linux-kernel - Re: [LKP] [block] 34b48db66e0: +3291.6% iostat.sde.wrqm/s

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Message-ID: <54C1647A.3090804@fb.com>
Date:	Thu, 22 Jan 2015 13:58:34 -0700
From:	Jens Axboe <axboe@...com>
To:	Jeff Moyer <jmoyer@...hat.com>
CC:	Huang Ying <ying.huang@...el.com>, Christoph Hellwig <hch@....de>,
	LKML <linux-kernel@...r.kernel.org>, LKP ML <lkp@...org>
Subject: Re: [LKP] [block] 34b48db66e0: +3291.6% iostat.sde.wrqm/s

On 01/22/2015 01:49 PM, Jeff Moyer wrote:
> Jens Axboe <axboe@...com> writes:
> 
>>> Agreed on all above, but are the actual benchmark numbers included
>>> somewhere in all this mess?  I'd like to see if the benchmark numbers
>>> improved first, before digging into the guts of which functions are
>>> called more or which stats changed.
>>
>> I deleted the original email, but the latter tables had drive throughput
>> rates and it looked higher for the ones I checked on the newer kernel.
>> Which the above math would indicate as well, multiplying reqs-per-sec
>> and req-size.
> 
> Looking back at the original[1], I think I see the throughput numbers for
> iozone.  The part that confused me was that each table mixes different
> types of data.  I'd much prefer if different data were put in different
> tables, along with column headers that stated what was being reported
> and the units for the measurements.
> 
> Anyway, I find the increased service time troubling, especially this
> one:
> 
> testbox/testcase/testparams: ivb44/fsmark/performance-1x-1t-1HDD-xfs-4M-60G-NoSync
> 
>        544 ?  0%   +1268.9%       7460 ?  0%  iostat.sda.w_await
>        544 ?  0%   +1268.5%       7457 ?  0%  iostat.sda.await
> 
> I'll add this to my queue of things to look into.

>From that same table:

      1009 ±  0%   +1255.7%      13682 ±  0%  iostat.sda.avgrq-sz

the average request size has gone up equally. This is clearly a streamed
oriented benchmark, if the IOs get that big.


-- 
Jens Axboe

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