* Chen, Kenneth W <[email protected]> wrote:
> The cache size information on ia64 is already available at the finger
> tip. Here is a patch that I whipped up to set max_cache_size for ia64.
Ingo Molnar wrote on Monday, April 04, 2005 4:38 AM
> thanks - i've added this to my tree.
>
> i've attached the latest snapshot. There are a number of changes in the
> patch: firstly, i changed the direction of the iteration to go from
> small sizes to larger sizes, and i added a method to detect the maximum.
>
> Furthermore, i tweaked the test some more to make it both faster and
> more reliable, and i cleaned up the code. (e.g. now we migrate via the
> scheduler, not via on_each_cpu().) The default patch should print enough
> debug information as-is.
>
> I changed the workload too so potentially the detected values might be
> off from the ideal value on your box. The values detected on x86 are
> mostly unchanged, relative to previous patches.
Perhaps, I'm not getting the latest patch? It skipped measuring because
migration cost array is non-zero (initialized to -1LL):
[00] [01] [02] [03]
[00]: - 0.0(0) 0.0(0) 0.0(0)
[01]: 0.0(0) - 0.0(0) 0.0(0)
[02]: 0.0(0) 0.0(0) - 0.0(0)
[03]: 0.0(0) 0.0(0) 0.0(0) -
--------------------------------
| cacheflush times [1]: 0.0 (-1)
| calibration delay: 0 seconds
--------------------------------
Need this change? I bet you had that in your tree already.
--- ./kernel/sched.c.orig 2005-04-04 18:01:45.000000000 -0700
+++ ./kernel/sched.c 2005-04-04 18:21:41.000000000 -0700
@@ -5050,7 +5050,7 @@ void __devinit calibrate_migration_costs
/*
* Do we have the result cached already?
*/
- if (migration_cost[distance])
+ if (migration_cost[distance] != -1LL)
cost = migration_cost[distance];
else {
cost = measure_migration_cost(cpu1, cpu2);
Also, the cost calculation in measure_one() looks fishy to me in this version.
> + /*
> + * Dirty the working set:
> + */
> + t0 = sched_clock();
> + touch_cache(cache, size);
> + t1 = sched_clock();
> +
> + /*
> + * Migrate to the target CPU, dirty the L2 cache and access
> + * the shared buffer. (which represents the working set
> + * of a migrated task.)
> + */
> + mask = cpumask_of_cpu(target);
> + set_cpus_allowed(current, mask);
> + WARN_ON(smp_processor_id() != target);
> +
> + t2 = sched_clock();
> + touch_cache(cache, size);
> + t3 = sched_clock();
> +
> + cost = t2-t1 + t3-t2;
Typo here ??
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