Andrew Morton writes:
Con Kolivas <[email protected]> wrote:
Swap prefetching doesn't use very much cpu but spends a lot of time waiting on
disk in uninterruptible sleep. This means it won't get preempted often even at
a low nice level since it is seen as sleeping most of the time. We want to
minimise its cpu impact so yield where possible.
Signed-off-by: Con Kolivas <[email protected]>
---
mm/swap_prefetch.c | 1 +
1 file changed, 1 insertion(+)
Index: linux-2.6.15-ck5/mm/swap_prefetch.c
===================================================================
--- linux-2.6.15-ck5.orig/mm/swap_prefetch.c 2006-03-02 14:00:46.000000000 +1100
+++ linux-2.6.15-ck5/mm/swap_prefetch.c 2006-03-08 08:49:32.000000000 +1100
@@ -421,6 +421,7 @@ static enum trickle_return trickle_swap(
if (trickle_swap_cache_async(swp_entry, node) == TRICKLE_DELAY)
break;
+ yield();
}
if (sp_stat.prefetched_pages) {
yield() really sucks if there are a lot of runnable tasks. And the amount
of CPU which that thread uses isn't likely to matter anyway.
I think it'd be better to just not do this. Perhaps alter the thread's
static priority instead? Does the scheduler have a knob which can be used
to disable a tasks's dynamic priority boost heuristic?
We do have SCHED_BATCH but even that doesn't really have the desired effect.
I know how much yield sucks and I actually want it to suck as much as yield
does.
Cheers,
Con
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