On Thu, Nov 06, 2014 at 09:01:52AM -0600, Christoph Lameter wrote: > On Thu, 6 Nov 2014, Vladimir Davydov wrote: > > > I call memcg_kmem_recharge_slab only on alloc path. Free path isn't > > touched. The overhead added is one function call. The function only > > reads and compares two pointers under RCU most of time. This is > > comparable to the overhead introduced by memcg_kmem_get_cache, which is > > called in slab_alloc/slab_alloc_node earlier. > > Right maybe remove those too? Things seem to be accumulating in the hot > path which is bad. There is a slow path where these things can be added > and also a page based even slower path for statistics keeping. > > The approach in SLUB is to do accounting on a slab page basis. Also memory > policies are applied at page granularity not object granularity. > > > Anyways, if you think this is unacceptable, I don't mind dropping the > > whole patch set and thinking more on how to fix this per-memcg caches > > trickery. What do you think? > > Maybe its possible to just use slab page accounting instead of object > accounting? Reduces overhead significantly. There may be some fuzz here > with occasional object accounted in the wrong way (which is similar to how > memory policies and other methods work) but it has been done before and > works ok. Actually, it's not about mis-accounting. The problem is a newly allocated object can pin a charge of a dead cgroup that used the cache before. May be, it wouldn't be a problem though. Anyways, I think I need more time to brood over the whole approach, so I've asked Andrew to drop the patch set. Thank you for the feedback! -- 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>