linux-kernel - Re: [PATCH] nvme: add cond_resched() to nvme_complete

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Message-ID: <ZFLxXjiQUPl+tV8L@kbusch-mbp.dhcp.thefacebook.com>
Date:   Wed, 3 May 2023 17:42:22 -0600
From:   Keith Busch <kbusch@...nel.org>
To:     jiweisun126@....com
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        axboe@...com, hch@....de, sagi@...mberg.me, ahuang12@...ovo.com,
        sunjw10@...ovo.com
Subject: Re: [PATCH] nvme: add cond_resched() to nvme_complete_batch()

On Wed, May 03, 2023 at 10:28:53AM -0600, Keith Busch wrote:
> On Tue, May 02, 2023 at 08:54:12PM +0800, jiweisun126@....com wrote:
> > According to the above two logs, we can know the nvme_irq() cost too much
> > time, in the above case, about 4.8 second. And we can also know that the
> > main bottlenecks is in the competition for the spin lock pool->lock.
> 
> I have a fix that makes pool->lock critical section much shorter and constant
> time. It was staged in mm tree for months, but mysteriously it's missing...

Well this is certainly odd: the commit I'm referring to is in Linus' log, but
the file it modified is not updated. What kind of 'git' madness is this??

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a4de12a032fa6d0670aa0bb43a2bf9f812680d0f

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/mm/dmapool.c