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From Stut <stut...@gmail.com>
Subject Re: [users@httpd] High load, low CPU and processes in state "devfs"
Date Fri, 13 Jun 2008 22:10:57 GMT

On 13 Jun 2008, at 22:56, Dragon wrote:

> Stut wrote:
>> On 13 Jun 2008, at 22:37, Dragon wrote:
>>> Stut wrote:
>>>> Hi,
>>>>
>>>> I have a problem with one of the web servers I manage. It runs
>>>> FreeBSD
>>>> 6.2, Apache 2.2.8 and PHP 5.2.1. It runs a high-ish number of  
>>>> pre- fork
>>>> processes (usually around 240).
>>>>
>>>> What basically happens is that during our peak hours in the evening
>>>> the site becomes very slow as does everything on the server. The  
>>>> top
>>>> output shows nearly all httpd processes in the state "devfs" and  
>>>> the
>>>> load is jumping up over 10 but the CPU is 70% idle. There's  
>>>> plenty of
>>>> free memory, over 4GB, and lots of available disk space.
>>>>
>>>> While it's in this state all disk access is painfully slow. I've
>>>> checked all the drives and the RAID card status and everything
>>>> appears
>>>> to be fine. It also recovers itself after a few hours when the
>>>> traffic
>>>> dies down again.
>>>>
>>>> I've spent a lot of today Googling but can't find any reference to
>>>> this particular combination of symptoms. Does anyone have any  
>>>> ideas?
>>> ---------------- End original message. ---------------------
>>>
>>> It sounds to me like your system is waiting on disk resources (I am
>>> assuming that is what the devfs state is), it is very likely trying
>>> to use swap space.
>>>
>>> Now much memory does this system have?
>>>
>>> If it has insufficient memory to keep most things in RAM, it is
>>> going to use a lot of swap and that will slow things down
>>> considerably.
>>
>> Oh how I wish it were that simple...
>>
>> Mem: 1629M Active, 770M Inact, 392M Wired, 68K Cache, 214M Buf, 4791M
>> Free
>> Swap: 8192M Total, 8192M Free
>>
>> No swap in use, plenty of free memory.
> ---------------- End original message. ---------------------
>
> Well, I took my best shot on the info presented. I still think there  
> is something in the disk I/O path that is acting as a bottleneck.
>
> Sorry it isn't so easy, I have nothing else here. Wish I could help.

No worries, thanks for trying.

I agree that it's probably disk-related, but other than these symptoms  
I can't find anything wrong.

I'll see if the FreeBSD list can help.

-Stut

-- 
http://stut.net/

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