On 06/18/2012 04:10 PM, Kamezawa Hiroyuki wrote: > (2012/06/18 19:27), Glauber Costa wrote: >> Hello All, >> >> This is my new take for the memcg kmem accounting. This should merge >> all of the previous comments from you guys, specially concerning the big churn >> inside the allocators themselves. >> >> My focus in this new round was to keep the changes in the cache internals to >> a minimum. To do that, I relied upon two main pillars: >> >> * Cristoph's unification series, that allowed me to put must of the changes >> in a common file. Even then, the changes are not too many, since the overal >> level of invasiveness was decreased. >> * Accounting is done directly from the page allocator. This means some pages >> can fail to be accounted, but that can only happen when the task calling >> kmem_cache_alloc or kmalloc is not the same task allocating a new page. >> This never happens in steady state operation if the tasks are kept in the >> same memcg. Naturally, if the page ends up being accounted to a memcg that >> is not limited (such as root memcg), that particular page will simply not >> be accounted. >> >> The dispatcher code stays (mem_cgroup_get_kmem_cache), being the mechanism who >> guarantees that, during steady state operation, all objects allocated in a page >> will belong to the same memcg. I consider this a good compromise point between >> strict and loose accounting here. >> > > 2 questions. > > - Do you have performance numbers ? Not extensive. I've run some microbenchmarks trying to determine the effect of my code on kmem_cache_alloc, and found it to be in the order of 2 to 3 %. I would expect that to vanish in a workload benchmark. > > - Do you think user-memory memcg should be switched to page-allocator level accounting ? > (it will require some study for modifying current bached-freeing and per-cpu-stock > logics...) I don't see a reason for that. My main goal by doing that was to reduce the churn in the cache internal structures, but specially because there is at least two of them, obeying a stable interface. The way I understand it, memcg for user pages is already pretty well integrated to the page allocator, so the benefit of it is questionable. -- 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>