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, 16 Jun 2010 11:10:07 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Mitchell Erblich <erblichs@...thlink.net>
Cc:	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Subject: Re: Proposed linux kernel changes : scaling  tcp/ip stack

Mitchell Erblich <erblichs@...thlink.net> writes:
>
> Summary: Don't use last free pages for TCP ACKs with GFP_ATOMIC for our
> sk buf allocs. 1 line change in tcp_output.c with a new gfp.h arg, and a change
> in the generic kernel. TBD.
>
> This change should have no effect with normal available kernel mem allocs.
>
> Assuming memory pressure ( WAITING for clean memory) we should be allocating
> our last pages for input skbufs and not for xmit allocs.

How about you instrument a kernel and measure if this really happens
frequently under reasonable loads?  That is you can probably
use the existing dropped page counters in netstat 
Stephen added some time ago.

Since soft irqs cannot really wait exhausted GFP_ATOMIC would normally
lead to dropped packets. FWIW I am not aware of any serious dropped
packets problem on normal loads.

Running a kernel with nearly zero free memory is dangerous anyways
-- pretty much any kernel service can fail arbitarily --
if this happened frequently I suspect we would need generic
VM solution for it.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
--
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

Powered by blists - more mailing lists