On Fri, Sep 12, 2014 at 01:05:11PM -0400, Dan Streetman wrote: > On Fri, Sep 12, 2014 at 1:46 AM, Minchan Kim <minchan@xxxxxxxxxx> wrote: > > On Thu, Sep 11, 2014 at 04:53:51PM -0400, Dan Streetman wrote: > >> Now that zswap can use zsmalloc as a storage pool via zpool, it will > >> try to shrink its zsmalloc zs_pool once it reaches its max_pool_percent > >> limit. These patches implement zsmalloc shrinking. The way the pool is > >> shrunk is by finding a zspage and reclaiming it, by evicting each of its > >> objects that is in use. > >> > >> Without these patches zswap, and any other future user of zpool/zsmalloc > >> that attempts to shrink the zpool/zs_pool, will only get errors and will > >> be unable to shrink its zpool/zs_pool. With the ability to shrink, zswap > >> can keep the most recent compressed pages in memory. > >> > >> Note that the design of zsmalloc makes it impossible to actually find the > >> LRU zspage, so each class and fullness group is searched in a round-robin > >> method to find the next zspage to reclaim. Each fullness group orders its > >> zspages in LRU order, so the oldest zspage is used for each fullness group. > >> > > > > 1. Pz, Cc Mel who was strong against zswap with zsmalloc. > > 2. I don't think LRU stuff should be in allocator layer. Exp, it's really > > hard to work well in zsmalloc design. > > I didn't add any LRU - the existing fullness group LRU ordering is > already there. And yes, the zsmalloc design prevents any real LRU I don't think It's not LRU for reclaiming but just simple linked list for finding free slot. > ordering, beyond per-fullness-group LRU ordering. Yes. > > > 3. If you want to add another writeback, make zswap writeback sane first. > > current implemenation(zswap store -> zbud reclaim -> zswap writeback, > > even) is really ugly. > > why what's wrong with that? how else can zbud/zsmalloc evict stored objects? You can refer Mel's suggestion for zswap/zsmalloc and writeback problem. http://www.spinics.net/lists/linux-mm/msg61601.html http://lkml.iu.edu//hypermail/linux/kernel/1304.1/04334.html I think LRU/writeback should be upper layer, not allocator itself. Please, don't force every allocator to implement it for only zswap. > > > 4. Don't make zsmalloc complicated without any data(benefit, regression) > > I will never ack if you don't give any number and real usecase. > > ok, i'll run performance tests then, but let me know if you see any > technical problems with any of the patches before then. > > thanks! > > > > >> --- > >> > >> This patch set applies to linux-next. > >> > >> Dan Streetman (10): > >> zsmalloc: fix init_zspage free obj linking > >> zsmalloc: add fullness group list for ZS_FULL zspages > >> zsmalloc: always update lru ordering of each zspage > >> zsmalloc: move zspage obj freeing to separate function > >> zsmalloc: add atomic index to find zspage to reclaim > >> zsmalloc: add zs_ops to zs_pool > >> zsmalloc: add obj_handle_is_free() > >> zsmalloc: add reclaim_zspage() > >> zsmalloc: add zs_shrink() > >> zsmalloc: implement zs_zpool_shrink() with zs_shrink() > >> > >> drivers/block/zram/zram_drv.c | 2 +- > >> include/linux/zsmalloc.h | 7 +- > >> mm/zsmalloc.c | 314 +++++++++++++++++++++++++++++++++++++----- > >> 3 files changed, 290 insertions(+), 33 deletions(-) > >> > >> -- > >> 1.8.3.1 > >> > >> -- > >> 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> > > > > -- > > Kind regards, > > Minchan Kim > > -- > 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> -- Kind regards, Minchan Kim -- 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>