Messages in this thread Patch in this message | | | From | KOSAKI Motohiro <> | Subject | Re: [RFC PATCH 1/2] vmscan don't isolate too many pages in a zone | Date | Thu, 9 Jul 2009 16:01:26 +0900 (JST) |
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Hi
> I tried the semaphore based concurrent direct reclaim throttling, and > get these numbers. The run time is normal 30s, but can sometimes go up > by many folds. It seems that there are more hidden problems..
Hmm.... I think I and you have different priority list. May I explain why Rik and decide to use half of LRU pages?
the system have 4GB (=1M pages) memory. my patch allow 1M/2/32=16384 threads. I agree this is very large and inefficient. However IOW this is very conservative. I believe it don't makes too strong restriction problem.
In the other hand, your patch's concurrent restriction is small constant value (=32). it can be more efficient and it also can makes regression. IOW it is more aggressive approach.
e.g. if the system have >100 CPU, my patch can get enough much reclaimer but your patch makes tons idle cpus.
And, To recall original issue tearch us this is rarely and a bit insane workload issue. Then, I priotize to
1. prevent unnecessary OOM 2. no regression to typical workload 3. msgctl11 performance
IOW, I don't think msgctl11 performance is so important. May I ask why do you think msgctl11 performance is so important?
> > --- linux.orig/mm/vmscan.c > +++ linux/mm/vmscan.c > @@ -1042,6 +1042,7 @@ static unsigned long shrink_inactive_lis > unsigned long nr_reclaimed = 0; > struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); > int lumpy_reclaim = 0; > + static struct semaphore direct_reclaim_sem = __SEMAPHORE_INITIALIZER(direct_reclaim_sem, 32); > > /* > * If we need a large contiguous chunk of memory, or have > @@ -1057,6 +1058,9 @@ static unsigned long shrink_inactive_lis > > pagevec_init(&pvec, 1); > > + if (!current_is_kswapd()) > + down(&direct_reclaim_sem); > + > lru_add_drain(); > spin_lock_irq(&zone->lru_lock); > do { > @@ -1173,6 +1177,10 @@ static unsigned long shrink_inactive_lis > done: > local_irq_enable(); > pagevec_release(&pvec); > + > + if (!current_is_kswapd()) > + up(&direct_reclaim_sem); > + > return nr_reclaimed; > }
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