performance scalability of a multi-core

Poul-Henning Kamp phk at
Wed Sep 9 18:30:28 CEST 2009

In message <4AA7AD33.1060801 at>, =?UTF-8?B?VsOhY2xhdiBCw61sZWs=?= writes:
>what are your experiences using varnish on multi CPU systems on
>my experience in Linux on 8core  is that varnish never gets more than
>20% of all CPUs, only vhen it is overloaded, then it takes all CPU ( but
>berformance drops).

That is pretty typical behaviour.

In general Varnish does not need much CPU, it needs only an average
of seven sytem calls for a cache hit (last I looked).

The problem is that when things pile up, for whatever reason, Varnish
sort of climbs the pile.

Various ideas have been floated, how to deal better with that, but
no really good idea has been found yet.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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