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Date:   Fri, 11 Mar 2022 22:41:56 +0100
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Subject: Re: [PATCH] block: check more requests for multiple_queues in
 blk_attempt_plug_merge
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To:     Song Liu <song@kernel.org>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-raid@vger.kernel.org, stable@vger.kernel.org,
        Larkin Lowrey <llowrey@nuclearwinter.com>,
        Wilson Jonathan <i400sjon@gmail.com>,
        Roger Heflin <rogerheflin@gmail.com>
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From:   Paul Menzel <pmenzel@molgen.mpg.de>
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Dear Song,


Am 11.03.22 um 17:59 schrieb Song Liu:

> On Fri, Mar 11, 2022 at 6:16 AM Jens Axboe <axboe@kernel.dk> wrote:
>>
>> On 3/10/22 5:07 PM, Jens Axboe wrote:
>>> In any case, just doing larger reads would likely help quite a bit, but
>>> would still be nice to get to the bottom of why we're not seeing the
>>> level of merging we expect.
>>
>> Song, can you try this one? It'll do the dispatch in a somewhat saner
>> fashion, bundling identical queues. And we'll keep iterating the plug
>> list for a merge if we have multiple disks, until we've seen a queue
>> match and checked.
> 
> This one works great! We are seeing 99% read request merge and
> 500kB+ average read size. The original patch in this thread only got
> 88% and 34kB for these two metrics.

Nice. I am curious, how these metrics can be obtained?

[…]


Kind regards,

Paul