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

[Chao Yu]

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@xxxxxxxxxx>
> > >
> > > 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@xxxxxxxxxx>
> > >
> > > ---
> > > v2: clean up with wrappers and fix a build breakage reported by
> > >       kernel test robot <lkp@xxxxxxxxx>
> > > ---
> > >    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.

Thanks,