It doesn't need to wait for checkpoint being completed triggered by end_io.
[ 20.157753] ------------[ cut here ]------------
[ 20.158393] do not call blocking ops when !TASK_RUNNING; state=2 set at [<0000000096354225>] prepare_to_wait+0xcd/0x430
[ 20.159858] WARNING: CPU: 1 PID: 1152 at kernel/sched/core.c:7142 __might_sleep+0x149/0x1a0
...
[ 20.176110] __submit_merged_write_cond+0x191/0x310
[ 20.176739] f2fs_submit_merged_write+0x18/0x20
[ 20.177323] f2fs_wait_on_all_pages+0x269/0x2d0
[ 20.177899] ? block_operations+0x980/0x980
[ 20.178441] ? __kasan_check_read+0x11/0x20
[ 20.178975] ? finish_wait+0x260/0x260
[ 20.179488] ? percpu_counter_set+0x147/0x230
[ 20.180049] do_checkpoint+0x1757/0x2a50
[ 20.180558] f2fs_write_checkpoint+0x840/0xaf0
[ 20.181126] f2fs_sync_fs+0x287/0x4a0
Reported-by: Eric Biggers <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>
---
fs/f2fs/checkpoint.c | 6 +-----
fs/f2fs/data.c | 4 ----
fs/f2fs/f2fs.h | 1 -
fs/f2fs/super.c | 1 -
4 files changed, 1 insertion(+), 11 deletions(-)
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 99c8061da55b9..2bdddc725e677 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1255,11 +1255,7 @@ static void unblock_operations(struct f2fs_sb_info *sbi)
void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
{
- DEFINE_WAIT(wait);
-
for (;;) {
- prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
-
if (!get_pages(sbi, type))
break;
@@ -1271,9 +1267,9 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
FS_CP_META_IO);
else if (type == F2FS_WB_CP_DATA)
f2fs_submit_merged_write(sbi, DATA);
+
io_schedule_timeout(DEFAULT_IO_TIMEOUT);
}
- finish_wait(&sbi->cp_wait, &wait);
}
static void update_ckpt_flags(struct f2fs_sb_info *sbi, struct cp_control *cpc)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index c1b676be67b9a..588d2871bbe69 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -383,10 +383,6 @@ static void f2fs_write_end_io(struct bio *bio)
clear_cold_data(page);
end_page_writeback(page);
}
- if (!get_pages(sbi, F2FS_WB_CP_DATA) &&
- wq_has_sleeper(&sbi->cp_wait))
- wake_up(&sbi->cp_wait);
-
bio_put(bio);
}
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 02811ce15059b..a036539363030 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1437,7 +1437,6 @@ struct f2fs_sb_info {
struct rw_semaphore cp_rwsem; /* blocking FS operations */
struct rw_semaphore node_write; /* locking node writes */
struct rw_semaphore node_change; /* locking node change */
- wait_queue_head_t cp_wait;
unsigned long last_time[MAX_TIME]; /* to store time in jiffies */
long interval_time[MAX_TIME]; /* to store thresholds */
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 83bf9a02f83f2..5f4d9abc079d6 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3540,7 +3540,6 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
init_rwsem(&sbi->cp_rwsem);
init_rwsem(&sbi->quota_sem);
- init_waitqueue_head(&sbi->cp_wait);
init_sb_info(sbi);
err = init_percpu_info(sbi);
--
2.28.0.163.g6104cc2f0b6-goog
On 2020/8/4 1:28, Jaegeuk Kim wrote:
> It doesn't need to wait for checkpoint being completed triggered by end_io.
>
> [ 20.157753] ------------[ cut here ]------------
> [ 20.158393] do not call blocking ops when !TASK_RUNNING; state=2 set at [<0000000096354225>] prepare_to_wait+0xcd/0x430
> [ 20.159858] WARNING: CPU: 1 PID: 1152 at kernel/sched/core.c:7142 __might_sleep+0x149/0x1a0
> ...
> [ 20.176110] __submit_merged_write_cond+0x191/0x310
> [ 20.176739] f2fs_submit_merged_write+0x18/0x20
> [ 20.177323] f2fs_wait_on_all_pages+0x269/0x2d0
> [ 20.177899] ? block_operations+0x980/0x980
> [ 20.178441] ? __kasan_check_read+0x11/0x20
> [ 20.178975] ? finish_wait+0x260/0x260
> [ 20.179488] ? percpu_counter_set+0x147/0x230
> [ 20.180049] do_checkpoint+0x1757/0x2a50
> [ 20.180558] f2fs_write_checkpoint+0x840/0xaf0
> [ 20.181126] f2fs_sync_fs+0x287/0x4a0
>
> Reported-by: Eric Biggers <[email protected]>
> Signed-off-by: Jaegeuk Kim <[email protected]>
> ---
> fs/f2fs/checkpoint.c | 6 +-----
> fs/f2fs/data.c | 4 ----
> fs/f2fs/f2fs.h | 1 -
> fs/f2fs/super.c | 1 -
> 4 files changed, 1 insertion(+), 11 deletions(-)
>
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 99c8061da55b9..2bdddc725e677 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -1255,11 +1255,7 @@ static void unblock_operations(struct f2fs_sb_info *sbi)
>
> void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
> {
> - DEFINE_WAIT(wait);
> -
> for (;;) {
> - prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
Wouldn't that case high cpu usage before io end?
> -
> if (!get_pages(sbi, type))
> break;
>
> @@ -1271,9 +1267,9 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
> FS_CP_META_IO);
> else if (type == F2FS_WB_CP_DATA)
> f2fs_submit_merged_write(sbi, DATA);
> +
> io_schedule_timeout(DEFAULT_IO_TIMEOUT);
> }
> - finish_wait(&sbi->cp_wait, &wait);
> }
>
> static void update_ckpt_flags(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index c1b676be67b9a..588d2871bbe69 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -383,10 +383,6 @@ static void f2fs_write_end_io(struct bio *bio)
> clear_cold_data(page);
> end_page_writeback(page);
> }
> - if (!get_pages(sbi, F2FS_WB_CP_DATA) &&
> - wq_has_sleeper(&sbi->cp_wait))
> - wake_up(&sbi->cp_wait);
> -
> bio_put(bio);
> }
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 02811ce15059b..a036539363030 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1437,7 +1437,6 @@ struct f2fs_sb_info {
> struct rw_semaphore cp_rwsem; /* blocking FS operations */
> struct rw_semaphore node_write; /* locking node writes */
> struct rw_semaphore node_change; /* locking node change */
> - wait_queue_head_t cp_wait;
> unsigned long last_time[MAX_TIME]; /* to store time in jiffies */
> long interval_time[MAX_TIME]; /* to store thresholds */
>
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 83bf9a02f83f2..5f4d9abc079d6 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -3540,7 +3540,6 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>
> init_rwsem(&sbi->cp_rwsem);
> init_rwsem(&sbi->quota_sem);
> - init_waitqueue_head(&sbi->cp_wait);
> init_sb_info(sbi);
>
> err = init_percpu_info(sbi);
>
On 08/04, Chao Yu wrote:
> On 2020/8/4 1:28, Jaegeuk Kim wrote:
> > It doesn't need to wait for checkpoint being completed triggered by end_io.
> >
> > [ 20.157753] ------------[ cut here ]------------
> > [ 20.158393] do not call blocking ops when !TASK_RUNNING; state=2 set at [<0000000096354225>] prepare_to_wait+0xcd/0x430
> > [ 20.159858] WARNING: CPU: 1 PID: 1152 at kernel/sched/core.c:7142 __might_sleep+0x149/0x1a0
> > ...
> > [ 20.176110] __submit_merged_write_cond+0x191/0x310
> > [ 20.176739] f2fs_submit_merged_write+0x18/0x20
> > [ 20.177323] f2fs_wait_on_all_pages+0x269/0x2d0
> > [ 20.177899] ? block_operations+0x980/0x980
> > [ 20.178441] ? __kasan_check_read+0x11/0x20
> > [ 20.178975] ? finish_wait+0x260/0x260
> > [ 20.179488] ? percpu_counter_set+0x147/0x230
> > [ 20.180049] do_checkpoint+0x1757/0x2a50
> > [ 20.180558] f2fs_write_checkpoint+0x840/0xaf0
> > [ 20.181126] f2fs_sync_fs+0x287/0x4a0
> >
> > Reported-by: Eric Biggers <[email protected]>
> > Signed-off-by: Jaegeuk Kim <[email protected]>
> > ---
> > fs/f2fs/checkpoint.c | 6 +-----
> > fs/f2fs/data.c | 4 ----
> > fs/f2fs/f2fs.h | 1 -
> > fs/f2fs/super.c | 1 -
> > 4 files changed, 1 insertion(+), 11 deletions(-)
> >
> > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > index 99c8061da55b9..2bdddc725e677 100644
> > --- a/fs/f2fs/checkpoint.c
> > +++ b/fs/f2fs/checkpoint.c
> > @@ -1255,11 +1255,7 @@ static void unblock_operations(struct f2fs_sb_info *sbi)
> > void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
> > {
> > - DEFINE_WAIT(wait);
> > -
> > for (;;) {
> > - prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
>
> Wouldn't that case high cpu usage before io end?
This is a critical path to wait for IO completion in checkpoint, which would be
better to wait for it to avoid long latency to continue filesystem operations.
Moreover, I expect io_schedule_timeout() can mitigate such the CPU overhead and
actually we don't need to make there-in context switches as well.
>
> > -
> > if (!get_pages(sbi, type))
> > break;
> > @@ -1271,9 +1267,9 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
> > FS_CP_META_IO);
> > else if (type == F2FS_WB_CP_DATA)
> > f2fs_submit_merged_write(sbi, DATA);
> > +
> > io_schedule_timeout(DEFAULT_IO_TIMEOUT);
> > }
> > - finish_wait(&sbi->cp_wait, &wait);
> > }
> > static void update_ckpt_flags(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index c1b676be67b9a..588d2871bbe69 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -383,10 +383,6 @@ static void f2fs_write_end_io(struct bio *bio)
> > clear_cold_data(page);
> > end_page_writeback(page);
> > }
> > - if (!get_pages(sbi, F2FS_WB_CP_DATA) &&
> > - wq_has_sleeper(&sbi->cp_wait))
> > - wake_up(&sbi->cp_wait);
> > -
> > bio_put(bio);
> > }
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 02811ce15059b..a036539363030 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1437,7 +1437,6 @@ struct f2fs_sb_info {
> > struct rw_semaphore cp_rwsem; /* blocking FS operations */
> > struct rw_semaphore node_write; /* locking node writes */
> > struct rw_semaphore node_change; /* locking node change */
> > - wait_queue_head_t cp_wait;
> > unsigned long last_time[MAX_TIME]; /* to store time in jiffies */
> > long interval_time[MAX_TIME]; /* to store thresholds */
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 83bf9a02f83f2..5f4d9abc079d6 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -3540,7 +3540,6 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
> > init_rwsem(&sbi->cp_rwsem);
> > init_rwsem(&sbi->quota_sem);
> > - init_waitqueue_head(&sbi->cp_wait);
> > init_sb_info(sbi);
> > err = init_percpu_info(sbi);
> >
On 2020/8/4 9:04, Jaegeuk Kim wrote:
> On 08/04, Chao Yu wrote:
>> On 2020/8/4 1:28, Jaegeuk Kim wrote:
>>> It doesn't need to wait for checkpoint being completed triggered by end_io.
>>>
>>> [ 20.157753] ------------[ cut here ]------------
>>> [ 20.158393] do not call blocking ops when !TASK_RUNNING; state=2 set at [<0000000096354225>] prepare_to_wait+0xcd/0x430
>>> [ 20.159858] WARNING: CPU: 1 PID: 1152 at kernel/sched/core.c:7142 __might_sleep+0x149/0x1a0
>>> ...
>>> [ 20.176110] __submit_merged_write_cond+0x191/0x310
>>> [ 20.176739] f2fs_submit_merged_write+0x18/0x20
>>> [ 20.177323] f2fs_wait_on_all_pages+0x269/0x2d0
>>> [ 20.177899] ? block_operations+0x980/0x980
>>> [ 20.178441] ? __kasan_check_read+0x11/0x20
>>> [ 20.178975] ? finish_wait+0x260/0x260
>>> [ 20.179488] ? percpu_counter_set+0x147/0x230
>>> [ 20.180049] do_checkpoint+0x1757/0x2a50
>>> [ 20.180558] f2fs_write_checkpoint+0x840/0xaf0
>>> [ 20.181126] f2fs_sync_fs+0x287/0x4a0
>>>
>>> Reported-by: Eric Biggers <[email protected]>
>>> Signed-off-by: Jaegeuk Kim <[email protected]>
>>> ---
>>> fs/f2fs/checkpoint.c | 6 +-----
>>> fs/f2fs/data.c | 4 ----
>>> fs/f2fs/f2fs.h | 1 -
>>> fs/f2fs/super.c | 1 -
>>> 4 files changed, 1 insertion(+), 11 deletions(-)
>>>
>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>> index 99c8061da55b9..2bdddc725e677 100644
>>> --- a/fs/f2fs/checkpoint.c
>>> +++ b/fs/f2fs/checkpoint.c
>>> @@ -1255,11 +1255,7 @@ static void unblock_operations(struct f2fs_sb_info *sbi)
>>> void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
>>> {
>>> - DEFINE_WAIT(wait);
>>> -
>>> for (;;) {
>>> - prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
>>
>> Wouldn't that case high cpu usage before io end?
>
> This is a critical path to wait for IO completion in checkpoint, which would be
> better to wait for it to avoid long latency to continue filesystem operations.
Yup, in previous implementation, last end_io wakes up checkpoint() waiter, we
didn't waste any time there.
> Moreover, I expect io_schedule_timeout() can mitigate such the CPU overhead and
> actually we don't need to make there-in context switches as well.
Then io_schedule_timeout() in this loop may give CPU time slice to other thread
until scheduler reselect checkpoint(), that would cause longer latency?
>
>>
>>> -
>>> if (!get_pages(sbi, type))
>>> break;
>>> @@ -1271,9 +1267,9 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
>>> FS_CP_META_IO);
>>> else if (type == F2FS_WB_CP_DATA)
>>> f2fs_submit_merged_write(sbi, DATA);
>>> +
>>> io_schedule_timeout(DEFAULT_IO_TIMEOUT);
>>> }
>>> - finish_wait(&sbi->cp_wait, &wait);
>>> }
>>> static void update_ckpt_flags(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>> index c1b676be67b9a..588d2871bbe69 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -383,10 +383,6 @@ static void f2fs_write_end_io(struct bio *bio)
>>> clear_cold_data(page);
>>> end_page_writeback(page);
>>> }
>>> - if (!get_pages(sbi, F2FS_WB_CP_DATA) &&
>>> - wq_has_sleeper(&sbi->cp_wait))
>>> - wake_up(&sbi->cp_wait);
>>> -
>>> bio_put(bio);
>>> }
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index 02811ce15059b..a036539363030 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -1437,7 +1437,6 @@ struct f2fs_sb_info {
>>> struct rw_semaphore cp_rwsem; /* blocking FS operations */
>>> struct rw_semaphore node_write; /* locking node writes */
>>> struct rw_semaphore node_change; /* locking node change */
>>> - wait_queue_head_t cp_wait;
>>> unsigned long last_time[MAX_TIME]; /* to store time in jiffies */
>>> long interval_time[MAX_TIME]; /* to store thresholds */
>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>> index 83bf9a02f83f2..5f4d9abc079d6 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -3540,7 +3540,6 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>> init_rwsem(&sbi->cp_rwsem);
>>> init_rwsem(&sbi->quota_sem);
>>> - init_waitqueue_head(&sbi->cp_wait);
>>> init_sb_info(sbi);
>>> err = init_percpu_info(sbi);
>>>
> .
>
On 08/04, Chao Yu wrote:
> On 2020/8/4 9:04, Jaegeuk Kim wrote:
> > On 08/04, Chao Yu wrote:
> > > On 2020/8/4 1:28, Jaegeuk Kim wrote:
> > > > It doesn't need to wait for checkpoint being completed triggered by end_io.
> > > >
> > > > [ 20.157753] ------------[ cut here ]------------
> > > > [ 20.158393] do not call blocking ops when !TASK_RUNNING; state=2 set at [<0000000096354225>] prepare_to_wait+0xcd/0x430
> > > > [ 20.159858] WARNING: CPU: 1 PID: 1152 at kernel/sched/core.c:7142 __might_sleep+0x149/0x1a0
> > > > ...
> > > > [ 20.176110] __submit_merged_write_cond+0x191/0x310
> > > > [ 20.176739] f2fs_submit_merged_write+0x18/0x20
> > > > [ 20.177323] f2fs_wait_on_all_pages+0x269/0x2d0
> > > > [ 20.177899] ? block_operations+0x980/0x980
> > > > [ 20.178441] ? __kasan_check_read+0x11/0x20
> > > > [ 20.178975] ? finish_wait+0x260/0x260
> > > > [ 20.179488] ? percpu_counter_set+0x147/0x230
> > > > [ 20.180049] do_checkpoint+0x1757/0x2a50
> > > > [ 20.180558] f2fs_write_checkpoint+0x840/0xaf0
> > > > [ 20.181126] f2fs_sync_fs+0x287/0x4a0
> > > >
> > > > Reported-by: Eric Biggers <[email protected]>
> > > > Signed-off-by: Jaegeuk Kim <[email protected]>
> > > > ---
> > > > fs/f2fs/checkpoint.c | 6 +-----
> > > > fs/f2fs/data.c | 4 ----
> > > > fs/f2fs/f2fs.h | 1 -
> > > > fs/f2fs/super.c | 1 -
> > > > 4 files changed, 1 insertion(+), 11 deletions(-)
> > > >
> > > > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > > > index 99c8061da55b9..2bdddc725e677 100644
> > > > --- a/fs/f2fs/checkpoint.c
> > > > +++ b/fs/f2fs/checkpoint.c
> > > > @@ -1255,11 +1255,7 @@ static void unblock_operations(struct f2fs_sb_info *sbi)
> > > > void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
> > > > {
> > > > - DEFINE_WAIT(wait);
> > > > -
> > > > for (;;) {
> > > > - prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
> > >
> > > Wouldn't that case high cpu usage before io end?
> >
> > This is a critical path to wait for IO completion in checkpoint, which would be
> > better to wait for it to avoid long latency to continue filesystem operations.
>
> Yup, in previous implementation, last end_io wakes up checkpoint() waiter, we
> didn't waste any time there.
>
> > Moreover, I expect io_schedule_timeout() can mitigate such the CPU overhead and
> > actually we don't need to make there-in context switches as well.
>
> Then io_schedule_timeout() in this loop may give CPU time slice to other thread
> until scheduler reselect checkpoint(), that would cause longer latency?
Hmm, how about this then?
From 4956afa1cedc019cabf6e8bff7bc48d3bcf7a3f5 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <[email protected]>
Date: Mon, 3 Aug 2020 19:37:12 -0700
Subject: [PATCH] f2fs: prepare a waiter before entering io_schedule
This is to avoid sleep() in the waiter thread.
[ 20.157753] ------------[ cut here ]------------
[ 20.158393] do not call blocking ops when !TASK_RUNNING; state=2 set at [<0000000096354225>] prepare_to_wait+0xcd/0x430
[ 20.159858] WARNING: CPU: 1 PID: 1152 at kernel/sched/core.c:7142 __might_sleep+0x149/0x1a0
...
[ 20.176110] __submit_merged_write_cond+0x191/0x310
[ 20.176739] f2fs_submit_merged_write+0x18/0x20
[ 20.177323] f2fs_wait_on_all_pages+0x269/0x2d0
[ 20.177899] ? block_operations+0x980/0x980
[ 20.178441] ? __kasan_check_read+0x11/0x20
[ 20.178975] ? finish_wait+0x260/0x260
[ 20.179488] ? percpu_counter_set+0x147/0x230
[ 20.180049] do_checkpoint+0x1757/0x2a50
[ 20.180558] f2fs_write_checkpoint+0x840/0xaf0
[ 20.181126] f2fs_sync_fs+0x287/0x4a0
Reported-by: Eric Biggers <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>
---
fs/f2fs/checkpoint.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 99c8061da55b9..ff807e14c8911 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1258,8 +1258,6 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
DEFINE_WAIT(wait);
for (;;) {
- prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
-
if (!get_pages(sbi, type))
break;
@@ -1271,6 +1269,8 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
FS_CP_META_IO);
else if (type == F2FS_WB_CP_DATA)
f2fs_submit_merged_write(sbi, DATA);
+
+ prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
io_schedule_timeout(DEFAULT_IO_TIMEOUT);
}
finish_wait(&sbi->cp_wait, &wait);
--
2.28.0.163.g6104cc2f0b6-goog
On 2020/8/4 10:43, Jaegeuk Kim wrote:
> On 08/04, Chao Yu wrote:
>> On 2020/8/4 9:04, Jaegeuk Kim wrote:
>>> On 08/04, Chao Yu wrote:
>>>> On 2020/8/4 1:28, Jaegeuk Kim wrote:
>>>>> It doesn't need to wait for checkpoint being completed triggered by end_io.
>>>>>
>>>>> [ 20.157753] ------------[ cut here ]------------
>>>>> [ 20.158393] do not call blocking ops when !TASK_RUNNING; state=2 set at [<0000000096354225>] prepare_to_wait+0xcd/0x430
>>>>> [ 20.159858] WARNING: CPU: 1 PID: 1152 at kernel/sched/core.c:7142 __might_sleep+0x149/0x1a0
>>>>> ...
>>>>> [ 20.176110] __submit_merged_write_cond+0x191/0x310
>>>>> [ 20.176739] f2fs_submit_merged_write+0x18/0x20
>>>>> [ 20.177323] f2fs_wait_on_all_pages+0x269/0x2d0
>>>>> [ 20.177899] ? block_operations+0x980/0x980
>>>>> [ 20.178441] ? __kasan_check_read+0x11/0x20
>>>>> [ 20.178975] ? finish_wait+0x260/0x260
>>>>> [ 20.179488] ? percpu_counter_set+0x147/0x230
>>>>> [ 20.180049] do_checkpoint+0x1757/0x2a50
>>>>> [ 20.180558] f2fs_write_checkpoint+0x840/0xaf0
>>>>> [ 20.181126] f2fs_sync_fs+0x287/0x4a0
>>>>>
>>>>> Reported-by: Eric Biggers <[email protected]>
>>>>> Signed-off-by: Jaegeuk Kim <[email protected]>
>>>>> ---
>>>>> fs/f2fs/checkpoint.c | 6 +-----
>>>>> fs/f2fs/data.c | 4 ----
>>>>> fs/f2fs/f2fs.h | 1 -
>>>>> fs/f2fs/super.c | 1 -
>>>>> 4 files changed, 1 insertion(+), 11 deletions(-)
>>>>>
>>>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>>>> index 99c8061da55b9..2bdddc725e677 100644
>>>>> --- a/fs/f2fs/checkpoint.c
>>>>> +++ b/fs/f2fs/checkpoint.c
>>>>> @@ -1255,11 +1255,7 @@ static void unblock_operations(struct f2fs_sb_info *sbi)
>>>>> void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
>>>>> {
>>>>> - DEFINE_WAIT(wait);
>>>>> -
>>>>> for (;;) {
>>>>> - prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
>>>>
>>>> Wouldn't that case high cpu usage before io end?
>>>
>>> This is a critical path to wait for IO completion in checkpoint, which would be
>>> better to wait for it to avoid long latency to continue filesystem operations.
>>
>> Yup, in previous implementation, last end_io wakes up checkpoint() waiter, we
>> didn't waste any time there.
>>
>>> Moreover, I expect io_schedule_timeout() can mitigate such the CPU overhead and
>>> actually we don't need to make there-in context switches as well.
>>
>> Then io_schedule_timeout() in this loop may give CPU time slice to other thread
>> until scheduler reselect checkpoint(), that would cause longer latency?
>
> Hmm, how about this then?
>
>>From 4956afa1cedc019cabf6e8bff7bc48d3bcf7a3f5 Mon Sep 17 00:00:00 2001
> From: Jaegeuk Kim <[email protected]>
> Date: Mon, 3 Aug 2020 19:37:12 -0700
> Subject: [PATCH] f2fs: prepare a waiter before entering io_schedule
>
> This is to avoid sleep() in the waiter thread.
>
> [ 20.157753] ------------[ cut here ]------------
> [ 20.158393] do not call blocking ops when !TASK_RUNNING; state=2 set at [<0000000096354225>] prepare_to_wait+0xcd/0x430
> [ 20.159858] WARNING: CPU: 1 PID: 1152 at kernel/sched/core.c:7142 __might_sleep+0x149/0x1a0
> ...
> [ 20.176110] __submit_merged_write_cond+0x191/0x310
> [ 20.176739] f2fs_submit_merged_write+0x18/0x20
> [ 20.177323] f2fs_wait_on_all_pages+0x269/0x2d0
> [ 20.177899] ? block_operations+0x980/0x980
> [ 20.178441] ? __kasan_check_read+0x11/0x20
> [ 20.178975] ? finish_wait+0x260/0x260
> [ 20.179488] ? percpu_counter_set+0x147/0x230
> [ 20.180049] do_checkpoint+0x1757/0x2a50
> [ 20.180558] f2fs_write_checkpoint+0x840/0xaf0
> [ 20.181126] f2fs_sync_fs+0x287/0x4a0
>
> Reported-by: Eric Biggers <[email protected]>
> Signed-off-by: Jaegeuk Kim <[email protected]>
Better,
Reviewed-by: Chao Yu <[email protected]>
Thanks,
> ---
> fs/f2fs/checkpoint.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 99c8061da55b9..ff807e14c8911 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -1258,8 +1258,6 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
> DEFINE_WAIT(wait);
>
> for (;;) {
> - prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
> -
> if (!get_pages(sbi, type))
> break;
>
> @@ -1271,6 +1269,8 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
> FS_CP_META_IO);
> else if (type == F2FS_WB_CP_DATA)
> f2fs_submit_merged_write(sbi, DATA);
> +
> + prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
> io_schedule_timeout(DEFAULT_IO_TIMEOUT);
> }
> finish_wait(&sbi->cp_wait, &wait);
>