netdev - Re: [PATCH] myr10ge: again fix lro_gen

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]

Message-ID: <49F1F350.2080402@hp.com>
Date:	Fri, 24 Apr 2009 10:13:52 -0700
From:	Rick Jones <rick.jones2@...com>
To:	Andrew Gallatin <gallatin@...i.com>
CC:	Herbert Xu <herbert@...dor.apana.org.au>,
	David Miller <davem@...emloft.net>, brice@...i.com,
	sgruszka@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH] myr10ge: again fix lro_gen_skb() alignment

> This is strange.  I wonder if it might be a cache footprint issue?
> My intentionally weak receiver is an athlon64 x2 "Toledo", and
> has only 512KB L2 cache.  I can re-test with a core-2 based Xeon.

A point about netperf :)  By default, it will use one more buffer than the 
initial size of the socket buffer divided by the send/recv buffer size - this 
goes back to days of copy-avoidance, a flavor of which can be found in reading:

ftp://ftp.cup.hp.com/dist/networking/briefs/copyavoid.pdf

particularly section 3.2.  It can be overridden with the global -W option:

     -W send,recv      Set the number of send,recv buffers

Of course, this will interact with other things such as:

The default send/recv size will be the send/recv socket buffer size. That can be 
overridden with the test-specific -m/-M options.

The default socket buffer size will be whatever the system gives it.  That can be 
overridden with the test-specific -s/-S options.

So, the various options can have a non-trivial effect on the cache footprint of 
the data netperf is shoving around.

rick jones
--
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