linux-kernel - Re: [PATCH -next RFC v3 0/8] improve tag allocation under heavy load

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Message-ID: <937972f1-5718-0409-c849-37d757950e14@huawei.com>
Date:   Mon, 25 Apr 2022 21:42:01 +0800
From:   "yukuai (C)" <yukuai3@...wei.com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        <axboe@...nel.dk>, <bvanassche@....org>,
        <andriy.shevchenko@...ux.intel.com>, <john.garry@...wei.com>,
        <ming.lei@...hat.com>, <qiulaibin@...wei.com>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <yi.zhang@...wei.com>
Subject: Re: [PATCH -next RFC v3 0/8] improve tag allocation under heavy load

在 2022/04/25 19:20, Damien Le Moal 写道:
> On 4/25/22 16:28, yukuai (C) wrote:
>> 在 2022/04/25 15:06, Damien Le Moal 写道:
>>
>>>>> By the way, did you check that doing something like:
>>>>>
>>>>> echo 2048 > /sys/block/sdX/queue/nr_requests
>>>>>
>>>>> improves performance for your high number of jobs test case ?
>>>>
>>>> Yes, performance will not degrade when numjobs is not greater than 256
>>>> in this case.
>>>
>>> That is my thinking as well. I am asking if did check that (did you run it ?).
>>
>> Hi,
>>
>> I'm sure I ran it with 256 jobs before.
>>
>> However, I didn't run it with 512 jobs. And following is the result I
>> just tested:
> 
> What was nr_requests ? The default 64 ?
> If you increase that number, do you see better throughput/more requests
> being sequential ?

Sorry if I didn't explain this clearly.

If nr_requests is 64, numjobs is 512, the ratio of sequential is about
20%. If nr_requests is 2048, numjobs is 512, the ratio is 49.1%.

Then yes, increase nr_requests can improve performance in the test case.

> 
> 
>>
>> ratio of sequential io: 49.1%
>>
>> Read|Write seek
>>
>> cnt 99338, zero cnt 48753
>>
>>       >=(KB) .. <(KB)     : count       ratio |distribution
>>                |
>>            0 .. 1         : 48753       49.1%
>> |########################################|
>>            1 .. 2         : 0            0.0% |
>>                |
>>            2 .. 4         : 0            0.0% |
>>                |
>>            4 .. 8         : 0            0.0% |
>>                |
>>            8 .. 16        : 0            0.0% |
>>                |
>>           16 .. 32        : 0            0.0% |
>>                |
>>           32 .. 64        : 0            0.0% |
>>                |
>>           64 .. 128       : 4975         5.0% |#####
>>                |
>>          128 .. 256       : 4439         4.5% |####
>>                |
>>          256 .. 512       : 2615         2.6% |###
>>                |
>>          512 .. 1024      : 967          1.0% |#
>>                |
>>         1024 .. 2048      : 213          0.2% |#
>>                |
>>         2048 .. 4096      : 375          0.4% |#
>>                |
>>         4096 .. 8192      : 723          0.7% |#
>>                |
>>         8192 .. 16384     : 1436         1.4% |##
>>                |
>>        16384 .. 32768     : 2626         2.6% |###
>>                |
>>        32768 .. 65536     : 4197         4.2% |####
>>                |
>>        65536 .. 131072    : 6431         6.5% |######
>>                |
>>       131072 .. 262144    : 7590         7.6% |#######
>>                |
>>       262144 .. 524288    : 6433         6.5% |######
>>                |
>>       524288 .. 1048576   : 4583         4.6% |####
>>                |
>>      1048576 .. 2097152   : 2237         2.3% |##
>>                |
>>      2097152 .. 4194304   : 489          0.5% |#
>>                |
>>      4194304 .. 8388608   : 83           0.1% |#
>>                |
>>      8388608 .. 16777216  : 36           0.0% |#
>>                |
>>     16777216 .. 33554432  : 0            0.0% |
>>                |
>>     33554432 .. 67108864  : 0            0.0% |
>>                |
>>     67108864 .. 134217728 : 137          0.1% |#
>>                |
> 
>