From: Christoph Hellwig <hch@infradead.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: [PATCH] block: use flags instead of bit fields for blkdev_dio
Date: Fri, 15 Oct 2021 21:30:48 -0700 [thread overview]
Message-ID: <YWpVeBfUt3zoafD4@infradead.org> (raw)
In-Reply-To: <4b427811-106d-53b2-bdfc-afd022282067@kernel.dk>
On Thu, Oct 14, 2021 at 12:34:55PM -0600, Jens Axboe wrote:
> This generates a lot better code for me, and bumps performance from
> 7650K IOPS to 7750K IOPS. Looking at profiles for the run and running
> perf diff, it confirms that we're now sending a lot less time there:
>
> 6.38% -2.80% [kernel.vmlinux] [k] blkdev_direct_IO
>
> Taking it from the 2nd most cycle consumer to only the 9th most at
> 3.35% of the CPU time.
Kinda weird that the overhead is so big. That being said for more
than a single flag I prefer the bit ops anyway, this code just
"evolved".
Reviewed-by: Christoph Hellwig <hch@lst.de>
prev parent reply other threads:[~2021-10-16 4:30 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-14 18:34 [PATCH] block: use flags instead of bit fields for blkdev_dio Jens Axboe
2021-10-16 4:30 ` Christoph Hellwig [this message]
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