netdev - Re: [PATCH] ipv4: Add sysctl knob to control early socket demux

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: <20120622.171509.1112294083000632011.davem@davemloft.net>
Date:	Fri, 22 Jun 2012 17:15:09 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	alexander.h.duyck@...el.com
Cc:	netdev@...r.kernel.org, jeffrey.t.kirsher@...el.com,
	edumazet@...gle.com
Subject: Re: [PATCH] ipv4: Add sysctl knob to control early socket demux

From: Alexander Duyck <alexander.h.duyck@...el.com>
Date: Thu, 21 Jun 2012 16:58:31 -0700

> This change is meant to add a control for disabling early socket demux.
> The main motivation behind this patch is to provide an option to disable
> the feature as it adds an additional cost to routing that reduces overall
> throughput by up to 5%.  For example one of my systems went from 12.1Mpps
> to 11.6 after the early socket demux was added.  It looks like the reason
> for the regression is that we are now having to perform two lookups, first
> the one for an established socket, and then the one for the routing table.
> 
> By adding this patch and toggling the value for ip_early_demux to 0 I am
> able to get back to the 12.1Mpps I was previously seeing.
> 
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>

I applied this for now, making a minor change to move the local
variables down into the new basic block you created.

There has got to be a way to make this really cheap.  At the very
least we can have the GRO code store away the ports and therefore
allow us to just do a direct call to try and demux the socket.  Thus,
we'd avoid all of pskb_may_pull() et al. packet validations, and
packet header pointer calculations.

Furthermore, we can reduce to overhead by making a special inet
established hash demux that doesn't check for time-wait sockets,
reducing the number of probes to 1 from 2.
--
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