On Fri, Feb 3, 2012 at 1:40 AM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
> If moving dirty pages out of the memcg to the 20% global dirty pages
> pool on page reclaim, the above OOM can be avoided. It does change the
> meaning of memory.limit_in_bytes in that the memcg tasks can now
> actually consume more pages (up to the shared global 20% dirty limit).
This seems like an easy change, but unfortunately the global 20% pool
has some shortcomings for my needs:
1. the global 20% pool is not moderated. One cgroup can dominate it
and deny service to other cgroups.
2. the global 20% pool is free, unaccounted memory. Ideally cgroups only
use the amount of memory specified in their memory.limit_in_bytes. The
goal is to sell portions of a system. Global resource like the 20% are an
undesirable system-wide tax that's shared by jobs that may not even
perform buffered writes.
3. Setting aside 20% extra memory for system wide dirty buffers is a lot of
memory. This becomes a larger issue when the global dirty_ratio is
higher than 20%.
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