[squid-users] Squid3: 100 % CPU load during object caching

[Amos Jeffries]

On 23/07/2015 11:29 p.m., Marcus Kool wrote:
> I am not sure if it is relevant, maybe it is:
> 
> I am developing an ICAP daemon and after the ICAP server sends a "100
> continue"
> Squid sends the object to the ICAP server in small chunks of varying sizes:
> 4095, 5813, 1448, 4344, 1448, 1448, 2896, etc.
> Note that the interval of receiving the chunks is 1/1000th of a second.
> It seems that Squid forwards the object to the ICAP server every time it
> receives
> one or a few TCP packets.
> 
> I have a suspicion that in the scenario of 100% CPU, large #write calls
> and low throughput a similar thing is happening:
> Squid physically stores a small part of the object many times, i.e.
> every time one or a few TCP packets arrive.

If testing with low traffic (one connection) that guess is correct.
Squid is so fast that it cycles through the whole
allocate-memory->read()->process->write()-to-icap cycle in under a
millisecond.

It takes a few dozen busy clients in parallel to slow Slow down enough
to increase the chunk sizes.


> 
> Amos, is there a debug setting that can confirm/reject this suspicion?

Not that I recall at the moment.

Amos