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Date: Tue, 13 Oct 2015 10:03:08 -0700
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: He YunLei <heyunlei@...wei.com>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 2/3] f2fs: add a tracepoint for background gc
On Sat, Oct 10, 2015 at 03:08:26PM +0800, He YunLei wrote:
> On 2015/10/6 6:43, Jaegeuk Kim wrote:
> > This patch introduces a tracepoint to monitor background gc behaviors.
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > ---
> > fs/f2fs/gc.c | 3 +++
> > include/trace/events/f2fs.h | 28 ++++++++++++++++++++++++++++
> > 2 files changed, 31 insertions(+)
> >
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index e627c19..e7cec86 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -77,6 +77,9 @@ static int gc_thread_func(void *data)
> >
> > stat_inc_bggc_count(sbi);
> >
> > + trace_f2fs_background_gc(sbi->sb, wait_ms,
> > + prefree_segments(sbi), free_segments(sbi));
> > +
> > /* if return value is not zero, no victim was selected */
> > if (f2fs_gc(sbi, test_opt(sbi, FORCE_FG_GC)))
> > wait_ms = gc_th->no_gc_sleep_time;
> > diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
> > index 6aa63d9..7de751d 100644
> > --- a/include/trace/events/f2fs.h
> > +++ b/include/trace/events/f2fs.h
> > @@ -514,6 +514,34 @@ TRACE_EVENT(f2fs_map_blocks,
> > __entry->ret)
> > );
> >
> > +TRACE_EVENT(f2fs_background_gc,
> > +
> > + TP_PROTO(struct super_block *sb, long wait_ms,
> > + unsigned int prefree, unsigned int free),
> > +
> > + TP_ARGS(sb, wait_ms, prefree, free),
> > +
> > + TP_STRUCT__entry(
> > + __field(dev_t, dev)
> > + __field(long, wait_ms)
> > + __field(unsigned int, prefree)
> > + __field(unsigned int, free)
> > + ),
> > +
> > + TP_fast_assign(
> > + __entry->dev = sb->s_dev;
> > + __entry->wait_ms = wait_ms;
> > + __entry->prefree = prefree;
> > + __entry->free = free;
> > + ),
> > +
> > + TP_printk("dev = (%d,%d), wait_ms = %ld, prefree = %u, free = %u",
> > + show_dev(__entry),
> > + __entry->wait_ms,
> > + __entry->prefree,
> > + __entry->free)
> > +);
> > +
> hi,
> I open f2fs_background_gc and f2fs_get_victim trace points, first, the partition has no dirty segment, so no victim is
> selected, wait_ms is equal to 300s.
>
> f2fs_gc-8:33-2827 [001] .... 5014.608396: f2fs_background_gc: dev = (8,33), wait_ms = 300000, prefree = 0, free = 73
> f2fs_gc-8:33-2827 [000] .... 5314.793436: f2fs_background_gc: dev = (8,33), wait_ms = 300000, prefree = 0, free = 73
>
> then I made the partition satisfied the condition of has_enough_invalid_blocks, gc can get a victim and do garbage collection, wait_ms = 30s
>
> f2fs_gc-8:33-2827 [001] .... 5614.978486: f2fs_background_gc: dev = (8,33), wait_ms = 30000, prefree = 0, free = 54
> f2fs_gc-8:33-2827 [001] .... 5614.978538: f2fs_get_victim: dev = (8,33), type = No TYPE, policy = (Background GC, LFS-mode, Cost-Benefit), victim = 441 ofs_unit = 1, pre_victim_secno = -1, prefree = 0, free = 54
> f2fs_gc-8:33-2827 [000] .... 5644.996989: f2fs_background_gc: dev = (8,33), wait_ms = 30000, prefree = 0, free = 54
> f2fs_gc-8:33-2827 [000] .... 5644.997027: f2fs_get_victim: dev = (8,33), type = No TYPE, policy = (Background GC, LFS-mode, Cost-Benefit), victim = 97 ofs_unit = 1, pre_victim_secno = -1, prefree = 0, free = 54
>
> when there no dirty segments left, I think wait_ms could turn back to 300s
>
> f2fs_gc-8:33-2827 [000] .... 6305.596205: f2fs_background_gc: dev = (8,33), wait_ms = 30000, prefree = 1, free = 64
> f2fs_gc-8:33-2827 [001] .... 6605.781281: f2fs_background_gc: dev = (8,33), wait_ms = 30000, prefree = 0, free = 65
> f2fs_gc-8:33-2827 [000] .... 6905.966301: f2fs_background_gc: dev = (8,33), wait_ms = 30000, prefree = 0, free = 65
> f2fs_gc-8:33-2827 [001] .... 7206.151344: f2fs_background_gc: dev = (8,33), wait_ms = 30000, prefree = 0, free = 65
>
> here, background gc triggers every 300s, but wait_ms is still 30s, I don't know why?
Oh, it's due to the tracepoint timing.
In gc_thread_func(),
do {
wait with wait_ms = 300s
decrease_sleep_time(&wait_ms); -> wait_ms = 30s
tracepoint with wait_ms = 30s
after f2fs_gc() call, wait_ms becomes 300s again.
}
So, this patch should fix that.
>From 84e4214f0868ae77771837d0ed4cc6eff10738ba Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@...nel.org>
Date: Tue, 13 Oct 2015 10:00:53 -0700
Subject: [PATCH] f2fs: relocate the tracepoint for background_gc
Once f2fs_gc is done, wait_ms is changed once more.
So, its tracepoint would be located after it.
Reported-by: He YunLei <heyunlei@...wei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
fs/f2fs/gc.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index af7c24c..fedbf67 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -77,13 +77,13 @@ static int gc_thread_func(void *data)
stat_inc_bggc_count(sbi);
- trace_f2fs_background_gc(sbi->sb, wait_ms,
- prefree_segments(sbi), free_segments(sbi));
-
/* if return value is not zero, no victim was selected */
if (f2fs_gc(sbi, test_opt(sbi, FORCE_FG_GC)))
wait_ms = gc_th->no_gc_sleep_time;
+ trace_f2fs_background_gc(sbi->sb, wait_ms,
+ prefree_segments(sbi), free_segments(sbi));
+
/* balancing f2fs's metadata periodically */
f2fs_balance_fs_bg(sbi);
--
2.1.1
--
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