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io_uring/net: introduce IORING_SEND_ZC_REPORT_USAGE flag

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It might be useful for applications to detect if a zero copy transfer with
SEND[MSG]_ZC was actually possible or not. The application can fallback to
plain SEND[MSG] in order to avoid the overhead of two cqes per request. Or
it can generate a log message that could indicate to an administrator that
no zero copy was possible and could explain degraded performance.

Cc: stable@vger.kernel.org # 6.1
Link: https://lore.kernel.org/io-uring/fb6a7599-8a9b-15e5-9b64-6cd9d01c6ff4@gmail.com/T/#m2b0d9df94ce43b0e69e6c089bdff0ce6babbdfaa
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8945b01756d902f5d5b0667f20b957ad3f742e5e.1666895626.git.metze@samba.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Stefan Metzmacher
2022-10-27 20:34:45 +02:00
committed by Jens Axboe
parent eb7081409f
commit e307e66981
4 changed files with 38 additions and 1 deletions
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6
io_uring/net.c
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@ -937,7 +937,8 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
zc->flags = READ_ONCE(sqe->ioprio);
if (zc->flags & ~(IORING_RECVSEND_POLL_FIRST |
IORING_RECVSEND_FIXED_BUF))
IORING_RECVSEND_FIXED_BUF |
IORING_SEND_ZC_REPORT_USAGE))
return -EINVAL;
notif = zc->notif = io_alloc_notif(ctx);
if (!notif)
@ -955,6 +956,9 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
req->imu = READ_ONCE(ctx->user_bufs[idx]);
io_req_set_rsrc_node(notif, ctx, 0);
}
if (zc->flags & IORING_SEND_ZC_REPORT_USAGE) {
io_notif_to_data(notif)->zc_report = true;
}
if (req->opcode == IORING_OP_SEND_ZC) {
if (READ_ONCE(sqe->__pad3[0]))