Messages in this thread | | | Subject | Re: [f2fs-dev] [PATCH] f2fs: remove a waiter for checkpoint completion | From | Chao Yu <> | Date | Tue, 4 Aug 2020 09:17:16 +0800 |
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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?
> >> >>> - >>> 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); >>> > . >
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