netdev - Re: [PATCH] INET : removes per bucket rwlock in tcp/dccp ehash table

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:	Wed, 07 Nov 2007 02:41:14 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	dada1@...mosbay.com
Cc:	ak@...e.de, netdev@...r.kernel.org, acme@...hat.com, jarkao2@...pl
Subject: Re: [PATCH] INET : removes per bucket rwlock in tcp/dccp ehash
 table

From: Eric Dumazet <dada1@...mosbay.com>
Date: Sun, 04 Nov 2007 12:31:28 +0100

> [PATCH] INET : removes per bucket rwlock in tcp/dccp ehash table
> 
> As done two years ago on IP route cache table (commit 
> 22c047ccbc68fa8f3fa57f0e8f906479a062c426) , we can avoid using one lock per 
> hash bucket for the huge TCP/DCCP hash tables.
> 
> On a typical x86_64 platform, this saves about 2MB or 4MB of ram, for litle 
> performance differences. (we hit a different cache line for the rwlock, but 
> then the bucket cache line have a better sharing factor among cpus, since we 
> dirty it less often). For netstat or ss commands that want a full scan of hash 
> table, we perform fewer memory accesses.
> 
> Using a 'small' table of hashed rwlocks should be more than enough to provide 
> correct SMP concurrency between different buckets, without using too much 
> memory. Sizing of this table depends on num_possible_cpus() and various CONFIG 
> settings.
> 
> This patch provides some locking abstraction that may ease a future work using 
>   a different model for TCP/DCCP table.
> 
> Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
> Acked-by: Arnaldo Carvalho de Melo <acme@...hat.com>

I'm going to push this current version to Linus, the space saving
really justify it and if we want to refine things further we do it
with followon work rather than blocking this patch.

Thanks Eric!
-
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