On Fri, Nov 23, 2012 at 9:31 PM, Ingo Molnar [off-list ref] wrote:

* Ingo Molnar [off-list ref] wrote:

quoted

* Alex Shi [off-list ref] wrote:

quoted

quoted

Those of you who would like to test all the latest patches are
welcome to pick up latest bits at tip:master:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master

I am wondering if it is a problem, but it still exists on HEAD: c418de93e39891
http://article.gmane.org/gmane.linux.kernel.mm/90131/match=compiled+with+name+pl+and+start+it+on+my

like when just start 4 pl tasks, often 3 were running on node
0, and 1 was running on node 1. The old balance will average
assign tasks to different node, different core.

This is "normal" in the sense that the current mainline
scheduler is (supposed to be) doing something similar: if the
node is still within capacity, then there's no reason to move
those threads.

OTOH, I think with NUMA balancing we indeed want to spread
them better, if those tasks do not share memory with each
other but use their own memory. If they share memory then they
should remain on the same node if possible.

I rewrite the little test case by assemble:
==
.text

    .global _start

_start:

do_nop:
        nop
        nop
        jmp do_nop
==
It reproduced the problem on latest tip/master, HEAD: 7cb989d0159a6f43104992f18
like for 4 above tasks running, 3 of them running on node 0, one
running on node 1.

If kernel can detect the LLC of CPU is allowed for tasks aggregate, it's a nice
feature. if not, the aggregate may cause more cache missing.

Could you please check tip:master with -v17:

  git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master

?

It should place your workload better than v16 did.

Note, you might be able to find other combinations of tasks that
are not scheduled NUMA-perfectly yet, as task group placement is
not exhaustive yet.

You might want to check which combination looks the weirdest to
you and report it, so I can fix any remaining placement
inefficiencies in order of importance.

Thanks,

        Ingo

-- 
Thanks
    Alex

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