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SubjectRe: percpu-2.5.63-bk5-1 (properly generated)
> On Sun, Mar 02, 2003 at 10:24:37AM -0800, Martin J. Bligh wrote:
>> Odd. I get nothing like that difference.
>> Kernbench-2: (make -j N vmlinux, where N = 2 x num_cpus)
>> Elapsed User System CPU
>> 2.5.63-mjb2 44.43 557.16 95.31 1467.83
>> 2.5.63-mjb2-pernode 44.21 556.92 95.16 1474.33
>> Kernbench-16: (make -j N vmlinux, where N = 16 x num_cpus)
>> Elapsed User System CPU
>> 2.5.63-mjb2 45.39 560.26 117.25 1492.33
>> 2.5.63-mjb2-pernode 44.78 560.24 112.20 1501.17
>> No difference for make -j32, definite improvement in the systime for -j256.
> Maybe your machine's running slow?
> AFAIK the machines we're using are identical, and mine sees:

No, I just started using a config file for kernbench that has every option
under the sun turned on ;-) Makes a longer test, and stabilises results.
(2.4.17). It's the difference between before and after runs that's going to
be interesting anyway.

> make -j bzImage > /dev/null 317.70s user 148.43s system 1295% cpu 35.984 total
> (yes, this is 5 off of 41s, apparently 1s measurement variations are typical)

make -j is going to spawn as many tasks as possible, creating a massive
forkbomb ... that might be behind the differences - your patch might make
more of a difference for huge amounts of context switching / cache thrash
(not necessarily a bad thing, I just want to find the cause).

> make -j36 bzImage > /dev/null 302.33s user 115.02s system 1284% cpu 32.492 total
> make -j38 bzImage > /dev/null 302.52s user 117.06s system 1300% cpu 32.258 total
> make -j40 bzImage > /dev/null 303.53s user 117.42s system 1305% cpu 32.251 total
> make -j44 bzImage > /dev/null 304.02s user 122.14s system 1299% cpu 32.792 total

How does that compare with and without your patch though?

Would be useful if you can grab a before and after profile, and see exactly
what it is that's getting thrashed that you're fixing (may just be everything).


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