From: Jens Axboe <axboe@kernel.dk>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-block@vger.kernel.org
Subject: Re: [PATCH 2/4] block: inline fast path of driver tag allocation
Date: Wed, 13 Oct 2021 12:07:08 -0600 [thread overview]
Message-ID: <dfddae28-7ddb-0365-24e0-79aab9351983@kernel.dk> (raw)
In-Reply-To: <YWcd7NzLHv9Qt7Lx@infradead.org>
On 10/13/21 11:57 AM, Christoph Hellwig wrote:
> On Wed, Oct 13, 2021 at 11:46:04AM -0600, Jens Axboe wrote:
>> On 10/13/21 11:22 AM, Christoph Hellwig wrote:
>>> On Wed, Oct 13, 2021 at 10:49:35AM -0600, Jens Axboe wrote:
>>>> If we don't use an IO scheduler or have shared tags, then we don't need
>>>> to call into this external function at all. This saves ~2% for such
>>>> a setup.
>>>
>>> Hmm. What happens if you just throw an inline tag onto
>>> blk_mq_get_driver_tag?
>>
>> I'd be surprised if that's any different than my patch in terms of
>> performance, the fast path would be about the same. I don't feel
>> strongly about it, can do that instead.
>
> I find the double indirection in your patch a bit confusing. Not a big
> deal if it is actually required, but if we can avoid that I'd prefer
> not to add the extra indirection.
Tested the variants, and it does seem to be the best one...
--
Jens Axboe
next prev parent reply other threads:[~2021-10-13 18:07 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-13 16:49 [PATCHSET 0/4] Various block optimizations Jens Axboe
2021-10-13 16:49 ` [PATCH 1/4] block: provide helpers for rq_list manipulation Jens Axboe
2021-10-13 17:11 ` Christoph Hellwig
2021-10-13 17:47 ` Jens Axboe
2021-10-13 16:49 ` [PATCH 2/4] block: inline fast path of driver tag allocation Jens Axboe
2021-10-13 17:22 ` Christoph Hellwig
2021-10-13 17:46 ` Jens Axboe
2021-10-13 17:57 ` Christoph Hellwig
2021-10-13 18:07 ` Jens Axboe [this message]
2021-10-13 16:49 ` [PATCH 3/4] block: don't bother iter advancing a fully done bio Jens Axboe
2021-10-13 17:26 ` Christoph Hellwig
2021-10-13 17:46 ` Jens Axboe
2021-10-13 16:49 ` [PATCH 4/4] block: move update request helpers into blk-mq.c Jens Axboe
2021-10-13 17:32 ` Christoph Hellwig
2021-10-13 17:46 ` Jens Axboe
2021-10-13 17:54 ` Christoph Hellwig
2021-10-13 17:57 ` Jens Axboe
2021-10-14 5:00 ` Christoph Hellwig
2021-10-14 15:14 ` Jens Axboe
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