"Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> writes: > 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. >> Since Andrew didn't sent the patchset to Linus because of this discussion, I looked at reworking the patchset as a seperate controller. The patchset I sent here http://thread.gmane.org/gmane.linux.kernel.mm/79230 have seen minimal testing. I also folded the fixup patches Andrew had in -mm to original patchset. Let me know if the changes looks good. -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>