High CPU system usage

Ugo Bellavance ugob at CAMO-ROUTE.COM
Thu Aug 25 21:35:10 IST 2005

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Glenn Steen wrote:
> On 25/08/05, Ugo Bellavance <ugob at camo-route.com> wrote:
>>Glenn Steen wrote:
>>>BTW, as one can see from the "new style" listing, you get hit a fair
>>>bit on "/" too, perhaps something to look at...
>>>If you decide to revert to ext2, take care with "/" and your initrd.
>>>But you knew that:-).
>>I'm wondering what is reading/writing on '/'.
> I was going to say "/tmp", but you have that separate too.... so this
> might actually be your "clincher".Since it's mostly writing you might
> be able to find out what gets written through the atime bit... some
> "intelligent" find or just browsing with an appropriate ls. lsof might
> also give a clue or two.
>>Another thing that makes me wonder is the amount of idle CPU.  I just
>>logged in as my server had a high load and I saw that even with many
>>MailScanner processes running and using CPU, there was often significant
>>Idle %. (10-30%).
> Well, although generally IO is CPU-bound, you could see this if you
> were exhausting your RAID-controllers write-cache.... I'm not too
> familiar with the one you've got there (more used to SMARTs at the low
> end and Clariions/FC on the "high" end), but if you have your cache
> watermark levels wrong (for the IO patterns you see) you might see
> rather "choppy" behaviour.... if you have such at all.
> Also, write-cache mirroring can be a real performance killer. I
> usually try to live with that though, safety first and all that:-).
> Or it's something else altogether:-).
> What did the top show?

Many MailScanner and MailScanner-related processes (MailScanner, bdc,
fprot, etc...) at top (using most CPU time).  bind sometimes got in the
12-ish rank, maybe once in 2 minutes.  Nothing really weird to me.


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