From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>, [email protected]
Subject: Re: [PATCH 3/3] io_uring: follow **iovec idiom in io_import_iovec
Date: Mon, 13 Jul 2020 15:16:28 -0600 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 7/13/20 3:12 PM, Pavel Begunkov wrote:
> On 14/07/2020 00:09, Jens Axboe wrote:
>> On 7/13/20 1:59 PM, Pavel Begunkov wrote:
>>> @@ -3040,8 +3040,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
>>> }
>>> }
>>> out_free:
>>> - if (!(req->flags & REQ_F_NEED_CLEANUP))
>>> - kfree(iovec);
>>> + kfree(iovec);
>>> return ret;
>>> }
>>
>> Faster to do:
>>
>> if (iovec)
>> kfree(iovec)
>>
>> to avoid a stupid call. Kind of crazy, but I just verified with this one
>> as well that it's worth about 1.3% CPU in my stress test.
>
> That looks crazy indeed
I suspect what needs to happen is that kfree should be something ala:
static inline void kfree(void *ptr)
{
if (ptr)
__kfree(ptr);
}
to avoid silly games like this. Needs to touch all three slab
allocators, though definitely in the trivial category.
--
Jens Axboe
next prev parent reply other threads:[~2020-07-13 21:16 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-13 19:59 [PATCH for-5.9 0/3] rw iovec copy cleanup Pavel Begunkov
2020-07-13 19:59 ` [PATCH 1/3] io_uring: simplify io_req_map_rw() Pavel Begunkov
2020-07-13 19:59 ` [PATCH 2/3] io_uring: add a helper for async rw iovec prep Pavel Begunkov
2020-07-13 19:59 ` [PATCH 3/3] io_uring: follow **iovec idiom in io_import_iovec Pavel Begunkov
2020-07-13 21:09 ` Jens Axboe
2020-07-13 21:12 ` Pavel Begunkov
2020-07-13 21:16 ` Jens Axboe [this message]
2020-07-13 21:18 ` Pavel Begunkov
2020-07-13 21:26 ` Jens Axboe
2020-07-13 21:09 ` [PATCH for-5.9 0/3] rw iovec copy cleanup Jens Axboe
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