On Tue, Sep 17, 2013 at 02:59:24PM +0800, Bob Liu wrote: > Hi Krzysztof, > > On 09/11/2013 04:58 PM, Krzysztof Kozlowski wrote: > > Hi, > > > > Currently zbud pages are not movable and they cannot be allocated from CMA > > (Contiguous Memory Allocator) region. These patches add migration of zbud pages. > > > > I agree that the migration of zbud pages is important so that system > will not enter order-0 page fragmentation and can be helpful for page > compaction/huge pages etc.. > > But after I looked at the [patch 4/5], I found it will make zbud very > complicated. > I'd prefer to add this migration feature later until current version > zswap/zbud becomes better enough and more stable. I agree with this. We are also looking to add zsmalloc as an option too. It would be nice to come up with a solution that worked for both (any) allocator that zswap used. > > Mel mentioned several problems about zswap/zbud in thread "[PATCH v6 > 0/5] zram/zsmalloc promotion". > > Like "it's clunky as hell and the layering between zswap and zbud is > twisty" and "I think I brought up its stalling behaviour during review > when it was being merged. It would have been preferable if writeback > could be initiated in batches and then waited on at the very least.. > It's worse that it uses _swap_writepage directly instead of going > through a writepage ops. It would have been better if zbud pages > existed on the LRU and written back with an address space ops and > properly handled asynchonous writeback." Yes, the laying in zswap vs zbud is wonky and should be addressed before adding new layers. > > So I think it would be better if we can address those issues at first > and it would be easier to address these issues before adding more new > features. Welcome any ideas. Agreed. Seth -- 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>