On Mon, Sep 22, 2014 at 04:44:36PM +0200, Michal Hocko wrote: > On Fri 19-09-14 09:22:08, Johannes Weiner wrote: > > Memory is internally accounted in bytes, using spinlock-protected > > 64-bit counters, even though the smallest accounting delta is a page. > > The counter interface is also convoluted and does too many things. > > > > Introduce a new lockless word-sized page counter API, then change all > > memory accounting over to it and remove the old one. The translation > > from and to bytes then only happens when interfacing with userspace. > > Dunno why but I thought other controllers use res_counter as well. But > this doesn't seem to be the case so this is perfectly reasonable way > forward. You were fooled by its generic name! It really is a lot less generic than what it was designed for, and there are no new users in sight. > I have only glanced through the patch and it mostly seems good to me > (I have to look more closely on the atomicity of hierarchical operations). > > Nevertheless I think that the counter should live outside of memcg (it > is ugly and bad in general to make HUGETLB controller depend on MEMCG > just to have a counter). If you made kernel/page_counter.c and led both > containers select CONFIG_PAGE_COUNTER then you do not need a dependency > on MEMCG and I would find it cleaner in general. The reason I did it this way is because the hugetlb controller simply accounts and limits a certain type of memory and in the future I would like to make it a memcg extension, just like kmem and swap. Once that is done, page counters can become fully private, but until then I think it's a good idea to make them part of memcg to express this relationship and to ensure we are moving in the same direction. > > Aside from the locking costs, this gets rid of the icky unsigned long > > long types in the very heart of memcg, which is great for 32 bit and > > also makes the code a lot more readable. > > Definitely. Nice work! Thanks! -- 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>