From: Jens Axboe <[email protected]>
To: "Pavel Begunkov" <[email protected]>,
io-uring <[email protected]>, 李通洲 <[email protected]>
Subject: Re: [RFC] single cqe per link
Date: Mon, 24 Feb 2020 19:24:09 -0700 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 2/24/20 5:39 PM, Pavel Begunkov wrote:
> I've got curious about performance of the idea of having only 1 CQE per link
> (for the failed or last one). Tested it with a quick dirty patch doing
> submit-and-reap of a nops-link (patched for inline execution).
>
> 1) link size: 100
> old: 206 ns per nop
> new: 144 ns per nop
>
> 2) link size: 10
> old: 234 ns per nop
> new: 181 ns per nop
>
> 3) link size: 10, FORCE_ASYNC
> old: 667 ns per nop
> new: 569 ns per nop
>
>
> The patch below breaks sequences, linked_timeout and who knows what else.
> The first one requires synchronisation/atomic, so it's a bit in the way. I've
> been wondering, whether IOSQE_IO_DRAIN is popular and how much it's used. We can
> try to find tradeoff or even disable it with this feature.
For a more realistic workload, I can try and run a random read workload
on a fast device. If I just make the QD the link count, then we'll
have the same amount in parallel, just with link-depth ratio less
CQEs. I'd be curious to see what that does.
--
Jens Axboe
prev parent reply other threads:[~2020-02-25 2:24 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-25 0:39 [RFC] single cqe per link Pavel Begunkov
2020-02-25 2:14 ` Carter Li 李通洲
2020-02-25 2:36 ` Jens Axboe
2020-02-25 3:13 ` Jens Axboe
2020-02-25 10:12 ` Pavel Begunkov
2020-02-25 20:20 ` Jens Axboe
2020-02-25 21:13 ` Pavel Begunkov
2020-08-21 5:17 ` Questions about IORING_OP_ASYNC_CANCEL usage Carter Li 李通洲
2020-08-21 5:20 ` Carter Li 李通洲
2020-02-25 2:24 ` Jens Axboe [this message]
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