Con Kolivas wrote:
> I set out to find how the hyper-thread schedulers would affect the all
> important kernel compile benchmark on machines that most of us are likely to
> encounter soon. The single processor HT machine.
>
> Usual benchmark precautions taken; best of five runs (curiously the fastest
> was almost always the second run). Although for confirmation I really did
> this twice.
>
> Tested a kernel compile with make vmlinux, make -j2 and make -j8.
>
> make vmlinux - tests to ensure the sequential single threaded make doesn't
> suffer as a result of these tweaks
>
> make -j2 vmlinux - tests to see how well wasted idle time is avoided
>
> make -j8 vmlinux - maximum throughput test (4x nr_cpus seems to be ceiling for
> this).
>
> Hardware: P4 HT 3.066
>
> Legend:
> UP - Uniprocessor 2.6.0-test11 kernel
> SMP - SMP kernel
> C1 - With Ingo's C1 hyperthread patch
> w26 - With Nick's w26 sched-rollup (hyperthread included)
>
> make vmlinux
> kernel time
> UP 65.96
> SMP 65.80
> C1 66.54
> w26 66.25
>
> I was concerned this might happen and indeed the sequential single threaded
> compile is slightly worse on both HT schedulers. (1)
>
> make -j2 vmlinux
> kernel time
> UP 65.17
> SMP 57.77
> C1 66.01
> w26 57.94
>
> Shows the smp kernel nicely utilises HT whereas the UP kernel doesn't. The C1
> result was very repeatable and I was unable to get it lower than this.(2)
>
> make -j8 vmlinux
> kernel time
> UP 65.00
> SMP 57.85
> C1 58.25
> w26 57.94
If you could make one more test, do the compile with -pipe set in the
top level Makefile. I don't have play access to a HT uni, the only
machines available to me at the moment are SMP and production at that.
I did try it just for grins on a non-HT uni and saw this:
opt real user sys idle
-j1 406.2 308.1 19.0 79.1
-j1 -pipe 398.6 308.2 19.0 71.4
-j3 391.6 308.3 19.0 64.3
-j3 -pipe 388.7 308.4 19.0 61.3
P4-2.4MHz, 256MB, compiling 2.5.47-ac6 with just "make." Using -pipe
*may* allow both siblings to cooperate better.
I assume that CPU affinity should apply to all siblings in a package?
--
bill davidsen <davidsen _at_ tmr.com>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
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