Johannes Weiner wrote:
On Wed, Feb 15, 2012 at 08:24:42PM +0400, Konstantin Khlebnikov wrote:
This patch adds mem_cgroup->inactive_ratio calculated from hierarchical memory limit.
It updated at each limit change before shrinking cgroup to this new limit.
Ratios for all child cgroups are updated too, because parent limit can affect them.
Update precedure can be greatly optimized if its performance becomes the problem.
Inactive ratio for unlimited or huge limit does not matter, because we'll never hit it.
At global reclaim always use global ratio from zone->inactive_ratio.
At mem-cgroup reclaim use inactive_ratio from target memory cgroup,
this is cgroup which hit its limit and cause this reclaimer invocation.
Thus, global memory reclaimer will try to keep ratio for all lru lists in zone
above one mark, this guarantee that total ratio in this zone will be above too.
Meanwhile mem-cgroup will do the same thing for its lru lists in all zones, and
for all lru lists in all sub-cgroups in hierarchy.
Also this patch removes some redundant code.
Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
I don't think we should take the zone ratio when we then proceed to
scan a bunch of LRU lists that could individually be much smaller than
the zone. Especially since the ratio function is not a linear one.
Otherwise the target ratios can be way too big for small lists, see
the comment above mm/page_alloc.c::calculate_zone_inactive_ratio().
Consequently, I also disagree on using sc->target_mem_cgroup.
This whole mechanism is about balancing one specific pair of inactive
vs. an active list according their size. We shouldn't derive policy
from numbers that are not correlated to this size.
Ok, maybe then we can move this inactive_ratio calculation right into
inactive_anon_is_low(). Then we can kill precalculated zone->inactive_ratio
and calculate it every time, even in non-memcg case, because zone-size also
not always correlate with anon lru size.
Looks like int_sqrt() is fast enough for this.
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