netdev - Re: Loopback performance from kernel 2.6.12 to 2.6.37

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Message-ID: <1289284933.2790.91.camel@edumazet-laptop>
Date:	Tue, 09 Nov 2010 07:42:13 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andrew Hendry <andrew.hendry@...il.com>
Cc:	Jesper Dangaard Brouer <jdb@...x.dk>,
	netdev <netdev@...r.kernel.org>
Subject: Re: Loopback performance from kernel 2.6.12 to 2.6.37

Le mardi 09 novembre 2010 à 07:38 +0100, Eric Dumazet a écrit :

> Hmm, your clock source is HPET, that might explain the problem on a
> scheduler intensive workload.
> 

And if a packet sniffer (dhclient for example) makes all packets being
timestamped, it also can explain a slowdown, even if there is no
scheduler artifacts.

cat /proc/net/packet

> My HP dev machine
> # grep . /sys/devices/system/clocksource/clocksource0/*
> /sys/devices/system/clocksource/clocksource0/available_clocksource:tsc hpet acpi_pm 
> /sys/devices/system/clocksource/clocksource0/current_clocksource:tsc
> 
> My laptop:
> $ grep . /sys/devices/system/clocksource/clocksource0/*
> /sys/devices/system/clocksource/clocksource0/available_clocksource:tsc hpet acpi_pm 
> /sys/devices/system/clocksource/clocksource0/current_clocksource:tsc
> 



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