linux-kernel - Re: [f2fs-dev] [PATCH v2] f2fs: introduce periodic iostat io latency traces

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Date:   Sat, 14 Aug 2021 21:27:47 -0700
From:   Daeho Jeong <daeho43@...il.com>
To:     Chao Yu <chao@...nel.org>
Cc:     Jaegeuk Kim <jaegeuk@...nel.org>, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH v2] f2fs: introduce periodic iostat io latency traces

Actually, I was working on it, after Chao pointed it out. :)
Merging them into F2FS_IOST and separating it from other files looks better.

On Fri, Aug 13, 2021 at 7:06 PM Chao Yu <chao@...nel.org> wrote:
>
> On 2021/8/14 2:56, Jaegeuk Kim wrote:
> > On 08/13, Chao Yu wrote:
> >> On 2021/8/13 4:52, Jaegeuk Kim wrote:
> >>> On 08/11, Chao Yu wrote:
> >>>> Hi Daeho,
> >>>>
> >>>> On 2021/8/4 6:55, Daeho Jeong wrote:
> >>>>> From: Daeho Jeong <daehojeong@...gle.com>
> >>>>>
> >>>>> Whenever we notice some sluggish issues on our machines, we are always
> >>>>> curious about how well all types of I/O in the f2fs filesystem are
> >>>>> handled. But, it's hard to get this kind of real data. First of all,
> >>>>> we need to reproduce the issue while turning on the profiling tool like
> >>>>> blktrace, but the issue doesn't happen again easily. Second, with the
> >>>>> intervention of any tools, the overall timing of the issue will be
> >>>>> slightly changed and it sometimes makes us hard to figure it out.
> >>>>>
> >>>>> So, I added F2FS_IOSTAT_IO_LATENCY config option to support printing out
> >>>>> IO latency statistics tracepoint events which are minimal things to
> >>>>> understand filesystem's I/O related behaviors. With "iostat_enable" sysfs
> >>>>> node on, we can get this statistics info in a periodic way and it
> >>>>> would cause the least overhead.
> >>>>>
> >>>>> [samples]
> >>>>>     f2fs_ckpt-254:1-507     [003] ....  2842.439683: f2fs_iostat_latency:
> >>>>> dev = (254,11), iotype [peak lat.(ms)/avg lat.(ms)/count],
> >>>>> rd_data [136/1/801], rd_node [136/1/1704], rd_meta [4/2/4],
> >>>>> wr_sync_data [164/16/3331], wr_sync_node [152/3/648],
> >>>>> wr_sync_meta [160/2/4243], wr_async_data [24/13/15],
> >>>>> wr_async_node [0/0/0], wr_async_meta [0/0/0]
> >>>>>
> >>>>>     f2fs_ckpt-254:1-507     [002] ....  2845.450514: f2fs_iostat_latency:
> >>>>> dev = (254,11), iotype [peak lat.(ms)/avg lat.(ms)/count],
> >>>>> rd_data [60/3/456], rd_node [60/3/1258], rd_meta [0/0/1],
> >>>>> wr_sync_data [120/12/2285], wr_sync_node [88/5/428],
> >>>>> wr_sync_meta [52/6/2990], wr_async_data [4/1/3],
> >>>>> wr_async_node [0/0/0], wr_async_meta [0/0/0]
> >>>>>
> >>>>> Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> >>>>>
> >>>>> ---
> >>>>> v2: clean up with wrappers and fix a build breakage reported by
> >>>>>        kernel test robot <lkp@...el.com>
> >>>>> ---
> >>>>>     fs/f2fs/Kconfig             |   9 +++
> >>>>
> >>>> I try to apply this patch in my local dev branch, but it failed due to
> >>>> conflicting with below commit, it needs to rebase this patch to last dev
> >>>> branch.
> >>>
> >>> I applied this in dev branch. Could you please check?
> >>
> >> Yeah, I see.
> >>
> >>>>> +config F2FS_IOSTAT_IO_LATENCY
> >>>>> + bool "F2FS IO statistics IO latency information"
> >>>>> + depends on F2FS_FS
> >>>>> + default n
> >>>>> + help
> >>>>> +   Support printing out periodic IO latency statistics tracepoint
> >>>>> +   events. With this, you have to turn on "iostat_enable" sysfs
> >>>>> +   node to print this out.
> >>>>
> >>>> This functionality looks independent, how about introuducing iostat.h
> >>>> and iostat.c (not sure, maybe trace.[hc])to include newly added structure
> >>>> and functions for dispersive codes cleanup.
> >>
> >> Thoughts? this also can avoid using CONFIG_F2FS_IOSTAT_IO_LATENCY in many places.
> >
> > It seems there's somewhat dependency with iostat which is done by default.
> > How about adding this by default as well in the existing iostat, and then
> > covering all together by F2FS_IOSTAT?
>
> Agreed.
>
> Any thoughts about using separated files to maintain these independent functionality
> codes? like we did in trace.[hc] previously.
>
> Thanks,
>
> >
> >>
> >> Thanks,