How to debug high system load?

[Suvayu Ali]

Hi Paweł and Heinz,

On Sun, Jul 15, 2012 at 03:55:45PM +0200, Paweł Brodacki wrote:
> 2012/7/15 suvayu ali <fatkasuvayu+linux at gmail.com>:
> > Hi Heinz,
> >
> > Sorry for the late response.
> >
> > On Thu, Jul 12, 2012 at 7:31 PM, Heinz Diehl <htd at fritha.org> wrote:
> >> On 12.07.2012, Suvayu Ali wrote:
> (...)
> >> If you're using cfq as your scheduler, try this in rc.local:
> >>
> >> echo "32" > /sys/block/sda/queue/iosched/quantum
> >> echo "0" > /sys/block/sda/queue/iosched/slice_idle
> >> echo "1" > /sys/block/sda/queue/iosched/low_latency
> >> echo "51200" > /sys/block/sda/queue/nr_requests
> >>
> >> Together with this in /etc/sysctl.conf:
> >>
> >> vm.dirty_ratio = 10
> >> vm.dirty_background_ratio = 5
> >>
> >
> > I tend not to try things that I don't understand. Could please outline
> > briefly what the above suggestions do? I would like to understand before
> > I try them out.
> >
> > Thanks,
> >
> 
> When vm.dirty_ratio percent of total system memory is taken up by
> dirty pages (data waiting to be saved to disk), the process which is
> generating disk writes will itself start writing out dirty data. It
> means, that program will be made to stop using system buffers to hide
> cost of writes, and to write the data to the disk.
> 
> When vm.dirty_background_ratio of total system memory is taken up by
> dirty pages, the pdflush background writeback daemon will start
> writing out dirty data.
> 
> If you keep these lower, the system will try to prevent accumulation
> of large amounts of data to write. Therefore, when sync comes, you
> will not have to wait for the accumulated data to be written to disk.
> 
> vm tunables are explained here:
> https://www.kernel.org/doc/Documentation/sysctl/vm.txt.

Thanks for the nice explanation. But sadly this doesn't help either.
Earlier the load average on login would be ~ 1-1.5. With these changes,
it starts at ~ 2 and after about 5 minutes settles to ~ 1-1.2. For
example now my laptop has been running for 50 minutes and load is
hovering over 1. :(

-- 
Suvayu

Open source is the future. It sets us free.