netdev - Re: [PATCH net] tcp/dccp: do not block bh too long in inet_twdr_twkill

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]

Date:	Fri, 10 Apr 2015 08:31:01 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] tcp/dccp: do not block bh too long in
 inet_twdr_twkill_work()

On Fri, 2015-04-10 at 04:19 -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> I have seen inet_twdr_twkill_work() blocking softirq for
> periods up to 1.5 seconds, depending on number of timewait sockets.
> 
> This is an unacceptable source of latency.
> 
> Note that inet_twdr_do_twkill_work() releases death_lock spinlock
> for every tw handled, but does not take care of bh enabling.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---

BTW, inet_twdr_twcal_tick() suffers from similar problem, with latencies
of ~25ms, when /proc/sys/net/ipv4/tcp_tw_recycle is enabled.

Since it holds death_lock for the whole run, all other cpus are spinning
on it.

I believe we simply should add a timer per timewait, as I did for
request sockets.

This would simplify the code a lot, and would get rid of this awful non
scalable timer wheel.


--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html