On Thu, Mar 11, 2010 at 01:07:53PM -0500, Vivek Goyal wrote: > On Wed, Mar 10, 2010 at 12:00:31AM +0100, Andrea Righi 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. > > > > Hi Andrea, > > I am doing a simple dd test of writting a 4G file. This machine has got > 64G of memory and I have created one cgroup with 100M as limit_in_bytes. > > I run following dd program both in root cgroup as well as test1/ > cgroup(100M limit) one after the other. > > In root cgroup > ============== > dd if=/dev/zero of=/root/zerofile bs=4K count=1000000 > 1000000+0 records in > 1000000+0 records out > 4096000000 bytes (4.1 GB) copied, 59.5571 s, 68.8 MB/s > > In test1/ cgroup > =============== > dd if=/dev/zero of=/root/zerofile bs=4K count=1000000 > 1000000+0 records in > 1000000+0 records out > 4096000000 bytes (4.1 GB) copied, 20.6683 s, 198 MB/s > > It is strange that we are throttling process in root group much more than > process in test1/ cgroup? mmmh.. strange, on my side I get something as expected: <root cgroup> $ dd if=/dev/zero of=test bs=1M count=500 500+0 records in 500+0 records out 524288000 bytes (524 MB) copied, 6.28377 s, 83.4 MB/s <child cgroup with 100M memory.limit_in_bytes> $ dd if=/dev/zero of=test bs=1M count=500 500+0 records in 500+0 records out 524288000 bytes (524 MB) copied, 11.8884 s, 44.1 MB/s Did you change the global /proc/sys/vm/dirty_* or memcg dirty parameters? -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>