linux-kernel - Re: [RFC v1 0/1] nvme testsuite runtime optimization

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Date:   Wed, 19 Apr 2023 12:50:10 +0300
From:   Sagi Grimberg <sagi@...mberg.me>
To:     Chaitanya Kulkarni <chaitanyak@...dia.com>,
        Daniel Wagner <dwagner@...e.de>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        Shin'ichiro Kawasaki <shinichiro@...tmail.com>
Subject: Re: [RFC v1 0/1] nvme testsuite runtime optimization


>> While testing the fc transport I got a bit tired of wait for the I/O jobs to
>> finish. Thus here some runtime optimization.
>>
>> With a small/slow VM I got following values:
>>
>> with 'optimizations'
>>     loop:
>>       real    4m43.981s
>>       user    0m17.754s
>>       sys     2m6.249s

How come loop is doubling the time with this patch?
ratio is not the same before and after.

>>
>>     rdma:
>>       real    2m35.160s
>>       user    0m6.264s
>>       sys     0m56.230s
>>
>>     tcp:
>>       real    2m30.391s
>>       user    0m5.770s
>>       sys     0m46.007s
>>
>>     fc:
>>       real    2m19.738s
>>       user    0m6.012s
>>       sys     0m42.201s
>>
>> base:
>>     loop:
>>       real    7m35.061s
>>       user    0m23.493s
>>       sys     2m54.866s
>>
>>     rdma:
>>       real    8m29.347s
>>       user    0m13.078s
>>       sys     1m53.158s
>>
>>     tcp:
>>       real    8m11.357s
>>       user    0m13.033s
>>       sys     2m43.156s
>>
>>     fc:
>>       real    5m46.615s
>>       user    0m12.819s
>>       sys     1m46.338s
>>
>>
> 
> Those jobs are meant to be run for at least 1G to establish
> confidence on the data set and the system under test since SSDs
> are in TBs nowadays and we don't even get anywhere close to that,
> with your suggestion we are going even lower ...

Where does the 1G boundary coming from?

> we cannot change the dataset size for slow VMs, instead add
> a command line argument and pass it to tests e.g.
> nvme_verification_size=XXX similar to nvme_trtype but don't change
> the default values which we have been testing for years now
> 
> Testing is supposed to be time consuming especially verification jobs..

I like the idea, but I think it may need to be the other way around.
Have shortest possible runs by default.