From: Jens Axboe <axboe@kernel.dk>
To: Zhengyuan Liu <liuzhengyuan@kylinos.cn>
Cc: linux-block@vger.kernel.org
Subject: Re: [PATCH 3/3] io_uring: use kmem_cache to alloc sqe
Date: Mon, 15 Jul 2019 07:52:50 -0600 [thread overview]
Message-ID: <6059ea46-b87f-e8e9-5e41-47b77f4c4c60@kernel.dk> (raw)
In-Reply-To: <5d2c1314.1c69fb81.ecfb1.bf96SMTPIN_ADDED_BROKEN@mx.google.com>
On 7/14/19 11:45 PM, Zhengyuan Liu wrote:
>
> On 7/15/19 11:51 AM, Jens Axboe wrote:
>> On Jul 14, 2019, at 9:38 PM, Zhengyuan Liu <liuzhengyuan@kylinos.cn> wrote:
>>>
>>>> On 7/14/19 5:44 AM, Jens Axboe wrote:
>>>>> On 7/12/19 10:54 PM, Zhengyuan Liu wrote:
>>>>> As we introduced three lists(async, defer, link), there could been
>>>>> many sqe allocation. A natural idea is using kmem_cache to satisfy
>>>>> the allocation just like io_kiocb does.
>>>> A change like this needs to come with some performance numbers
>>>> or utilization numbers showing the benefit. I have considered
>>>> doing this before, but just never got around to testing if it's
>>>> worth while or not.
>>>> Have you?
>>> I only did some simple testing with fio. The benefit was deeply depend on the IO scenarios. For random and direct IO , it appears to be nearly no seq copying, but for buffered sequential rw, it appears to be more than 60% copying compared to original submition.
>> Right, which is great as it’s then working as designed! But my
>> question was, for that sequential case, what kind of speed up (or
>> reduction in overhead) do you see from allocating the unit out of
>> slab vs kmalloc? There has to be a win there for the change to be
>> worthwhile.
>
> Thanks for your comments Jens. No speed up indeed in overhead from my
> testing.
Then I suggest we just drop this change, it only makes sense if there's
a win.
--
Jens Axboe
prev parent reply other threads:[~2019-07-15 13:52 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-13 4:54 [PATCH 3/3] io_uring: use kmem_cache to alloc sqe Zhengyuan Liu
2019-07-13 21:44 ` Jens Axboe
[not found] ` <5d2bf52d.1c69fb81.af3a2.b57fSMTPIN_ADDED_BROKEN@mx.google.com>
2019-07-15 3:51 ` Jens Axboe
[not found] ` <5d2c1314.1c69fb81.ecfb1.bf96SMTPIN_ADDED_BROKEN@mx.google.com>
2019-07-15 13:52 ` Jens Axboe [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6059ea46-b87f-e8e9-5e41-47b77f4c4c60@kernel.dk \
--to=axboe@kernel.dk \
--cc=linux-block@vger.kernel.org \
--cc=liuzhengyuan@kylinos.cn \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).