Re: [squid-users] Performance impact of a higher cache_mem setting

To use highly technical terms: "not a whole lot".

cache_mem can make a slight performance difference when the difference
is between the default of 8MB and something higher, like 64MB. But in
your case, I'd say 256-384MB is about as good as it's going to get. In
fact, you're likely to see somewhat decreasing performance at some point
because your OS can actually bring objects back into memory from disk
and keep them there while Squid can only keep new (newly pulled from the
network) objects in its "hot object" memory cache.

This also depends on the memory performance of the underlying OS and its
memory efficiency. In some rare cases, Squid might be much more
efficient in its memory usage than the OS. FreeBSD is almost certainly
not one of these cases (though I don't have personal experience to back
this assertion up).

To be more precise about it, I've done some benchmarking of this option
in the past, and the difference between 8MB and 64MB on a 512MB machine
was something along the lines of 4% in favor of 64MB. I didn't see any
statistically significant difference when the value was raised to 128MB.

francisv@dagupan.com wrote:

> Hi,
>
> What's the performance impact of a higher cache_mem setting? Right now, it's
> set at 256MB. The total cache_dir size is 50,867 MB (51GB) spread over 3
> disks. This machine is part of the WCCP cache farm so we have a lot of users
> connected simultaneously. We have 1.5 GB of RAM on the server running
> FreeBSD 4.3-STABLE and Squid 2.4STABLE1.

                                   --
                      Joe Cooper <joe@swelltech.com>
                  Affordable Web Caching Proxy Appliances
                         http://www.swelltech.com
Received on Sun Aug 26 2001 - 22:40:47 MDT