Kris Kennaway wrote:
> Alexey Popov wrote:
>> Hi.
>>
>> Panagiotis Christias wrote:
>>>>>>> In the "good" case you are getting a much higher interrupt rate but
>>>>>>> with the data you provided I can't tell where from. You need to run
>>>>>>> vmstat -i at regular intervals (e.g. every 10 seconds for a minute)
>>>>>>> during the "good" and "bad" times, since it only provides counters
>>>>>>> and an average rate over the uptime of the system.
>>>>>> Now I'm running 10-process lighttpd and the problem became no so big.
>>>>>>
>>>>>> I collected interrupt stats and it shows no relation beetween
>>>>>> ionterrupts and slowdowns. Here is it:
>>>>>> http://83.167.98.162/gprof/intr-graph/
>>>>>>
>>>>>> Also I have similiar statistics on mutex profiling and it shows
>>>>>> there's no problem in mutexes.
>>>>>> http://83.167.98.162/gprof/mtx-graph/mtxgifnew/
>>>>>>
>>>>>> I have no idea what else to check.
>>>>> I don't know what this graph is showing me :) When precisely is the
>>>>> system behaving poorly?
>>> what is your RAID controller configuration (read ahead/cache/write
>>> policy)? I have seen weird/bogus numbers (~100% busy) reported by
>>> systat -v when read ahead was enabled on LSI/amr controllers.
>>
>>
>> **********************************************************************
>> Existing Logical Drive Information
>> By LSI Logic Corp.,USA
>>
>> **********************************************************************
>> [Note: For SATA-2, 4 and 6 channel controllers, please specify
>> Ch=0 Id=0..15 for specifying physical drive(Ch=channel,
>> Id=Target)]
>>
>>
>> Logical Drive : 0( Adapter: 0 ): Status: OPTIMAL
>> ---------------------------------------------------
>> SpanDepth :01 RaidLevel: 5 RdAhead : Adaptive Cache:
>> DirectIo
>> StripSz :064KB Stripes : 6 WrPolicy: WriteBack
>>
>> Logical Drive 0 : SpanLevel_0 Disks
>> Chnl Target StartBlock Blocks Physical Target Status
>> ---- ------ ---------- ------ ----------------------
>> 0 00 0x00000000 0x22ec0000 ONLINE
>> 0 01 0x00000000 0x22ec0000 ONLINE
>> 0 02 0x00000000 0x22ec0000 ONLINE
>> 0 03 0x00000000 0x22ec0000 ONLINE
>> 0 04 0x00000000 0x22ec0000 ONLINE
>> 0 05 0x00000000 0x22ec0000 ONLINE
>>
>> I tried to run with disabled Read-ahead, but it didn't help.
>
> I just ran into this myself, and apparently it can be caused by "Patrol
> Reads" where the adapter periodically scans the disks to look for media
> errors. You can turn this off using -stopPR with the megarc port.
>
> Kris
>
Oops, -disPR is the correct command to disable, -stopPR just halts a PR
event in progress.
Kris
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