netdev - Re: Same data to several sockets with just one syscall ?

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

Message-ID: <1455273356.31770.1.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 12 Feb 2016 02:35:56 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Claudio Scordino <claudio@...dence.eu.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Same data to several sockets with just one syscall ?

On Fri, 2016-02-12 at 09:53 +0100, Claudio Scordino wrote:

> This makes the application waste time in entering/exiting the kernel
> level several times.

syscall overhead is usually small. Real cost is actually getting to the
socket objects (fd manipulation), that you wont avoid with a
super-syscall anyway.

> Moreover, if I'm not wrong, the kernel is free to execute pending work
> (e.g., softirqs) when returning from a syscall, making the application
> experience further latency.

Well, sofirqs can happen even in the middle of syscalls, not only at the
end of them.