>>>>> On Mon, 14 Mar 2005 15:16:46 +1100, Peter Chubb <[EMAIL PROTECTED]> said:
Peter> According to LMbench2 on a 2-way 900MHz Itanium 2:
Peter> Context switching 0K - times in microseconds - smaller is better
Peter> ----------------------------------------------------------------
Peter> OS 2p/0k 4p/0k 8p/0k
Peter> ctx swtch ctx swtch ctx swtch
Peter> ----------------------------- --------- --------- ---------
Peter> Linux 2.5.72 1.5700000 1.6200000 1.7700000
Peter> Linux 2.6.0 15.0600 8.6900000 8.8600000
Peter> Linux 2.6.11 17.1900 17.2100 10.5400
Peter> I have to go now, but I'll try to track this down tomorrow.
I have noticed the same a while ago. Someone from Intel (Ken, IIRC)
investigated and confirmed that it is due to a scheduler change.
Basically, the scheduler is now much more aggressive about
loading-balancing to an idle CPU. Try running LMbench as "taskset 1
make rerun" and you'll see the effect. This has resulted in a
discussion with Carl Staelin (co-author and current maintainer of
LMbench) as to how LMbench could control for such issues. It's not
finished yet, but hopefully a future version of LMbench3 will
(optionally) allow you to control the affinity of processes so you can
factor out scheduling effects if desired.
--david
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