Re: [blk-lib] 6a0608544e5: fileio -77.4% max latency, -5.7% throughput

Fengguang Wu
2014-03-05T02:08:09Z

On Wed, Mar 05, 2014 at 12:23:53PM +1100, Dave Chinner wrote:
> On Wed, Mar 05, 2014 at 09:16:45AM +0800, Fengguang Wu wrote:
> > On Tue, Mar 04, 2014 at 01:52:25PM -0800, Kent Overstreet wrote:
> > > On Tue, Mar 04, 2014 at 09:21:30PM +0800, Fengguang Wu wrote:
> > > > Hi Kent,
> > > >
> > > > FYI, we noticed the below changes on
> > > >
> > > > git://evilpiepirate.org/~kent/linux-bcache.git for-jens
> > > > commit 6a0608544e5672bd9a044c285119547eae41abe5 ("blk-lib.c: generic_make_request() handles large bios now")
> > > >
> > > > test case: snb-drag/sysbench/fileio/600s-100%-1HDD-ext4-64G-1024-seqrewr-sync
> >
> > snb-drag is the test machine, it's a SNB desktop.
> >
> > The test command is
> >
> > mkfs -t ext4 -q /dev/sda2
> > mount -t ext4 /dev/sda2 /fs/sda2
> > cd /fs/sda2
> >
> > for i in $(seq 0 1023)
> > do
> > fallocate -l 67108864 test_file.$i
> > done
> >
> > sysbench --test=fileio --max-requests=0 --num-threads=4 --max-time=600 --file-test-mode=seqrewr --file-total-size=68719476736 --file-io-mode=sync --file-num=1024 run
> >
> >
> > > I'm trying to figure out how to parse this and the graphs - where do I find the
> > > test? And is there anything you can point me to for the graphs, or is that
> > > output from that test?
> > >
> > > >
> > > > 11541d5f5b7002b 6a0608544e5672bd9a044c285
> > > > --------------- -------------------------
> > > > 1885 ~60% -77.4% 426 ~ 7% TOTAL fileio.request_latency_max_ms
> >
> > The ~XX% numbers are stddev percent.
> > The [+-]XX% is change percent.
>
> Can you put this in as column headers so that people don't have to
> this every time they see a report from you?

Good idea!

> > The below graph shows all samples collected during the bisect
> >
> > [*] bisect-good
> > [O] bisect-bad
> >
> > In which you can see the stableness of the change and bisect.
>
> Oh, so that's what the graphs contain. :/
>
> Again - perhaps you should include this information with the graphs
> rather than just dumping unlabelled data on people ;)

Yeah sure. I'll follow your nice suggestions!

Thanks,
Fengguang