* Andrea Righi <arighi@xxxxxxxxxxx> [2010-03-15 00:26:37]: > Control the maximum amount of dirty pages a cgroup can have at any given time. > > Per cgroup dirty limit is like fixing the max amount of dirty (hard to reclaim) > page cache used by any cgroup. So, in case of multiple cgroup writers, they > will not be able to consume more than their designated share of dirty pages and > will be forced to perform write-out if they cross that limit. > > The overall design is the following: > > - account dirty pages per cgroup > - limit the number of dirty pages via memory.dirty_ratio / memory.dirty_bytes > and memory.dirty_background_ratio / memory.dirty_background_bytes in > cgroupfs > - start to write-out (background or actively) when the cgroup limits are > exceeded > > This feature is supposed to be strictly connected to any underlying IO > controller implementation, so we can stop increasing dirty pages in VM layer > and enforce a write-out before any cgroup will consume the global amount of > dirty pages defined by the /proc/sys/vm/dirty_ratio|dirty_bytes and > /proc/sys/vm/dirty_background_ratio|dirty_background_bytes limits. > > Changelog (v6 -> v7) > ~~~~~~~~~~~~~~~~~~~~~~ > * introduce trylock_page_cgroup() to guarantee that lock_page_cgroup() > is never called under tree_lock (no strict accounting, but better overall > performance) > * do not account file cache statistics for the root cgroup (zero > overhead for the root cgroup) > * fix: evaluate cgroup free pages as at the minimum free pages of all > its parents > > Results > ~~~~~~~ > The testcase is a kernel build (2.6.33 x86_64_defconfig) on a Intel Core 2 @ > 1.2GHz: > > <before> > - root cgroup: 11m51.983s > - child cgroup: 11m56.596s > > <after> > - root cgroup: 11m51.742s > - child cgroup: 12m5.016s > > In the previous version of this patchset, using the "complex" locking scheme > with the _locked and _unlocked version of mem_cgroup_update_page_stat(), the > child cgroup required 11m57.896s and 12m9.920s with lock_page_cgroup()+irq_disabled. > > With this version there's no overhead for the root cgroup (the small difference > is in error range). I expected to see less overhead for the child cgroup, I'll > do more testing and try to figure better what's happening. I like that the root overhead is going away. > > In the while, it would be great if someone could perform some tests on a larger > system... unfortunately at the moment I don't have a big system available for > this kind of tests... > I'll test this, I have a small machine to test on at the moment, I'll revert back with data. -- Three Cheers, Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>