Re: Buffer Cache v's Cache_Mem (Was Memory Pool's)

From: Alex Rousskov <>
Date: Thu, 16 Jul 1998 01:09:00 -0600 (MDT)

On Thu, 16 Jul 1998, Peter Marelas wrote:

> One of the benefits of using the FS buffer cache is that a larger amount
> of memory is controlled by the OS, and therefore unlikely to utilise swap, while
> gaining maximum use of physical memory.
> To summarise, I am seeing better performance and stability by utilising
> FreeBSD's FS buffer cache, rather than Squid's object cache.

Well, I can see from your report that reducing cache_mem helped.

There are no hard numbers that say that FreeBSD's FS buffer cache works. In
other words, we can only speculate that OS is using the free memory for FS
cache. An alternative would be to suspect that Squid was paging too much in
the previous configuration. OR that there is a certain, possibly low,
threshold that FreeBSD must have for caching i-nodes and such, and everything
above that does not matter.

To get a definitive answer, one would need to increase cache_mem slowly from
min to max and collect a lot of Squid and OS measurements while doing so. A
lot of work..

Thanks for the numbers!

Received on Thu Jul 16 1998 - 00:10:12 MDT

This archive was generated by hypermail pre-2.1.9 : Tue Dec 09 2003 - 16:41:08 MST