Re: [squid-users] Cache_dir more than 10GB

From: Itzcak Pechtalt <>
Date: Sun, 12 Oct 2008 21:21:03 +0200


I reviewed Squid filemap code and it's clear that in some cases
a large cache will have high CPU load.
filemap.c function file_map_create function starts with 2^13 elements
and expands element number only after the list is full.
So for example if cached objects are always slightly below 2^23 and bitmap
size is 2^23 it will take a lot of CPU to find next free bit.


On Mon, Oct 6, 2008 at 1:05 PM, Henrik Nordstrom
<> wrote:
> On sön, 2008-10-05 at 16:38 +0200, Itzcak Pechtalt wrote:
>> When Squid reach several millions of objects per cache dir, it start
>> to be very CPU consumer, becuae every insertion and deletion of object
>> takes long time.
> Mine don't.
>> On my Squid 80-100GB had the CPU consumption effect.
> That's a fairly small cache.
> The biggest cache I have been running was in the 1.5TB range, split over
> a number of cache_dir, about 130GB each I think.
> But it is important you keep the number of objects per cache_dir well
> below 2^24. Preferably not more than 2^23.
> What I think is that you got bitten by something else than cache size..
> Regards
> Henrik
Received on Sun Oct 12 2008 - 19:21:06 MDT

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