From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>,
kbusch@kernel.org, linux-block@vger.kernel.org
Subject: Re: [PATCH] blk-mq: always take a queue reference in blk_mq_submit_bio
Date: Fri, 22 May 2026 10:56:49 +0200 [thread overview]
Message-ID: <20260522085649.GB6702@lst.de> (raw)
In-Reply-To: <89c94510-abb6-485c-87c4-73364c8f6914@kernel.dk>
On Thu, May 21, 2026 at 09:12:05AM -0600, Jens Axboe wrote:
> This is about a 5% regression in peak performance, fwiw. I'm all for
> eliminating this issue, but this kind of big hammer approach is pretty
> crap in terms of adding overhead to the IO path. Maybe we just cover
> blocking split bio case, and look into doing a proper fix for 7.2 that
> isn't such a massive regression?
Well, that assumes we have an idea how to fix it? So much overhead for a
simple per-cpu counters sounds really weird to start with. We'd need to
look at the numbers from your setup as I don't have anything equivalent.
I'd honestly still prefer to get this right first over optimizations
either way.
prev parent reply other threads:[~2026-05-22 8:56 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-20 8:49 [PATCH] blk-mq: always take a queue reference in blk_mq_submit_bio Christoph Hellwig
2026-05-20 14:59 ` Keith Busch
2026-05-21 15:12 ` Jens Axboe
2026-05-22 8:56 ` Christoph Hellwig [this message]
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