From: David Gibson <david@gibson.dropbear.id.au>
To: Stefano Brivio <sbrivio@redhat.com>
Cc: passt-dev@passt.top
Subject: Re: [PATCH v2 17/18] udp: Use tap_send_frames()
Date: Thu, 5 Jan 2023 15:54:02 +1100 [thread overview]
Message-ID: <Y7ZX6oovRQT7ytbY@yekko> (raw)
In-Reply-To: <20230104184525.31fc2f87@elisabeth>
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On Wed, Jan 04, 2023 at 06:45:25PM +0100, Stefano Brivio wrote:
> On Fri, 9 Dec 2022 16:42:27 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
>
> > To send frames on the tap interface, the UDP uses a fairly complicated two
> > level batching. First multiple frames are gathered into a single "message"
> > for the qemu stream socket, then multiple messages are send with
> > sendmmsg(). We now have tap_send_frames() which already deals with sending
> > a number of frames, including batching and handling partial sends. Use
> > that to considerably simplify things.
> >
> > This does make a couple of behavioural changes:
> > * We no longer split messages to keep them under 64kiB, which comments
> > say is necessary. However the TCP code didn't have equivalent code, so
> > either this isn't actually needed, or we should implement for both
> > (which is now easier since it can be done in one place).
>
> That used to be SHRT_MAX (32 KiB - 1), not 64 KiB. For some reason, if
> I sent messages with multiple frames, with any one of them larger than
> 32 KiB, qemu used to close the connection.
>
> But it looks like this was caused by some issue in the handling of short
> sends rather than an issue in qemu, especially given that, with this
> series applied, I don't hit the original issue (and I could predictably
> reproduce it earlier).
Right, I already updated the commit messages and some comments based
on the discussion we had last night.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2023-01-05 5:45 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-09 5:42 [PATCH v2 00/18] RFC: Unify and simplify tap send path David Gibson
2022-12-09 5:42 ` [PATCH v2 01/18] pcap: Introduce pcap_frame() helper David Gibson
2023-01-04 17:45 ` Stefano Brivio
2023-01-05 4:47 ` David Gibson
2022-12-09 5:42 ` [PATCH v2 02/18] pcap: Replace pcapm() with pcap_multiple() David Gibson
2022-12-09 5:42 ` [PATCH v2 03/18] tcp: Combine two parts of passt tap send path together David Gibson
2022-12-09 5:42 ` [PATCH v2 04/18] tcp: Don't keep compute total bytes in a message until we need it David Gibson
2023-01-04 17:45 ` Stefano Brivio
2023-01-05 4:48 ` David Gibson
2022-12-09 5:42 ` [PATCH v2 05/18] tcp: Improve interface to tcp_l2_buf_flush() David Gibson
2023-01-04 17:45 ` Stefano Brivio
2023-01-05 4:53 ` David Gibson
2022-12-09 5:42 ` [PATCH v2 06/18] tcp: Combine two parts of pasta tap send path together David Gibson
2022-12-09 5:42 ` [PATCH v2 07/18] tap, tcp: Move tap send path to tap.c David Gibson
2022-12-09 5:42 ` [PATCH v2 08/18] util: Introduce hton*_constant() in place of #ifdefs David Gibson
2022-12-09 5:42 ` [PATCH v2 09/18] tcp, udp: Use named field initializers in iov_init functions David Gibson
2022-12-09 5:42 ` [PATCH v2 10/18] util: Parameterize ethernet header initializer macro David Gibson
2022-12-09 5:42 ` [PATCH v2 11/18] tcp: Remove redundant and incorrect initialization from *_iov_init() David Gibson
2022-12-09 5:42 ` [PATCH v2 12/18] tcp: Consolidate calculation of total frame size David Gibson
2022-12-09 5:42 ` [PATCH v2 13/18] tap: Add "tap headers" abstraction David Gibson
2022-12-09 5:42 ` [PATCH v2 14/18] tcp: Use abstracted tap header David Gibson
2022-12-09 5:42 ` [PATCH v2 15/18] tap: Use different io vector bases depending on tap type David Gibson
2022-12-09 5:42 ` [PATCH v2 16/18] udp: Use abstracted tap header David Gibson
2022-12-09 5:42 ` [PATCH v2 17/18] udp: Use tap_send_frames() David Gibson
2023-01-04 17:45 ` Stefano Brivio
2023-01-05 4:54 ` David Gibson [this message]
2022-12-09 5:42 ` [PATCH v2 18/18] tap: Improve handling of partial frame sends David Gibson
2023-01-04 17:45 ` Stefano Brivio
2023-01-05 4:57 ` David Gibson
2023-01-04 17:45 ` [PATCH v2 00/18] RFC: Unify and simplify tap send path Stefano Brivio
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