Re: effect of lower store_avg_obj_size setting

Geoff Nordli wrote:
>
> Why does reducing the size of the lower store_avg_obj_size setting
> get rid of the error "FATAL: file_map_allocate: Exceeded filemap limit".

Upon startup Squid allocates a static bitmap for keeping track of which
cache_dir files are being in use. The size of this bitmap is determined
by the cache_dir size and store_avg_obj_size.

> I would think that if you have enough cache (100MB) you still have
> 7700 objects to use with the default of 13K store_avg_size.

Yes, or actually 15000 (the limit is twice what Squid estimates based on
store_avg_obj_size), assuming you are using a recent version of Squid.

Most Squid 1.X versions had 20KB as default store_avg_obj_size and no
margin, which was a major pain for some people, as the real life average
object size dended to be 13KB.. Nowdays people usually only get this
error if they have manually changed store_avg_obj_size to a higher
value.

> Doesn't squid clean up its old entries when it starts to get full.

It does, but sometimes it has some trouble to keep up if the traffic
rate is high.

> I would think having less available objects would just make your
> caching less efficient.

???

> I guess I just want to know if I reduce the size of the store_avg_size
> paramater the same error message isn't going to come back.

If the error is that the actual average object size is much less then
yes.

> BTW can I safely delete the store.log file.

Yes, or turn if off completely.

squid.conf:
cache_store_log none

store.log can be regarded as a debug log. It is useful when you
experiment with refresh patterns or look into why a page is or isn't
cached, but it is of wery limited use in day-to-day use.

--
Henrik Nordstrom
Spare time Squid hacker