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

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Message-ID: <x497fwe8qwo.fsf@segfault.boston.devel.redhat.com>
Date:	Thu, 22 Jan 2015 16:08:23 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Jens Axboe <axboe@...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

Jens Axboe <axboe@...com> writes:

> 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.

Hmm, ok, I'll buy that.  However, I am surprised that the relationship
between i/o size and service time is 1:1 here...

Thanks!
Jeff
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