* Chuck Ebbert <[email protected]> wrote:
> Parent CPU 1, child CPU 0, using old code for lock
> CPU clocks: 2066947815
> Parent CPU 1, child CPU 0, using new code for lock
> CPU clocks: 2818166922
> Parent CPU 1, child CPU 0, using old code for lock
> CPU clocks: 5635093038
> Parent CPU 1, child CPU 0, using new code for lock
> CPU clocks: 5250078921
your numbers show that for the first box, there's a 36% net slowdown
resulting from the new code. On the other (older) box, there's a 7%
speedup from the new code.
i ran the code on two newer boxes, 2.4 and 3.4 GHz Xeons, on two sibling
CPUs sharing the same physical CPU and on two different CPUs as well:
HT non-siblings [Xeon 2.40GHz], 1% slowdown:
Parent CPU 2, child CPU 0, using old code for lock
CPU clocks: 6712771070
Parent CPU 2, child CPU 0, using new code for lock
CPU clocks: 6787556068
HT siblings [Xeon 2.40GHz], 14% speedup:
Parent CPU 1, child CPU 0, using old code for lock
CPU clocks: 3587124593
Parent CPU 1, child CPU 0, using new code for lock
CPU clocks: 3079647206
HT non-siblings [Xeon 3.40GHz], 3% speedup:
Parent CPU 2, child CPU 0, using old code for lock
CPU clocks: 8486900988
Parent CPU 2, child CPU 0, using new code for lock
CPU clocks: 8255818784
HT siblings [Xeon 3.40GHz], 1% slowdown:
Parent CPU 3, child CPU 0, using old code for lock
CPU clocks: 3684195488
Parent CPU 3, child CPU 0, using new code for lock
CPU clocks: 3739797320
but given that the code is a drastic slowdown on older boxes (and
results in higher memory bus traffic, which may slow down other CPUs
too, which effect isnt measured here), i dont think we should apply the
patch, just yet - up until the point it becomes a clear winner on new
CPUs.
(in fact the ping-pong effect should be worse if more than 2 CPUs
contend for the spinlock.)
could someone run the tests on a dual-core box too?
Ingo
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