On Nov 29, 2007 6:11 PM, Nick Piggin <[EMAIL PROTECTED]> wrote: > And also some > results or even anecdotes of where this is going to be used would be > interesting...
We want to be able to run multiple isolated jobs on the same machine. So being able to limit how much memory each job can consume, in terms of anonymous memory and page cache, are useful. I've not had much time to look at the patches in great detail, but they seem to provide a sensible way to assign and enforce static limits on a bunch of jobs. Some of our requirements are a bit beyond this, though: In our experience, users are not good at figuring out how much memory they really need. In general they tend to massively over-estimate their requirements. So we want some way to determine how much of its allocated memory a job is actively using, and how much could be thrown away or swapped out without bothering the job too much. Of course, the definition of "actve use" is tricky - one possibility that we're looking at is "has been accessed within the last N seconds", where N can be configured appropriately for different jobs depending on the job's latency requirements. Active use should also be reported for pages that can't be easily freed quickly, e.g. mlocked or dirty pages, or anon pages on a swapless system. Inactive pages should be easily freeable, and be the first ones to go in the event of memory pressure. (From a scheduling point of view we can treat them as free memory, and schedule more jobs on the machine) The existing active/inactive distinction doesn't really capture this, since it's relative rather than absolute. We want to be able to overcommit a machine, so the sums of the cgroup memory limits can add up to more than the total machine memory. So we need control over what happens when there's global memory pressure, and a way to ensure that the low-latency jobs don't get bogged down in reclaim (or OOM) due to the activity of batch jobs. Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
