Messages in this thread | | | Subject | Re: [f2fs-dev] [PATCH] f2fs: remove a waiter for checkpoint completion | From | Chao Yu <> | Date | Tue, 4 Aug 2020 11:00:01 +0800 |
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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 <ebiggers@kernel.org> >>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> >>>>> --- >>>>> 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 <jaegeuk@kernel.org> > 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 <ebiggers@kernel.org> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Better,
Reviewed-by: Chao Yu <yuchao0@huawei.com>
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); >
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