netdev - Re: [PATCH v2 net-next] tcp: avoid expensive pskb_expand

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: <4F9053FD.4060509@hp.com>
Date:	Thu, 19 Apr 2012 11:05:49 -0700
From:	Rick Jones <rick.jones2@...com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>,
	Neal Cardwell <ncardwell@...gle.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Tom Herbert <therbert@...gle.com>,
	Maciej Żenczykowski <maze@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH v2 net-next] tcp: avoid expensive pskb_expand_head() calls


>> That or bare ACKs have to be excluded from the overhead checks somehow I
>> guess, or there be more aggressive copying into smaller buffers.
>>
>
> Nope, we need a limit or risk OOM if a malicious peer send ACK flood ;)

Well, there is that...

>
> To be clear, if I change the tcp_rmem[1] from 87380 to big value, I no
> longer have ACK drops, but still poor performance, I am still
> investigating.

What happens if you set net.core.[rw]mem_max to 4 MB and then use 
something like -s 1M -S 1M in netperf?

netperf -t TCP_STREAM -H <remote> -- -s 1M -S 1M -m 64K

(or -m 16K if you want to keep the send size the same as your previous 
tests...)

rick
--
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