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SubjectRe: breaking down the performance of D7 scheduler patch
> Rick broke the non HT parts of D7 out into patches 2,3,4,5 for us.
> This has been useful in all sorts of ways ...
> http://marc.theaimsgroup.com/?l=lse-tech&m=104436251927067&w=2
> (I'll attatch his patches here for convenience, they're small, and I don't
> trust the archives not to munge them).
>
> Below I've done two runs on each interesting combo (2 is a no-op).
> Overall results are a slight improvement in kernbench and a degredation
> in SDET. My impressions from the data below (16x NUMA-Q)
>
> 3 - gives a good boost to kernbench, marginal degreadation on SDET.
> 4 - doesn't do much.
> 5 - gives some degredation to kernebench, most of the degredation of SDET.
>
> Conclusion: 3 = good (mostly). 5 = bad.

Breaking patch 3 down starts to get ugly as they seem to interact.

key:

2.5.59 - virgin
2.5.59-sched2.5 - first part of patch 3 (below)
2.5.59-sched2.5-2 - ditto
2.5.59-sched3B - second part of patch 3 (below)
2.5.59-sched3B-2 - ditto
2.5.59-sched3 - patch 2 & 3
2.5.59-sched3-2 - patch 2 & 3

Kernbench-2: (make -j N vmlinux, where N = 2 x num_cpus)
Elapsed User System CPU
2.5.59 46.08 563.88 118.38 1480.00
2.5.59-sched2.5 46.39 567.53 117.39 1475.83
2.5.59-sched2.5-2 46.56 567.31 118.03 1471.50
2.5.59-sched3B 45.84 563.63 116.31 1482.67
2.5.59-sched3B-2 45.69 563.92 117.26 1490.50
2.5.59-sched3 46.12 567.52 115.82 1480.83
2.5.59-sched3-2 46.37 567.81 116.48 1475.00

Conclusion: looking at system times - part 1 doesn't make much difference,
part 2 makes small improvment, both parts together work well But part 2
alone is the only thing that improves elapsed times.

Kernbench-16: (make -j N vmlinux, where N = 16 x num_cpus)
Elapsed User System CPU
2.5.59 47.45 568.02 143.17 1498.17
2.5.59-sched2.5 46.90 570.21 135.39 1503.83
2.5.59-sched2.5-2 47.03 570.14 135.93 1500.67
2.5.59-sched3B 47.58 567.37 137.88 1481.83
2.5.59-sched3B-2 47.35 568.26 138.61 1492.50
2.5.59-sched3 47.59 573.48 139.78 1498.33
2.5.59-sched3-2 47.61 573.63 139.97 1498.17

Conclusion: systime - part 1 is best, part 2 also helps, but not so much.
Both together do a *little* bit worse than the either part alone.
Part 1 alone improves elapsed a little bit.

Patch 3:

--- sched-2.5.59-02/kernel/sched.c Tue Feb 4 00:30:05 2003
+++ sched-2.5.59-03/kernel/sched.c Tue Feb 4 00:31:43 2003
@@ -54,20 +54,19 @@
/*
* These are the 'tuning knobs' of the scheduler:
*
- * Minimum timeslice is 10 msecs, default timeslice is 150 msecs,
- * maximum timeslice is 300 msecs. Timeslices get refilled after
+ * Minimum timeslice is 10 msecs, default timeslice is 100 msecs,
+ * maximum timeslice is 200 msecs. Timeslices get refilled after
* they expire.
*/
#define MIN_TIMESLICE ( 10 * HZ / 1000)
-#define MAX_TIMESLICE (300 * HZ / 1000)
-#define CHILD_PENALTY 95
+#define MAX_TIMESLICE (200 * HZ / 1000)
+#define CHILD_PENALTY 50
#define PARENT_PENALTY 100
#define EXIT_WEIGHT 3

--------------------- BROKE IT HALF HERE --------------

#define PRIO_BONUS_RATIO 25
#define INTERACTIVE_DELTA 2
-#define MAX_SLEEP_AVG (2*HZ)
-#define STARVATION_LIMIT (2*HZ)
-#define NODE_THRESHOLD 125
+#define MAX_SLEEP_AVG (10*HZ)
+#define STARVATION_LIMIT (30*HZ)
/*
* If a task is 'interactive' then we reinsert it in the active
@@ -1035,9 +1034,9 @@
* increasing number of running tasks:
*/
#define EXPIRED_STARVING(rq) \
- ((rq)->expired_timestamp && \
+ (STARVATION_LIMIT && ((rq)->expired_timestamp && \
(jiffies - (rq)->expired_timestamp >= \
- STARVATION_LIMIT * ((rq)->nr_running) + 1))
+ STARVATION_LIMIT * ((rq)->nr_running) + 1)))

/*
* This function gets called by the timer code, with HZ frequency.

-
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