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Date:   Wed, 19 Apr 2023 16:15:47 +0300
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Subject: Re: [RFC v1 0/1] nvme testsuite runtime optimization
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To:     Daniel Wagner <dwagner@suse.de>
Cc:     Chaitanya Kulkarni <chaitanyak@nvidia.com>,
        "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        Shin'ichiro Kawasaki <shinichiro@fastmail.com>
References: <20230419085643.25714-1-dwagner@suse.de>
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From:   Sagi Grimberg <sagi@grimberg.me>
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>>>> 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.
> 
> first run was with loop, second one with rdma:
> 
> nvme/002 (create many subsystems and test discovery)         [not run]
>      runtime  82.089s  ...
>      nvme_trtype=rdma is not supported in this test
> 
> nvme/016 (create/delete many NVMeOF block device-backed ns and test discovery) [not run]
>      runtime  39.948s  ...
>      nvme_trtype=rdma is not supported in this test
> nvme/017 (create/delete many file-ns and test discovery)     [not run]
>      runtime  40.237s  ...
> 
> nvme/047 (test different queue types for fabric transports)  [passed]
>      runtime    ...  13.580s
> nvme/048 (Test queue count changes on reconnect)             [passed]
>      runtime    ...  6.287s
> 
> 82 + 40 + 40 - 14 - 6 = 142. So loop runs additional tests. Hmm, though my
> optimization didn't work there...

How come loop is 4m+ while the others are 2m+ when before all
were the same timeframe more or less?

> 
>>> 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?
> 
> No idea, it just the existing hard coded values. I guess it might be from
> efa06fcf3c83 ("loop: test partition scanning") which was the first real test
> case (according the logs).

Was asking Chaitanya why is 1G considered sufficient vs. other sizes?
Why not 10G? Why not 100M?