On Thu, Jul 1, 2021 at 10:56 PM Minchan Kim <minchan@xxxxxxxxxx> wrote: > > On Wed, Jun 30, 2021 at 06:52:58PM -0700, Andrew Morton wrote: > > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > > Subject: mm: zram: amend SLAB_RECLAIM_ACCOUNT on zspage_cachep > > > > Zspage_cachep is found be merged with other kmem cache during test, which > > is not good for debug things (zs_pool->zspage_cachep present to be another > > kmem cache in memory dumpfile). It is also neccessary to do so as > > shrinker has been registered for zspage. > > > > Amending this flag can help kernel to calculate SLAB_RECLAIMBLE correctly. > > > > Link: https://lkml.kernel.org/r/1623137297-29685-1-git-send-email-huangzhaoyang@xxxxxxxxx > > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > > Cc: Minchan Kim <minchan@xxxxxxxxxx> > > Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx> > > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Sorry for the late. I don't think this is correct. > > It's true "struct zspage" can be freed by zsmalloc's compaction registerred > by slab shrinker so tempted to make it SLAB_RECLAIM_ACCOUNT. However, it's > quite limited to work only when objects in the zspage are heavily fragmented. > Once the compaction is done, zspage are never discardable until objects are > fragmented again. It means it could hurt other reclaimable slab page reclaiming > since the zspage slab object pins the page. IMHO, kmem cache's reclaiming is NOT affected by SLAB_RECLAIM_ACCOUNT . This flag just affects kmem cache merge[1], the slab page's migrate type[2] and the page's statistics. Actually, zspage's cache DO merged with others even without SLAB_RECLAIM_ACCOUNT currently, which maybe cause zspage's object will NEVER be discarded.(SLAB_MERGE_SAME introduce confusions as people believe the cache will merge with others when it set and vice versa) [1] struct kmem_cache *find_mergeable(size_t size, size_t align, unsigned long flags, const char *name, void (*ctor)(void *)) ... if ((flags & SLAB_MERGE_SAME) != (s->flags & SLAB_MERGE_SAME)) continue; [2] if (s->flags & SLAB_RECLAIM_ACCOUNT) s->allocflags |= __GFP_RECLAIMABLE; > > > --- > > > > mm/zsmalloc.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > --- a/mm/zsmalloc.c~mm-zram-amend-slab_reclaim_account-on-zspage_cachep > > +++ a/mm/zsmalloc.c > > @@ -328,7 +328,7 @@ static int create_cache(struct zs_pool * > > return 1; > > > > pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage), > > - 0, 0, NULL); > > + 0, SLAB_RECLAIM_ACCOUNT, NULL); > > if (!pool->zspage_cachep) { > > kmem_cache_destroy(pool->handle_cachep); > > pool->handle_cachep = NULL; > > _
