Re: [squid-users] investigate squid eating 100% CPU

[…]

> client<->squid : 31Mbps.

[…]

> Squid<->server : 28Mbps
>
> Total: 59Mbps.
>
> Which is slightly higher than the known "good" performance limit for Squid-3.1. Which is up to ~50Mbps, tuning both in Squid and the system can reach around 100Mbps IIRC. But that sort of numbers you are looking at specific traffic types as well.

Ah ! Thank you very much for this valuable figures.
50Mb/s is not what I was really hoping/expecting. I was naively thinking that Squid can handle multi 100Mb/s out of the box (at least with no ACLs, and other fancy stuff)
We have 2x100Mb/s Internet connections in front of this proxy.

>> select_loops = 2316.561716/sec
> <snip>
>> syscalls.sock.reads = 1316.883520/sec
>> syscalls.sock.writes = 1770.096831/sec
>
> It looks like sending and receiving data in ~2KB chunks, just over one packet per cycle.
>
>> syscalls.sock.recvfroms = 58.203913/sec
>> syscalls.sock.sendtos = 30.974986/sec
>> cpu_time = 117.934176 seconds
>> wall_time = 300.048557 seconds
>> cpu_usage = 39.305030%
>
> CPU usage at 40%.
>
> Squid-3.1 does use around 30% CPU to push data at line rate, which is what this set of counters seems to be showing. We have done a bunch of work aimed at improving things all over Squid in the more recent releases, if you want to assist the developers tracking this down please upgrade to the latest release before delving too deeply into the analysis as all fixes need to go in through 3.HEAD anyway and you maybe repeating already done work (only might there is still CPU issues hiding in the latest development code).

Point taken, I'll do that.

> What do things look like when its at or close to 100% CPU?

Basically, some users complain about browsing slowing down. But the main complaint is about download speeds of "large" files (~50MB -> GB) (but this can be explaind by the natural limits of Squid)

> Also any sign of the OS swapping virtual memory when the CPU climbs? that is a known performance killer for a number of reasons we can't fix easily.

Already checked this area, no swapping involved.

> Amos

Youssef
Received on Wed Mar 27 2013 - 17:41:05 MDT