From: Stefan Metzmacher <[email protected]>
To: Pavel Begunkov <[email protected]>,
[email protected], [email protected]
Cc: Jakub Kicinski <[email protected]>, [email protected]
Subject: Re: [PATCH 5/5] io_uring/notif: let userspace know how effective the zero copy usage was
Date: Sat, 17 Sep 2022 12:24:48 +0200 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
Am 17.09.22 um 11:22 schrieb Pavel Begunkov:
> On 9/16/22 22:36, Stefan Metzmacher wrote:
>> The 2nd cqe for IORING_OP_SEND_ZC has IORING_CQE_F_NOTIF set in cqe->flags
>> and it will now have the number of successful completed
>> io_uring_tx_zerocopy_callback() callbacks in the lower 31-bits
>> of cqe->res, the high bit (0x80000000) is set when
>> io_uring_tx_zerocopy_callback() was called with success=false.
>
> It has a couple of problems, and because that "simplify uapi"
> patch is transitional it doesn't go well with what I'm queuing
> for 6.1, let's hold it for a while.
Once the current behavior gets released stable, we're no
longer able to change the meaning of cqe.res.
As cqe.res == 0 would mean zero copy wasn't used at all,
which would be the indication for userspace to avoid using SEND_ZC.
But if 6.0 would always return cqe.res = 0, there's no chance for
userspace to have a detection strategy.
And I don't think it will cause a lot of trouble for your 6.1 stuff (assuming
you mean your SENDMSG_ZC code), I was already having that on top
of my test branches, the current one is:
https://git.samba.org/?p=metze/linux/wip.git;a=shortlog;h=refs/heads/io_uring-6.0.0-rc5-metze.08
I plan to test SENDMSG_ZC with Samba next week.
metze
next prev parent reply other threads:[~2022-09-17 10:25 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-16 21:36 [PATCH for-6.0 0/5] IORING_OP_SEND_ZC improvements Stefan Metzmacher
2022-09-16 21:36 ` [PATCH 1/5] io_uring/opdef: rename SENDZC_NOTIF to SEND_ZC Stefan Metzmacher
2022-09-17 9:17 ` Pavel Begunkov
2022-09-16 21:36 ` [PATCH 2/5] io_uring/core: move io_cqe->fd over from io_cqe->flags to io_cqe->res Stefan Metzmacher
2022-09-16 21:36 ` [PATCH 3/5] io_uring/core: keep req->cqe.flags on generic errors Stefan Metzmacher
2022-09-16 21:36 ` [PATCH 4/5] io_uring/net: let io_sendzc set IORING_CQE_F_MORE before sock_sendmsg() Stefan Metzmacher
2022-09-16 21:36 ` [PATCH 5/5] io_uring/notif: let userspace know how effective the zero copy usage was Stefan Metzmacher
2022-09-17 9:22 ` Pavel Begunkov
2022-09-17 10:24 ` Stefan Metzmacher [this message]
2022-09-21 12:04 ` Pavel Begunkov
2022-09-21 12:33 ` Stefan Metzmacher
2022-09-17 9:16 ` [PATCH for-6.0 0/5] IORING_OP_SEND_ZC improvements Pavel Begunkov
2022-09-17 10:44 ` Stefan Metzmacher
2022-09-21 11:39 ` Pavel Begunkov
2022-09-21 12:18 ` Stefan Metzmacher
2022-09-21 12:58 ` Pavel Begunkov
2022-09-18 22:49 ` (subset) " Jens Axboe
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