Re: [squid-users] High cpu load with squid

On 19/11/10 00:47, Michał Prokopiuk wrote:
> Dnia Czwartek, 18.11.2010 o 11:18 Amos Jeffries napisał:
>
>> Okay. The obvious config reasons for slowness are gone. So the next
>> thing is to find out exactly what Squid is doing.
>>
>> * you can check with strace to see whats the thing taking out the CPU.
>
> Not possible, when I run strace load groving wery fast, and i can't do anything.
>

Pity. That can pinpoint straight to the CPU hog function most times.

>>
>> Has the box started using swap memory space now? That can drastically
>> slow downs Squids index lookups or buffering of information relayed.
>
> No, on server are about 2 gb free ram (cached).
>
>>
>> Is RAID still running trying to duplicate the random cache IO actions?
>
> No, i remove raid, and create two cache_dir:
>
> cache_dir aufs /var/spool/squid-cache/cache 10000 60 100
> cache_dir aufs /var/spool/squid-cache/sda6/cache 10000 60 100
>
>
>>
>> Have you noticed if the problem appears and lasts for around 2 hours,
>> then goes away? that would indicate your DNS TTL overrides forcing squid
>> to try the wrong IPs for some site. CDN hosted sites (eg akamai and
>> youtube) can change their IPs with no notice when there are routing
>> problems to work around.
>
> The problem appears about 30 min - 1 h. I have local dnscache.
>
> I have one new information - when i decrease maximum_object_size from 100M to 20 M, squid work for two days without any problem, and then squid again get a lot of cpu. With 100M maximum_object_size squit work stable only for first fiew hours.

Aha! a clue!

So anything show up if you grep your access.log for requests bigger than
20 MB?
Can you increase in steps and see if there is a fixed limit that causes it?

"debug_options ALL,0 20,2" may have some indication of whats going on
with objects storage.

Amos

-- 
Please be using
   Current Stable Squid 2.7.STABLE9 or 3.1.9
   Beta testers wanted for 3.2.0.3