From: Jens Axboe <axboe@fb.com>
To: Ming Lei <ming.lei@redhat.com>,
linux-block@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH] mtip32xx: avoid to read HOST_CAP from HW in .queue_rq()
Date: Wed, 5 Jul 2017 12:11:02 -0600 [thread overview]
Message-ID: <5b272cd9-3479-6b79-312d-11f1dedc7ed0@fb.com> (raw)
In-Reply-To: <20170705041427.9887-1-ming.lei@redhat.com>
On 07/04/2017 10:14 PM, Ming Lei wrote:
> It is observed reading the register from HW takes a bit long,
> for example in my box, the following difference of 'perf report
> --no-children fio ...' can be seen when running I/O:
>
> 1) V4.12 without patch
> + 9.28% fio [mtip32xx] [k] mtip_irq_handler
> + 8.48% fio [mtip32xx] [k] mtip_init_cmd_header
>
> 2) V4.12 with the following patch
> + 9.14% fio [mtip32xx] [k] mtip_irq_handler
> ......
> + 1.14% fio [mtip32xx] [k] mtip_init_cmd_header
>
> IOPS can be increased by ~5% with this patch too.
Thanks, this is definitely problematic since we don't just do it
at init time anymore. Applied for 4.13.
--
Jens Axboe
prev parent reply other threads:[~2017-07-05 18:11 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-05 4:14 [PATCH] mtip32xx: avoid to read HOST_CAP from HW in .queue_rq() Ming Lei
2017-07-05 18:01 ` Christoph Hellwig
2017-07-05 18:11 ` Jens Axboe [this message]
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