Re: Complete I/O starvation with 3ware raid on 2.6

[Jens Axboe <axboe@suse.de>]

On Thu, Sep 25 2003, Aaron Lehmann wrote:
> On Thu, Sep 25, 2003 at 07:13:32PM +1000, Nick Piggin wrote:
> > But the load average will be 11 because there are processes stuck in the
> > kernel somewhere in D state. Have a look for them. They might be things
> > like pdflush, kswapd, scsi_*, etc.
> 
> They're pdflush and kjournald. I don't have sysrq support compiled in
> at the moment.
> 
> I've noticed the problem does not occur when the raid can absorb data
> faster than the other drive can throw data at it. My naive mind is
> pretty sure that this is just an issue of way too much being queued
> for writing. If someone could tell me how to control this parameter,
> I'd definately give it a try [tomorrow]. All I've found on my own is
> #define TW_Q_LENGTH 256 in 3w-xxxx.h and am not sure if this is the
> right thing to change or safe to change.

That is the right define, try setting it to something low. 8, or maybe
even 4. Don't go below 3, though.

-- 
Jens Axboe