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
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