On Wed, 9 Jan 2013 18:10:02 +0400 Glauber Costa <glommer@xxxxxxxxxxxxx> wrote: > On 01/09/2013 01:44 AM, Andrew Morton wrote: > > On Fri, 4 Jan 2013 00:29:11 -0800 > > Anton Vorontsov <anton.vorontsov@xxxxxxxxxx> wrote: > > > >> This commit implements David Rientjes' idea of mempressure cgroup. > >> > >> The main characteristics are the same to what I've tried to add to vmevent > >> API; internally, it uses Mel Gorman's idea of scanned/reclaimed ratio for > >> pressure index calculation. But we don't expose the index to the userland. > >> Instead, there are three levels of the pressure: > >> > >> o low (just reclaiming, e.g. caches are draining); > >> o medium (allocation cost becomes high, e.g. swapping); > >> o oom (about to oom very soon). > >> > >> The rationale behind exposing levels and not the raw pressure index > >> described here: http://lkml.org/lkml/2012/11/16/675 > >> > >> For a task it is possible to be in both cpusets, memcg and mempressure > >> cgroups, so by rearranging the tasks it is possible to watch a specific > >> pressure (i.e. caused by cpuset and/or memcg). > >> > >> Note that while this adds the cgroups support, the code is well separated > >> and eventually we might add a lightweight, non-cgroups API, i.e. vmevent. > >> But this is another story. > >> > > > > I'd have thought that it's pretty important offer this feature to > > non-cgroups setups. Restricting it to cgroups-only seems a large > > limitation. > > > > Why is it so, Andrew? > > When we talk about "cgroups", we are not necessarily talking about the > whole beast, with all controllers enabled. Much less we are talking > about hierarchies being created, and tasks put on it. > > It's an interface only. And since all controllers will always have a > special "root" cgroup, this applies to the tasks in the system all the > same. In the end of the day, if we have something like > CONFIG_MEMPRESSURE that selects CONFIG_CGROUP, the user needs to do the > same thing to actually turn on the functionality: switch a config > option. It is not more expensive, and it doesn't bring in anything extra > as well. > > To actually use it, one needs to mount the filesystem, and write to a > file. Nothing else. > Oh, OK, well if the feature can be used in a system-wide fashion in this manner then I guess that is sufficient. For some reason I was thinking it was tied to memcg, doh. -- 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>