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Subject[PATCH 1/2] delayacct: support re-entrance detection of thrashing accounting
Date
From: Yang Yang <yang.yang29@zte.com.cn>

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 aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU")

Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: CGEL ZTE <cgel.zte@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: wangyong <wang.yong12@zte.com.cn>
---
include/linux/delayacct.h | 16 ++++++++--------
include/linux/sched.h | 4 ++++
kernel/delayacct.c | 13 +++++++++++--
mm/filemap.c | 10 ++++++----
4 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/include/linux/delayacct.h b/include/linux/delayacct.h
index 58aea2d7385c..aeb76f1c894e 100644
--- a/include/linux/delayacct.h
+++ b/include/linux/delayacct.h
@@ -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(unsigned long *flags);
+extern void __delayacct_thrashing_end(unsigned long *flags);
extern void __delayacct_swapin_start(void);
extern void __delayacct_swapin_end(void);
extern void __delayacct_compact_start(void);
@@ -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(unsigned long *flags)
{
if (!static_branch_unlikely(&delayacct_key))
return;

if (current->delays)
- __delayacct_thrashing_start();
+ __delayacct_thrashing_start(flags);
}

-static inline void delayacct_thrashing_end(void)
+static inline void delayacct_thrashing_end(unsigned long *flags)
{
if (!static_branch_unlikely(&delayacct_key))
return;

if (current->delays)
- __delayacct_thrashing_end();
+ __delayacct_thrashing_end(flags);
}

static inline void delayacct_swapin_start(void)
@@ -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(unsigned long *flags)
{}
-static inline void delayacct_thrashing_end(void)
+static inline void delayacct_thrashing_end(unsigned long *flags)
{}
static inline void delayacct_swapin_start(void)
{}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d6b0866c71ed..5fb942e29583 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -943,6 +943,10 @@ 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. */

diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index 164ed9ef77a3..a5916196022f 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -214,13 +214,22 @@ void __delayacct_freepages_end(void)
&current->delays->freepages_count);
}

-void __delayacct_thrashing_start(void)
+void __delayacct_thrashing_start(unsigned long *flags)
{
+ *flags = current->in_thrashing;
+ if (*flags)
+ return;
+
+ current->in_thrashing = 1;
current->delays->thrashing_start = local_clock();
}

-void __delayacct_thrashing_end(void)
+void __delayacct_thrashing_end(unsigned long *flags)
{
+ if (*flags)
+ return;
+
+ current->in_thrashing = 0;
delayacct_end(&current->delays->lock,
&current->delays->thrashing_start,
&current->delays->thrashing_delay,
diff --git a/mm/filemap.c b/mm/filemap.c
index cfe15e89b3c2..92ceebc75900 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -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;
+ unsigned long dflags;

if (bit_nr == PG_locked &&
!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
- delayacct_thrashing_start();
+ delayacct_thrashing_start(&dflags);
psi_memstall_enter(&pflags);
thrashing = true;
}
@@ -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(&dflags);
psi_memstall_leave(&pflags);
}

@@ -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;
+ unsigned long dflags;
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(&dflags);
psi_memstall_enter(&pflags);
thrashing = true;
}
@@ -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(&dflags);
psi_memstall_leave(&pflags);
}
}
--
2.25.1
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