linux-kernel - Re: [PATCH] blk-mq: allow hardware queue to get more tag while sharing a tag set

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Message-ID: <b4603b71-4306-4542-e4fb-bf30133f89a8@acm.org>
Date:   Thu, 5 Aug 2021 19:43:11 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     "yukuai (C)" <yukuai3@...wei.com>, axboe@...nel.dk,
        ming.lei@...hat.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com
Subject: Re: [PATCH] blk-mq: allow hardware queue to get more tag while
 sharing a tag set

On 8/5/21 6:50 PM, yukuai (C) wrote:
> After applying this configuration, the number of null_blk in my
> machine is about 650k(330k before). Is this still too low?

That seems low to me. If I run the attached script on a six year old
desktop with an eight core i7-4790 CPU it reports a little more than 5
million IOPS. Has kernel debugging perhaps been enabled in the kernel on
the test setup? Or is the system perhaps slowed down by security
mitigations?

> By the way, there are no performance degradation.

Please wait with drawing a conclusion until you can run a workload on
your setup of several million IOPS.

Thanks,

Bart.

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