netdev - RE: make sendmsg/recvmsg process multiple messages at once

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Tue, 2 Feb 2021 15:19:21 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Paolo Abeni' <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Menglong Dong <menglong8.dong@...il.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>
CC:     netdev <netdev@...r.kernel.org>
Subject: RE: make sendmsg/recvmsg process multiple messages at once

From: Paolo Abeni
> Sent: 02 February 2021 10:19
...
> Note that you can already process several packets with a single syscall
> using sendmmsg/recvmmsg. Both have issues with error reporting and
> timeout and IIRC still don't amortize the overhead introduced e.g. by
> CONFIG_HARDENED_USERCOPY.

Both CONFIG_HARDENED_USERCOPY and the extra user copies needed
even for sendmsg() over send() are definitely measurable.
I've run tests using _copy_from_user() for many of the copies.
Even the cost of reading in a single iov[] for the buffer
affects things.

My last attempt at speeding up writev("/dev/null", iov, 10)
fell into the rabbit hole of io_uring (again).
But the partial changes gave a few % improvement.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)