On Thu, May 24, 2012 at 02:52:26PM -0700, David Rientjes wrote: > On Mon, 16 Apr 2012, Aneesh Kumar K.V wrote: > > > This patch implements a memcg extension that allows us to control HugeTLB > > allocations via memory controller. The extension allows to limit the > > HugeTLB usage per control group and enforces the controller limit during > > page fault. Since HugeTLB doesn't support page reclaim, enforcing the limit > > at page fault time implies that, the application will get SIGBUS signal if it > > tries to access HugeTLB pages beyond its limit. This requires the application > > to know beforehand how much HugeTLB pages it would require for its use. > > > > The charge/uncharge calls will be added to HugeTLB code in later patch. > > Support for memcg removal will be added in later patches. > > > > Again, I disagree with this approach because it's adding the functionality > to memcg when it's unnecessary; it would be a complete legitimate usecase > to want to limit the number of globally available hugepages to a set of > tasks without incurring the per-page tracking from memcg. > > This can be implemented as a seperate cgroup and as we move to a single > hierarchy, you lose no functionality if you mount both cgroups from what > is done here. > > It would be much cleaner in terms of > > - build: not requiring ifdefs and dependencies on CONFIG_HUGETLB_PAGE, > which is a prerequisite for this functionality and is not for > CONFIG_CGROUP_MEM_RES_CTLR, I am not sure we have large number of #ifdef as you have outlined above. Most of the hugetlb limit code is well isolated already. If we were to split it as a seperate controller, we will be duplicating code related cgroup deletion, migration support etc from memcg, because in case of memcg and hugetlb limit they depend on struct page. So I would expect we would be end up #ifdef around that code or duplicate them in the new controller if we were to do hugetlb limit as a seperate controller. Another reason for it to be part of memcg is, it is normal to look at hugetlb usage also as a memory usage. One of the feedback I got for the earlier post is to see if i can enhace the current code to make sure memory.usage_in_bytes can also account for hugetlb usage. People would also like to look at memory.limit_in_bytes to limit total usage. (inclusive of hugetlb). > > - code: seperating hugetlb bits out from memcg bits to avoid growing > mm/memcontrol.c beyond its current 5650 lines, and > I can definitely look at spliting mm/memcontrol.c > - performance: not incurring any overhead of enabling memcg for per- > page tracking that is unnecessary if users only want to limit hugetlb > pages. > -aneesh -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>