2017-11-17 23:55 GMT+08:00 Roman Gushchin <guro@xxxxxx>: > On Thu, Nov 16, 2017 at 08:43:17PM -0800, Shakeel Butt wrote: >> On Thu, Nov 16, 2017 at 7:09 PM, Yafang Shao <laoar.shao@xxxxxxxxx> wrote: >> > Currently the default tmpfs size is totalram_pages / 2 if mount tmpfs >> > without "-o size=XXX". >> > When we mount tmpfs in a container(i.e. docker), it is also >> > totalram_pages / 2 regardless of the memory limit on this container. >> > That may easily cause OOM if tmpfs occupied too much memory when swap is >> > off. >> > So when we mount tmpfs in a memcg, the default size should be limited by >> > the memcg memory.limit. >> > >> >> The pages of the tmpfs files are charged to the memcg of allocators >> which can be in memcg different from the memcg in which the mount >> operation happened. So, tying the size of a tmpfs mount where it was >> mounted does not make much sense. > > Also, memory limit is adjustable, Yes. But that's irrelevant. > and using a particular limit value > at a moment of tmpfs mounting doesn't provide any warranties further. > I can not agree. The default size of tmpfs is totalram / 2, the reason we do this is to provide any warranties further IMHO. > Is there a reason why the userspace app which is mounting tmpfs can't > set the size based on memory.limit? That's because of misuse. The application should set size with "-o size=" when mount tmpfs, but not all applications do this. As we can't guarantee that all applications will do this, we should give them a proper default value. Thanks Yafang -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
