Re: [Lse-tech] [PATCH 1/2] node affine NUMA scheduler

From: Erich Focht (
Date: Sun Sep 22 2002 - 05:35:13 EST

On Saturday 21 September 2002 18:46, Martin J. Bligh wrote:
> > Hmmm .... well I ran the One True Benchmark (tm). The patch
> > *increased* my kernel compile time from about 20s to about 28s.
> > Not sure I like that idea ;-) Anything you'd like tweaked, or
> > more info? Both user and system time were up ... I'll grab a
> > profile of kernel stuff.
> From the below, I'd suggest you're getting pages off the wrong
> nodes: do_anonymous_page is page zeroing, and rmqueue the buddy
> allocator. Are you sure the current->node thing is getting set
> correctly? I'll try backing out your alloc_pages tweaking, and
> see what happens.

Could you please check in dmesg whether the CPU pools are initialised
correctly? Maybe something goes wrong for your platform.

The node_distance is most probably non-optimal for NUMAQ, that might
need some tuning. The default is set for maximum 8 nodes, nodes 1-4
and 5-8 being in separate supernodes, with the latency ratios 1:1.5:2.

You could use the attached patch for getting an idea about the load
distribution. It's a quick&dirty hack which creates files called
/proc/sched/load/rqNN :load of RQs, including info on tasks not running
                        on their homenode
/proc/sched/history/ilbNN : history of last 25 initial load balancing
                            decisions for runqueue NN
/proc/sched/history/lbNN : last 25 load balancing decisions on rq NN.

It should be possible to find the reason for the poor performance by
looking at the nr_homenode entries in /proc/sched/load/rqNN.

best regards,

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