On Thu, Mar 11, 2010 at 09:39:13AM +0900, KAMEZAWA Hiroyuki wrote: > On Wed, 10 Mar 2010 00:00:31 +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 (v5 -> v6) > > ~~~~~~~~~~~~~~~~~~~~~~ > > * always disable/enable IRQs at lock/unlock_page_cgroup(): this allows to drop > > the previous complicated locking scheme in favor of a simpler locking, even > > if this obviously adds some overhead (see results below) > > * drop FUSE and NILFS2 dirty pages accounting for now (this depends on > > charging bounce pages per cgroup) > > > > Results > > ~~~~~~~ > > I ran some tests using a kernel build (2.6.33 x86_64_defconfig) on a > > Intel Core 2 @ 1.2GHz as testcase using different kernels: > > - mmotm "vanilla" > > - mmotm with cgroup-dirty-memory using the previous "complex" locking scheme > > (my previous patchset + the fixes reported by Kame-san and Daisuke-san) > > - mmotm with cgroup-dirty-memory using the simple locking scheme > > (lock_page_cgroup() with IRQs disabled) > > > > Following the results: > > <before> > > - mmotm "vanilla", root cgroup: 11m51.983s > > - mmotm "vanilla", child cgroup: 11m56.596s > > > > <after> > > - mmotm, "complex" locking scheme, root cgroup: 11m53.037s > > - mmotm, "complex" locking scheme, child cgroup: 11m57.896s > > > > - mmotm, lock_page_cgroup+irq_disabled, root cgroup: 12m5.499s > > - mmotm, lock_page_cgroup+irq_disabled, child cgroup: 12m9.920s > > > > With the "complex" locking solution, the overhead introduced by the > > cgroup dirty memory accounting is minimal (0.14%), compared with the overhead > > introduced by the lock_page_cgroup+irq_disabled solution (1.90%). > > > Hmm....isn't this bigger than expected ? Consider that I'm not running the kernel build on tmpfs, but on a fs defined on /dev/sda. So the additional overhead should be normal compared to the mmotm vanilla, where there's only FILE_MAPPED accounting. -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>