[asterisk-dev] possible zaptel problem with SMP and RAID1

[François Delawarde]

Hello,

I thought this mail would be more appropriate in this mailing list, if 
not sorry about it.

I've been having interrupt problems since I'm trying to use analog 
zaptel hardware (mainly openvox A400 and OPVXA1200) on two dual core 
machines (AMD64 X2, different motherboards and network cards) with 
software RAID1 in two SATA drives. These problems didn't occur on my 
previous setups without any RAID.

The problem appears to happen randomly, a few times per minute (or 
sometimes per 5 minutes), zttest utility drops to 60-90%, saying that I 
had too many interrupts (showing lines like "8192 samples in 7212 sample 
interval"). Along with that come an audible "bip" and some rare times a 
small cut in conversation, or a small bit of echo during a very short 
time. I'll add that a higher disk load (running dbench) appears to 
increase a little the frequence of those problems (but not totally sure).

zttool show no missed interrupts with watchdog option enable before 
compilation. No shared interrupts. No IDE drives (related to possible 
DMA problem). No frame buffer, console only server. Tried with all 
PREEMPT kernel options, all HZ options, with and without IRQ balance, 
trying SMP afinity to switch interrupts to another core, all without 
result, except for PREEMPT options that makes zttest constantly report 
99.975586% instead of 100% when there are no problems.

I'm no kernel expert, but since the only pattern I found in all tests 
seemed to be related to RAID, I was wondering if spinlocks disabling 
interrupts like RAID drivers seem to be doing in SMP configuration would 
be the cause of delaying of zaptel interrupts, leading to the kind of 
problems I have. Any idea on that?


For info, the problem occurred on these combinations of setups:
- OS: Debian etch (tested on sarge)
- Processors: two different AMD64 X2, one of each is in AM2 socket.
- Partitions: ext3 on RAID1 (tested with ext3 on LVM on RAID1 and ext3 
on Encrypted LVM on RAID1)
- Custom kernel 2.6.21.6 with IMQ and Layer 7 (tested with 2.6.18 and 
with/without these two patches, also tested with XEN kernel with 
horrible, but expected results).
- zaptel 1.4.3 (tried 1.2 series, and 1.4 since 1.4.1).
- a few services: DNS, DHCP, Samba, PHP/MySQL interface, astmanproxy 
(tested without any).

Worked well on:
- OS: Debian etch
- AMD64 Sempron
- Kernel 2.6.18 with IMQ and Layer 7
- No RAID
- zaptel 1.4 series
- same services as above

Thanks,
François.