On Mon, Nov 09, 2015 at 02:32:53PM -0500, Tejun Heo wrote: > On Mon, Nov 09, 2015 at 10:27:47PM +0300, Vladimir Davydov wrote: > > Of course, we could rework slab merging so that kmem_cache_create > > returned a new dummy cache even if it was actually merged. Such a cache > > would point to the real cache, which would be used for allocations. This > > wouldn't limit slab merging, but this would add one more dereference to > > alloc path, which is even worse. > > Hmmm, this could be me not really understanding but why can't we let > all slabs to be merged regardless of SLAB_ACCOUNT flag for root memcg > and point to per-memcg slabs (may be merged among them but most likely Because we won't be able to distinguish kmem_cache_alloc calls that should be accounted from those that shouldn't. The problem is if two caches A = kmem_cache_create(...) and B = kmem_cache_create(...) happen to be merged, A and B will point to the same kmem_cache struct. As a result, there is no way to distinguish kmem_cache_alloc(A) which we want to account from kmem_cache_alloc(B) which we don't. > won't matter) for !root. We're indirecting once anyway, no? If kmem accounting is not used, we aren't indirecting. That's why I don't think we can use dummy kmem_cache struct for merged caches, where we could store __GFP_ACCOUNT flag. Thanks, Vladimir -- 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>