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SubjectRe: [patch] sched-sync-2.5.69-A0
At 10:35 AM 5/19/2003 +0200, Ingo Molnar wrote:

>the attached patch fixes the scheduler's sync-wakeup code to be consistent
>on UP as well.
>
>Right now there's a behavioral difference between an UP kernel and an SMP
>kernel running on a UP box: sync wakeups (which are only activated on SMP)
>can cause a wakeup of a higher prio task, without preemption. On UP
>kernels this does not happen. This difference in wakeup behavior is bad.

Cool. That was the cause of some of the radical differences in behavior
between smp and up kernels. The sync wakeup in pipe wait for example was
the irman process load climbs through the roof problem, and it also affects
the ext3 concurrency problem if you have gcc using -pipe. See attached log.

-Mike [before]:# time ./irman
Response time measurements (milliseconds) for: 2.5.69
Load Max Min Avg Std. Dev.
NULL 0.142 0.009 0.011 0.002
MEMORY 107.040 0.010 0.021 0.996
FILE_IO 310.991 0.010 0.033 2.598
PROCESS 1021.873 0.010 0.053 5.625

real 3m32.588s
user 0m28.350s
sys 0m21.353s

[before]:# time make -j30 bzImage (ext3, gcc using -pipe)
real 2m32.142s
user 2m14.505s
sys 0m10.685s

[before]:# grep pswp /proc/vmstat
pswpin 1448
pswpout 2436

[after]:# time ./irman
Response time measurements (milliseconds) for: 2.5.69
Load Max Min Avg Std. Dev.
NULL 0.286 0.010 0.011 0.002
MEMORY 103.111 0.010 0.021 0.990
FILE_IO 306.151 0.010 0.033 2.578
PROCESS 359.072 0.010 0.033 0.687

real 2m23.548s
user 0m26.160s
sys 0m22.940s

[after]:# time make -j30 bzImage (ext3, gcc using -pipe)
real 2m35.018s
user 2m16.075s
sys 0m11.899s

[after]:# grep pswp /proc/vmstat
pswpin 19220
pswpout 33019
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