on linux: only one cpu in use?

[Sascha Ottolski]

Am Montag 29 September 2008 14:12:16 schrieb Tollef Fog Heen:
> ]] Sascha Ottolski
>
> | Am Montag 15 September 2008 16:16:33 schrieb Tollef Fog Heen:
> | > ]] Sascha Ottolski
> | >
> | > | it's debian etch with the stock 2.6.18 kernel. performance is
> | > | ok, beside the fact that the load climbs up when the cache is
> | > | about 40-50 % full (with a 517GB cache file); below 40 % the
> | > | load stays below 3, but after that level it rises to over 7 and
> | > | even 10 at peak times. the response times are still good,
> | > | though.
> | >
> | > Is this with the mmap or the malloc backend?
> |
> | well, as the man page says about malloc "Not recommended for
> | production use.", I use the file backend :-)
>
> Indeed.  Fixed that just now.  It seems like newer kernels has some
> performance problems we are tickling.  I haven't had the time to
> track down which commit breaks us, but it's fairly noticeable on busy
> sites.
>
> | In case it matters, it's with trunk r2640.
>
> This is fairly old, though.

I will test the current version soon. What would be the advice when 
giving the malloc backend a try? 

We run varnish on a 32 GB machine with about the same amout of swap, and 
use up to 517 GB as swap file (experimenting with smaller cache files 
to see if it changes load or response time, but so far couldn't really 
see a difference).

The wiki advices to limit the malloc to less then swap space, which 
would be probably way to low for our needs. Should add a big swapfile?


Thanks,

Sascha