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From "Mohit Anchlia" <mohitanch...@gmail.com>
Subject Re: [users@httpd] High load, low CPU and processes in state "devfs"
Date Mon, 16 Jun 2008 00:07:57 GMT
You'll need to analyze this data with what you are seeing on this system. I
suggest you get sar like tool. Look at http://www.googlebit.com/bsdsar/ or
see this post too
http://groups.google.com/group/sol.lists.freebsd.questions/browse_thread/thread/b999f095612e59bd/257ddbadf0c9ec71?hl=en&lnk=st&q=FreeBSD+sar#257ddbadf0c9ec71

Or ask you system admin. You need to look at it very closely.

On Sat, Jun 14, 2008 at 10:23 AM, Stut <stuttle@gmail.com> wrote:

> Thanks Mohit. Shortly after you sent this last night I enabled system
> accounting. There's now a fair amount of data in the output but I'm not
> really sure where to find the disk wait times...
>
> root@harold:~# sa
>   41065    44351.99re      428.71cp       11avio      823k
>    8678    33375.24re      418.23cp       34avio      496k   httpd*
>    2469       51.19re        4.79cp        2avio      767k   convert
>    1513     1180.51re        2.69cp       48avio     4929k   php
>    2469       56.01re        2.59cp        2avio     1312k   composite
>     590     3945.74re        0.09cp        5avio     6182k   smtp
>     624      152.45re        0.09cp        0avio   196079k   perl*
>      46      468.10re        0.08cp      691avio      574k   cleanup
>    1170       10.05re        0.08cp       11avio   107305k   rateup
>      47      388.52re        0.03cp      190avio     1054k   pickup
>     743      240.80re        0.02cp        0avio    27976k
> trivial-rewrite
>   10443     1319.75re        0.00cp        0avio 26333351k   sh
>     154      305.90re        0.00cp       24avio    44750k   bounce
>    4454      101.21re        0.00cp        0avio  1753042k   sendmail
>    4454       52.77re        0.00cp        7avio  2748826k   postdrop
>       2        1.00re        0.00cp        0avio     3136k   top
>       9     1278.02re        0.00cp        2avio    32944k   ***other
>     389       13.73re        0.00cp        0avio   908587k   ps
>       2        0.01re        0.00cp        6avio      981k   sa
>      24       80.90re        0.00cp        0avio    60224k   scache
>       9       35.12re        0.00cp        0avio    12700k   anvil
>      78        0.28re        0.00cp        0avio   198900k   atrun
>     623     1043.23re        0.00cp        0avio   959100k   cron*
>      39        1.24re        0.00cp        2avio   112100k   dd
>      27       52.78re        0.00cp        0avio   109600k   error
>      65      114.24re        0.00cp        0avio   298000k   flush
>    1165       41.51re        0.00cp        0avio  4475200k   grep
>      40        0.14re        0.00cp        0avio    60000k   jot
>     279        1.16re        0.00cp        3avio   971600k   mv
>       7        0.31re        0.00cp        3avio     7200k   newsyslog
>      13        1.68re        0.00cp        0avio    42500k   proxymap
>      12       23.78re        0.00cp        0avio    78800k   smtpd
>      40        0.16re        0.00cp        2avio   194800k   unlink
>     388       14.47re        0.00cp        0avio  1219700k   wc
>
> Any help would be appreciated. Thanks.
>
> -Stut
>
>
> On 14 Jun 2008, at 00:43, Mohit Anchlia wrote:
>
>  try "sa"
>>
>> On 6/13/08, Stut <stuttle@gmail.com> wrote: On 13 Jun 2008, at 23:38,
>> Mohit Anchlia wrote:
>> look at "sar" output and see the wait times on the disk is more than the
>> service time.
>>
>> That command doesn't seem to exist on FreeBSD. Do you know if there's an
>> equivalent command?
>>
>> -Stut
>>
>>
>> On 6/13/08, Stut <stuttle@gmail.com> wrote:
>>
>> 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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>>
>
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