netdev - Re: [PATCH] iptables: lock free counters

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:	Thu, 19 Feb 2009 17:03:18 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Rick Jones <rick.jones2@...com>
Cc:	Eric Dumazet <dada1@...mosbay.com>,
	David Miller <davem@...emloft.net>,
	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH] iptables: lock free counters

On Thu, 19 Feb 2009 15:56:18 -0800
Rick Jones <rick.jones2@...com> wrote:

> Eric Dumazet wrote:
> > Stephen Hemminger a écrit :
> > 
> >>The reader/writer lock in ip_tables is acquired in the critical path of
> >>processing packets and is one of the reasons just loading iptables can cause
> >>a 20% performance loss. The rwlock serves two functions:
> >>
> >>1) it prevents changes to table state (xt_replace) while table is in use.
> >>   This is now handled by doing rcu on the xt_table. When table is
> >>   replaced, the new table(s) are put in and the old one table(s) are freed
> >>   after RCU period.
> >>
> >>2) it provides synchronization when accesing the counter values.
> >>   This is now handled by swapping in new table_info entries for each cpu
> >>   then summing the old values, and putting the result back onto one
> >>   cpu.  On a busy system it may cause sampling to occur at different
> >>   times on each cpu, but no packet/byte counts are lost in the process.
> >>
> >>Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
> > 
> > 
> > 
> > Acked-by: Eric Dumazet <dada1@...mosbay.com>
> > 
> > Sucessfully tested on my dual quad core machine too, but iptables only (no
> > ipv6 here)
> > 
> > BTW, my new "tbench 8" result is 2450 MB/s, (it was 2150 MB/s not so long ago)
> > 
> > Thanks Stephen, thats very cool stuff, yet another rwlock out of kernel :)
> 
> Do you folks need/want further testing against the 32-core setup?

It would be good to combine all 3 (iptables-rcu, timer change, and conntrack lock)
to see what the overhead change is.
--
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