(2012/03/23 17:59), bill4carson wrote: > > > On 2012年03月23日 16:19, KAMEZAWA Hiroyuki wrote: >> (2012/03/23 17:04), bill4carson wrote: >> >>> Hi, all >>> >>> I'm playing with memory cgroup, I'm a bit confused why >>> memory.usage in bytes is steadily increasing at 4K page pace >>> after every mmap/dirty/unmap sequence. >>> >>> On linux-3.6.34.10/linux-3.3.0-rc5 >>> A simple test case does following: >>> >>> a) mmap 128k memory in private anonymous way >>> b) dirty all 128k to demand physical page >>> c) print memory.usage_in_bytes<-- increased at 4K after every loop >>> d) unmap previous 128 memory >>> e) goto a) to repeat >> >> In Documentation/cgroup/memory.txt >> == >> 5.5 usage_in_bytes >> >> For efficiency, as other kernel components, memory cgroup uses some optimization >> to avoid unnecessary cacheline false sharing. usage_in_bytes is affected by the >> method and doesn't show 'exact' value of memory(and swap) usage, it's an fuzz >> value for efficient access. (Of course, when necessary, it's synchronized.) >> If you want to know more exact memory usage, you should use RSS+CACHE(+SWAP) >> value in memory.stat(see 5.2). >> == >> >> In current implementation, memcg tries to charge resource in size of 32 pages. >> So, if you get 32 pages and free 32pages, usage_in_bytes may not change. >> This is affected by caches in other cpus and other flushing operations caused >> by some workload in other cgroups. memcg's usage_in_bytes is not precise in >> 128k degree. >> > Yes, I tried to mmap/dirty/unmap in 32 times, when the usage_in_bytes > reached 128k, it rolls back to 4k again. So it doesn't hurt any more. rolls back before unmap() ? > > I haven't found the code regarding to this behavior. Could you post your test program ? Thanks, -Kame -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>