Gunnar,
us = user (things like MySQL/PHP/Apache)
sy = system (memory management / swap space / threading / kernel
processes and so on)
ni = nice (apps running only when nothing else needs the resource)
id = idle (extra cpu cycles being wasted)
wa = wait state (io wait for disk/network/memory)
hi & si - interrupts
Generally acceptable load should be < #processors (so in your case 2
is okay - machine is performing well - 4 somethings being over
utilized somewhere)
Also in top 100% = 100% of one processor, so in a dual processor (or
core) setup, you can actually go to 200%
Your userland apps are taking up 61.3 + 57.0 (118.3% of 200% or 59%
overall) of system resources.
Your system processes are taking up 66.2% (of 200% or 33% overall)
and it's leaving about 14% (of 200% - so 7% overall) of the system idle.
The remainders are I/O waits etc (your numbers look pretty good there,
but IO wait can spike and so may be misleading without using other
tools.
You may be encountering a thrashing problem with the amount of memory
left or any number of things, but I would look at memory use on this
box, because your load is pretty high and your performance is
suffering if it's staying there. Your memory is at about 92% utilized
too... while 91Mb seems like a lot of memory - it's easily consumed by
a couple of large queries, sorts and so on which then goes right to
disk swapping for virtual memory - never good for performance. It
might also be impacted by IO and you just can't see it in the one
slice of top we have here. If that number spikes up to 5% and then
falls back down - it might be time spent going to disk with temp
tables etc.
Also turn on slow query logging (yes, I know it's another performance
hit) and see if there is one query that's particularly problematic,
perhaps optimizing the indexes etc on the table might help with the
performance.
Also, make sure your HD's aren't full... that will kill performance
very quickly if the needed disk space isn't there.
Erik
On Jan 3, 2008, at 3:44 PM, Gunnar R. wrote:
Hello,
Thanks. I read the document, but unfortunately it didn't tell me
anything
new..
One of the things I am a bit confused about is:
top - 22:08:12 up 6 days, 7:23, 1 user, load average: 4.36, 3.30,
2.84
Tasks: 134 total, 1 running, 133 sleeping, 0 stopped, 0 zombie
Cpu0 : 61.3% us, 29.1% sy, 0.0% ni, 7.9% id, 0.7% wa, 0.3% hi,
0.7% si
Cpu1 : 57.0% us, 37.1% sy, 0.0% ni, 6.0% id, 0.0% wa, 0.0% hi,
0.0% si
Mem: 1034280k total, 942780k used, 91500k free, 34252k
buffers
Swap: 2031608k total, 104k used, 2031504k free, 278788k
cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2410 mysql 15 0 470m 310m 4464 S 99.9 30.8 4200:25 mysqld
How come the CPUs can have idle time even though mysqld is running at
99.9%, AND there's a processor queue (4.36)?
Cheers,
Gunnar R.
On ons, januar 2, 2008, 13:07, Andrew Braithwaite wrote:
Hi,
If you can follow this document:
http://www.ufsdump.org/papers/uuasc-june-2006.pdf
You should be able to figure out what's happening.
Cheers,
Andrew
-----Original Message-----
From: Gunnar R. [mailto:[EMAIL PROTECTED]
Sent: Tue, 01 January 2008 23:31
To: mysql@lists.mysql.com
Subject: Performance problem - MySQL at 99.9% CPU
Hello,
I am running a community site mainly based on phpBB. It has about
9.300
registered users, 650.000 posts and about 200.000 visitors/month (12
mill
"hits"). The SQL database is about 700MB.
It's all running on a couple of years old Dell box with two P4 Xeon
1.7Ghz
CPUs, 1GB of RAMBUS memory and SCSI disks, with Linux and Apache.
The last year the server has been having huge performance problems,
and
MySQL (5.0.45) seems to be the problem. It's almost constantly
running
at
99.9% CPU ("measured" using 'top').
I know the hardware isn't too hot, but either way I am a bit
confused by
the
fact that I can't seem to get MySQL to run smoothly. Is this just too
big a
database for this kind of box, or could this be a configuration
issue?
I am thinking about buying a new dual core box (with IDE disks?),
but I
have
to make sure this really is a hardware issue before I spend
thousands of
bucks.
Any help will be hugely appreciated!
Cheers,
Gunnar
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