On Mon, Mar 15, 2010 at 11:36:12AM +0900, KAMEZAWA Hiroyuki wrote: > On Mon, 15 Mar 2010 00:26:37 +0100 > Andrea Righi <arighi@xxxxxxxxxxx> wrote: > > > 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. > > > Okay, thanks. This seems good result. Optimization for children can be done under > -mm tree, I think. (If no nack, this seems ready for test in -mm.) OK, I'll wait a bit to see if someone has other fixes or issues and post a new version soon including these small changes. Thanks, -Andrea -- 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>