Re: Buffer Cache v's Memory Pool's

From: Alex Rousskov <>
Date: Sat, 4 Jul 1998 12:45:25 -0600 (MDT)

On Sat, 4 Jul 1998, Peter Marelas wrote:

> Has anyone done any detailed analysis which compares a file systems
> buffer cache versus squid memory pool's to cache recent objects?
> i.e. which provides better performance
> At the moment im utilising memory pool's and tossing up whether i should
> try buffer cache instead.

Be sure you use recent version of 1.1 or 1.2. There was an old bug that
prevented hot memory buffer from working efficiently. I have no information
if the fixed version performs much better though. It might be the case that
hot memory buffer managed by LRU is a bad idea for proxies in general.

Some memory buffer is needed for intransit objects, of course.

As for the FS cache, I suspect it is important for two things:
        1) caching i-nodes for subdirectories to speedup access to files
        2) buffering swap-out requests (we usually see swap-out requests
           being much faster than swap-ins)
Theoretically, you can estimate the amount of kernel memory needed to achieve
these two goals and tune your kernel respectfully.

I am not aware of any detailed studies of this tuning tradeoff. Please keep
us posted if you find something interesting.

Thank you,


P.S. When talking about memory pools, I assume you are talking about
cache_mem, not mem_pools. :)
Received on Sat Jul 04 1998 - 11:46:39 MDT

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