* [PATCH] f2fs: avoid hungtask problem caused by f2fs_balance_fs
@ 2016-02-26 7:13 Yunlei He
2016-02-26 15:54 ` Chao Yu
0 siblings, 1 reply; 2+ messages in thread
From: Yunlei He @ 2016-02-26 7:13 UTC (permalink / raw)
To: chao2.yu, jaegeuk, linux-f2fs-devel
I came across a hungtask problem as below:
INFO: task 962 blocked for more than 120 s.
Call trace:
[<ffffffc000085a24>] __switch_to+0x74/0x8c
[<ffffffc000dd1434>] __schedule+0x3b4/0x8f4
[<ffffffc000dd1998>] schedule+0x24/0x68
[<ffffffc000dd1e80>] schedule_preempt_disabled+0x10/0x24
[<ffffffc000dd04b4>] __mutex_lock_slowpath+0x154/0x26c
[<ffffffc000dd0610>] mutex_lock+0x44/0x64
[<ffffffc0003471d0>] f2fs_balance_fs+0x78/0x94
[<ffffffc00032ca00>] f2fs_create+0x30/0x1d4
[<ffffffc0001a5e40>] vfs_create+0xc8/0xf8
[<ffffffc0001a7a34>] do_last.isra.43+0x608/0xc44
[<ffffffc0001a8118>] path_openat.isra.44+0xa8/0x4b0
[<ffffffc0001a92dc>] do_filp_open+0x2c/0x98
[<ffffffc000198da0>] do_sys_open+0x104/0x1c8
[<ffffffc000198e98>] SyS_openat+0xc/0x18
Besides, there are also lots of other operations were blocked
by gc_mutex like here.
The comments said we should do GC or end up with checkpoint, if there
are so many dirty dir/node pages without enough free segments. But should
all theads wait for gc if the condition is not satisfied? Maybe if someone
is gcing, they can by pass it.
Signed-off-by: Yunlei He <heyunlei@huawei.com>
---
fs/f2fs/segment.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 6f16b39..48ce7ab 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -345,8 +345,8 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
* We should do GC or end up with checkpoint, if there are so many dirty
* dir/node pages without enough free segments.
*/
- if (has_not_enough_free_secs(sbi, 0)) {
- mutex_lock(&sbi->gc_mutex);
+ if (has_not_enough_free_secs(sbi, 0) &&
+ mutex_trylock(&sbi->gc_mutex)) {
f2fs_gc(sbi, false);
}
}
--
1.9.1
------------------------------------------------------------------------------
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^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] f2fs: avoid hungtask problem caused by f2fs_balance_fs
2016-02-26 7:13 [PATCH] f2fs: avoid hungtask problem caused by f2fs_balance_fs Yunlei He
@ 2016-02-26 15:54 ` Chao Yu
0 siblings, 0 replies; 2+ messages in thread
From: Chao Yu @ 2016-02-26 15:54 UTC (permalink / raw)
To: Yunlei He, chao2.yu, jaegeuk, linux-f2fs-devel
Hi Yunlei,
On 2016/2/26 15:13, Yunlei He wrote:
> I came across a hungtask problem as below:
>
> INFO: task 962 blocked for more than 120 s.
>
> Call trace:
> [<ffffffc000085a24>] __switch_to+0x74/0x8c
> [<ffffffc000dd1434>] __schedule+0x3b4/0x8f4
> [<ffffffc000dd1998>] schedule+0x24/0x68
> [<ffffffc000dd1e80>] schedule_preempt_disabled+0x10/0x24
> [<ffffffc000dd04b4>] __mutex_lock_slowpath+0x154/0x26c
> [<ffffffc000dd0610>] mutex_lock+0x44/0x64
> [<ffffffc0003471d0>] f2fs_balance_fs+0x78/0x94
> [<ffffffc00032ca00>] f2fs_create+0x30/0x1d4
> [<ffffffc0001a5e40>] vfs_create+0xc8/0xf8
> [<ffffffc0001a7a34>] do_last.isra.43+0x608/0xc44
> [<ffffffc0001a8118>] path_openat.isra.44+0xa8/0x4b0
> [<ffffffc0001a92dc>] do_filp_open+0x2c/0x98
> [<ffffffc000198da0>] do_sys_open+0x104/0x1c8
> [<ffffffc000198e98>] SyS_openat+0xc/0x18
>
> Besides, there are also lots of other operations were blocked
> by gc_mutex like here.
>
> The comments said we should do GC or end up with checkpoint, if there
> are so many dirty dir/node pages without enough free segments. But should
> all theads wait for gc if the condition is not satisfied? Maybe if someone
> is gcing, they can by pass it.
I don't think so, once there is one thread goes into GC flow, if we don't block
all other foreground gc threads here, these concurrent threads may generate more
dirty node/dentry pages, which can easily lead sync_node_pages in GC or
checkpoint runs out of free sections.
Thanks,
>
> Signed-off-by: Yunlei He <heyunlei@huawei.com>
> ---
> fs/f2fs/segment.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 6f16b39..48ce7ab 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -345,8 +345,8 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
> * We should do GC or end up with checkpoint, if there are so many dirty
> * dir/node pages without enough free segments.
> */
> - if (has_not_enough_free_secs(sbi, 0)) {
> - mutex_lock(&sbi->gc_mutex);
> + if (has_not_enough_free_secs(sbi, 0) &&
> + mutex_trylock(&sbi->gc_mutex)) {
> f2fs_gc(sbi, false);
> }
> }
>
------------------------------------------------------------------------------
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2016-02-26 15:54 ` Chao Yu
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