On Mon, Jul 25, 2016 at 10:20:14AM +0100, Mel Gorman wrote: > On Mon, Jul 25, 2016 at 05:04:56PM +0900, Minchan Kim wrote: > > > @@ -1429,6 +1429,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, > > > continue; > > > } > > > > > > + /* Pages skipped do not contribute to scan */ > > > + scan++; > > > + > > > > As I mentioned in previous version, under irq-disabled-spin-lock, such > > unbounded operation would make the latency spike worse if there are > > lot of pages we should skip. > > > > Don't we take care it? > > It's not unbounded, it's bound by the size of the LRU list and it's not > going to be enough to trigger a warning. While the lock hold time may be > undesirable, unlocking it every SWAP_CLUSTER_MAX pages may increase overall > contention. There also is the question of whether skipped pages should be > temporarily putback before unlocking the LRU to avoid isolated pages being > unavailable for too long. It also cannot easily just return early without > prematurely triggering OOM due to a lack of progress. I didn't feel the > complexity was justified. I measured the lock holding time and it took max 96ms during 360M scanning with hackbench. It was very easy to reproduce with node-lru because it should skip too many pages. Given that my box is much faster than usual mobile CPU, it would take more time in embedded system. I think irq disable during 96ms would be worth to be fixed. Anyway, I'm done by that which I measured time by hand so it's up to you that whether you want to fix or leave as it is until someone reports it with more real workload. > > -- > Mel Gorman > SUSE Labs > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>