On 07/21/2010 04:33 AM, Minchan Kim wrote: > On Fri, Jul 16, 2010 at 9:37 PM, Nitin Gupta <ngupta@xxxxxxxxxx> wrote: >> User can change (per-pool) memlimit using sysfs node: >> /sys/kernel/mm/zcache/pool<id>/memlimit >> >> When memlimit is set to a value smaller than current >> number of pages allocated for that pool, excess pages >> are now freed immediately instead of waiting for get/ >> flush for these pages. >> >> Currently, victim page selection is essentially random. >> Automatic cache resizing and better page replacement >> policies will be implemented later. > > Okay. I know this isn't end. I just want to give a concern before you end up. > I don't know how you implement reclaim policy. > In current implementation, you use memlimit for determining when reclaim happen. > But i think we also should follow global reclaim policy of VM. > I means although memlimit doen't meet, we should reclaim zcache if > system has a trouble to reclaim memory. Yes, we should have a way to do reclaim depending on system memory pressure and also when user explicitly wants so i.e. when memlimit is lowered manually. > AFAIK, cleancache doesn't give any hint for that. so we should > implement it in zcache itself. I think cleancache should be kept minimal so yes, all reclaim policies should go in zcache layer only. > At first glance, we can use shrink_slab or oom_notifier. But both > doesn't give any information of zone although global reclaim do it by > per-zone. > AFAIK, Nick try to implement zone-aware shrink slab. Also if we need > it, we can change oom_notifier with zone-aware oom_notifier. Now it > seems anyone doesn't use oom_notifier so I am not sure it's useful. > I don't think we need these notifiers as we can simply create a thread to monitor cache hit rate, system memory pressure etc. and shrink/expand the cache accordingly. Thanks for your comments. Nitin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>