Messages in this thread | | | Date | Fri, 07 Feb 2014 10:50:35 +0100 | From | Vlastimil Babka <> | Subject | Re: [PATCH 3/5] mm/compaction: change the timing to check to drop the spinlock |
| |
On 02/07/2014 06:08 AM, Joonsoo Kim wrote: > It is odd to drop the spinlock when we scan (SWAP_CLUSTER_MAX - 1) th pfn > page. This may results in below situation while isolating migratepage. > > 1. try isolate 0x0 ~ 0x200 pfn pages. > 2. When low_pfn is 0x1ff, ((low_pfn+1) % SWAP_CLUSTER_MAX) == 0, so drop > the spinlock. > 3. Then, to complete isolating, retry to aquire the lock. > > I think that it is better to use SWAP_CLUSTER_MAX th pfn for checking > the criteria about dropping the lock. This has no harm 0x0 pfn, because, > at this time, locked variable would be false. > > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> diff --git a/mm/compaction.c b/mm/compaction.c > index 0d821a2..b1ba297 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -481,7 +481,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > cond_resched(); > for (; low_pfn < end_pfn; low_pfn++) { > /* give a chance to irqs before checking need_resched() */ > - if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) { > + if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) { > if (should_release_lock(&zone->lru_lock)) { > spin_unlock_irqrestore(&zone->lru_lock, flags); > locked = false; >
| |