing_start();
delayacct_thrashing_start(&in_thrashing);
psi_memstall_enter(&pflags);
thrashing = true;
}
Expand Down Expand Up @@ -1426,7 +1428,7 @@ void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
finish_wait(q, wait);

if (thrashing) {
delayacct_thrashing_end();
delayacct_thrashing_end(&in_thrashing);
psi_memstall_leave(&pflags);
}
}
Expand Down

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