%cpu in system - squid performance in FreeBSD 5.3

[Jeff Behl]

As a follow up to the below (original message at the very bottom), I
installed a load balancer in front of the machines which terminates the
tcp connections from clients and opens up a few, persistent connections
to each server over which requests are pipelined.  In this scenario
everything is copasetic:

last pid:  3377;  load averages:  0.12,  0.09,  0.08
up 0+17:24:53  10:02:13
31 processes:  1 running, 30 sleeping
CPU states:  5.1% user,  0.0% nice,  1.8% system,  1.2% interrupt, 92.0%
idle
Mem: 75M Active, 187M Inact, 168M Wired, 40K Cache, 214M Buf, 1482M Free
Swap: 4069M Total, 4069M Free

  PID USERNAME PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU
COMMAND
  474 squid     96    0 68276K 62480K select 0  53:38 16.80% 16.80%
squid
  311 bind      20    0 10628K  6016K kserel 0  12:28  0.00%  0.00%
named



It's actually so good that one machine can now handle all traffic
(around 180 Mb/s) at < %50 cpu utilization.  Seems like something in the
network stack is responsible for the high %system cpu util...

jeff


-----Original Message-----
From: owner-freebsd-performance at freebsd.org
[mailto:owner-freebsd-performance at freebsd.org] On Behalf Of Jeff Behl
Sent: Tuesday, December 07, 2004 9:17 AM
To: Sean Chittenden
Cc: freebsd-performance at freebsd.org
Subject: Re: %cpu in system - squid performance in FreeBSD 5.3

I upgraded to STABLE but  most cpu time is still being spent in system.

This system is doing ~20Mb/s total with all content being grabbed out of
memory.  I see similar results when running MySQL (a lot of time being
spent in system)

Any ideas on what updates to be on the lookout for that might help with
this?  Am I right in guessing that this is a SMP issue and doesn't have
anything to do with AMD architecture?

thx



FreeBSD www2 5.3-STABLE FreeBSD 5.3-STABLE #2: Sun Dec  5 21:06:14 PST 
2004     root at www2.cdn.sjc:/usr/obj/usr/src/sys/SMP  amd64


last pid: 15702;  load averages:  0.15,  0.31,  0.31                up 
0+19:55:14  09:09:28
38 processes:  2 running, 36 sleeping
CPU states:  5.4% user,  0.0% nice, 12.7% system,  3.4% interrupt, 78.4%
idle
Mem: 163M Active, 284M Inact, 193M Wired, 72K Cache, 214M Buf, 1245M
Free
Swap: 4069M Total, 4069M Free

  PID USERNAME PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU
COMMAND
  486 squid     96    0 79820K 73996K CPU1   1 110:00 15.04% 15.04%
squid
  480 squid     96    0 75804K 70012K select 0 105:56 14.89% 14.89%
squid





Sean Chittenden wrote:

>> but the % system time can fluctuate up to 60 at times.  My question 
>> is if this is about the type of performance I could expect, or if 
>> people have seen better.
>
>
> I don't know about other people, but I suspect you're running into 
> lock contention.  Try using a post 5.3 snapshot (something from
> RELENG_5) since alc@ has set debug.mpsafevm=1, which lets many calls 
> to the VM run without GIANT, which I suspect is your problem and why 
> the system usage is all over the place.  -sc
>

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howdy,

I've got a dual proc AMD64 (2gHz) FreeBSD 5.3R system running two squid
processes (to take advantage of both CPUs). Each process is doing
around 195 req/s, and the total bandwidth is ~40Mb/s (gig nic via bge
driver). Squid is being used exclusively as a reverse proxy, with all
content being served out of memory (very little disk activity).

Top shows:

CPU states: 16.0% user, 0.0% nice, 42.7% system, 7.6% interrupt, 33.6%
idle
Mem: 898M Active, 569M Inact, 179M Wired, 214M Buf, 171M Free
Swap: 4069M Total, 4069M Free

PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU CPU COMMAND
14598 squid 108 0 463M 459M select 0 39.2H 59.96% 59.96% squid
14605 squid 105 0 421M 416M CPU0 1 38.4H 49.95% 49.95% squid

but the % system time can fluctuate up to 60 at times. My question is
if this is about the type of performance I could expect, or if people
have seen better. I was expecting to see much better performance,
seeing how everything is being served out of memory, but maybe I'm
asking too much? 400 reqs/s from RAM doesn't seem like much. Is this a
FreeBSD issue (anybody else with similar experience)? A majority of the
cpu time being spent in system would seem to indictate such. What is
all the system load? How can i tell?

Any help/pointers/remarks appreciated

thanks,
jeff