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

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Date:	Wed, 5 Mar 2014 12:23:53 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Fengguang Wu <fengguang.wu@...el.com>
Cc:	Kent Overstreet <kmo@...erainc.com>,
	LKML <linux-kernel@...r.kernel.org>, lkp@...org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [blk-lib] 6a0608544e5: fileio -77.4% max latency, -5.7%
 throughput

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?

> 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 ;)

Cheers,

Dave.

-- 
Dave Chinner
david@...morbit.com
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