* KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-06-28 11:03:27]: > On Fri, 25 Jun 2010 13:43:45 -0700 > Greg Thelen <gthelen@xxxxxxxxxx> wrote: > > > For the upcoming Linux VM summit, I am interesting in discussing the > > following proposal. > > > > Problem: When tasks from multiple cgroups share files the charging can be > > non-deterministic. This requires that all such cgroups have unnecessarily high > > limits. It would be nice if the charging was deterministic, using the file's > > path to determine which cgroup to charge. This would benefit charging of > > commonly used files (eg: libc) as well as large databases shared by only a few > > tasks. > > > > Example: assume two tasks (T1 and T2), each in a separate cgroup. Each task > > wants to access a large (1GB) database file. To catch memory leaks a tight > > memory limit on each task's cgroup is set. However, the large database file > > presents a problem. If the file has not been cached, then the first task to > > access the file is charged, thereby requiring that task's cgroup to have a limit > > large enough to include the database file. If the order of access is unknown > > (due to process restart, etc), then all cgroups accessing the file need to have > > a limit large enough to include the database. This is wasteful because the > > database won't be charged to both T1 and T2. It would be useful to introduce > > determinism by declaring that a particular cgroup is charged for a particular > > set of files. > > > > /dev/cgroup/cg1/cg11 # T1: want memory.limit = 30MB > > /dev/cgroup/cg1/cg12 # T2: want memory.limit = 100MB > > /dev/cgroup/cg1 # want memory.limit = 1GB + 30MB + 100MB > > > > I have implemented a prototype that allows a file system hierarchy be charge a > > particular cgroup using a new bind mount option: > > + mount -t cgroup none /cgroup -o memory > > + mount --bind /tmp/db /tmp/db -o cgroup=/dev/cgroup/cg1 > > > > Any accesses to files within /tmp/db are charged to /dev/cgroup/cg1. Access to > > other files behave normally - they charge the cgroup of the current task. > > > > Interesting, but I want to use madvice() etc..for this kind of jobs, rather than > deep hooks into the kernel. > > madvise(addr, size, MEMORY_RECHAEGE_THIS_PAGES_TO_ME); > > Then, you can write a command as: > > file_recharge [path name] [cgroup] > - this commands move a file cache to specified cgroup. > > A daemon program which uses this command + inotify will give us much > flexible controls on file cache on memcg. Do you have some requirements > that this move-charge shouldn't be done in lazy manner ? > > Status: > We have codes for move-charge, inotify but have no code for new madvise. I have not see the approach yet, but ideally one would want to avoid changing the application, otherwise we are going to get very tightly bound in the API issues. I want to understand why do we need bind mounts? I think this needs more discussion. -- 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>