netdev - Re: cat /proc/net/tcp takes 0.5 seconds on x86

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20080827144800.5f9fc5b4@extreme>
Date:	Wed, 27 Aug 2008 14:48:00 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	David Miller <davem@...emloft.net>
Cc:	andi@...stfloor.org, davej@...hat.com, netdev@...r.kernel.org,
	j.w.r.degoede@....nl
Subject: Re: cat /proc/net/tcp takes 0.5 seconds on x86_64

On Wed, 27 Aug 2008 14:29:41 -0700 (PDT)
David Miller <davem@...emloft.net> wrote:

> From: Andi Kleen <andi@...stfloor.org>
> Date: Wed, 27 Aug 2008 14:41:52 +0200
> 
> > Dave Jones <davej@...hat.com> writes:
> > 
> > > Just had this bug reported against our development tree..
> > 
> > SUSE had an old patch for this which unfortunately got rejected 
> > some time ago for some bogus reason.
> 
> Really, your patch fixes this specific slowdown that got introduced
> recently?  I really doubt it Andi, so please don't use this as an
> opportunity to toot your own horn, thanks.
> --
> 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

I do wonder if having large hash table actually helps? When TCP hash
table gets too big, it means every lookup is a cache miss. Assuming
a busy server with 2000 connections and perfect hash. On a 4G mem x86-64
we are doing 512K hash entries which is ridiculous. Something like 64K
entries is more than enough.
--
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