From: Jens Axboe <axboe@kernel.dk>
To: Kanchan Joshi <joshi.k@samsung.com>
Cc: linux-block@vger.kernel.org, kbusch@kernel.org
Subject: Re: [PATCH 2/3] block: enable bio caching use for passthru IO
Date: Sun, 7 Aug 2022 12:45:19 -0600 [thread overview]
Message-ID: <a59f6328-b81a-c529-7553-2bef94f9b5a2@kernel.dk> (raw)
In-Reply-To: <20220807180855.GA30655@test-zns>
On 8/7/22 12:08 PM, Kanchan Joshi wrote:
> On Sat, Aug 06, 2022 at 09:20:03AM -0600, Jens Axboe wrote:
>> bdev based polled O_DIRECT is currently quite a bit faster than
>> passthru on the same device, and one of the reaons is that we're not
>> able to use the bio caching for passthru IO.
>>
>> If REQ_POLLED is set on the request, use the fs bio set for grabbing a
>> bio from the caches, if available. This saves 5-6% of CPU over head
>> for polled passthru IO.
>
> For passthru path, bio is always freed in the task-context (and not in
> irq) so must this be tied to polled-io only?
Right, that's why it's tied to polled. If polling gets cleared, then it
will be freed normally on completion rather than inserted into the
cache.
I do have patches for irq bio caching too, that'll work fine with
io_uring:
https://git.kernel.dk/cgit/linux-block/commit/?h=perf-wip&id=ab3d4371227a34a5561e4d594a17baaad03bf1b7
I'll post that too, would be nice if we can figure out a clean way to do
this. I have posted it before, iirc.
--
Jens Axboe
next prev parent reply other threads:[~2022-08-07 18:45 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-06 15:20 [PATCHSET 0/3] passthru block optimizations Jens Axboe
2022-08-06 15:20 ` [PATCH 1/3] block: shrink rq_map_data a bit Jens Axboe
2022-08-07 9:26 ` Chaitanya Kulkarni
2022-08-06 15:20 ` [PATCH 2/3] block: enable bio caching use for passthru IO Jens Axboe
2022-08-07 9:27 ` Chaitanya Kulkarni
2022-08-07 18:08 ` Kanchan Joshi
2022-08-07 18:45 ` Jens Axboe [this message]
2022-08-06 15:20 ` [PATCH 3/3] block: use on-stack page vec for <= UIO_FASTIOV Jens Axboe
2022-08-07 9:30 ` Chaitanya Kulkarni
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