Re: PROBLEM: zone_reclaim is hanging high priority real time user pthreads

[Mel Gorman <mgorman@suse.de>]

On Fri, May 27, 2011 at 01:22:42PM +0200, Bertil Engelholm wrote:
> Thanx for the response. Since a few days back we have tried disabling the 
> zone reclaim and the system behaves much better so that seems to be the
> short term solution we'll go for.

Good news.

> I also assume that if you have real time pthreads that are sensitive to 
> stalls you might have to disable zone reclaim also in later kernels
> even though the zone reclaim implementation have been radically improved.
> 

It'd be one possibility. However, I understand that at least one person
is considering adding an additional level of watermarks that is
dependant on the number of real-time threads in the system and their
expected usage. The idea would be that latency sensitive applications
would be allowed to use a number of pages between two watermarks were
other users would wake kswapd or enter direct reclaim. I don't know
where that currently stands though.

Thanks.

-- 
Mel Gorman
SUSE Labs