netdev - Re: [RFC PATCH] netfilter: remove the duplicate tables

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, 19 Nov 2010 13:57:22 +0100 (CET)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	Changli Gao <xiaosuo@...il.com>
cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	Stephen Hemminger <shemminger@...tta.com>
Subject: Re: [RFC PATCH] netfilter: remove the duplicate tables

On Friday 2010-11-19 13:48, Changli Gao wrote:

>On Fri, Nov 19, 2010 at 7:29 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>>
>> IMHO, the real problem is not the table duplication. We know that adding
>> a level of indirection is going to hurt a lot because of cache misses.
>>
>
>Currently, multi-core CPU is common, the cores in a CPU share the
>lowest level cache. Duplicate tables use more RAM, and may cause more
>pressure of the lowest level cache.

There probably should be at most one copy per NUMA node. Maybe less, 
depending on what the benchmarks will say.

I started on some patch to reduce the ruleset from #cpu to #numa_nodes, 
but then stopped when I ran into the obvious fact that it would require 
locking the counters because xtables can actually run on more than one 
core within a given numa node. When decoupling counters from the 
ruleset, reducing the ruleset copies would become easier.
--
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