On 11/17/2016 02:32 AM, David Rientjes wrote: > Each zone's free_area tracks the number of free pages for all free lists. > This does not allow the number of free pages for a specific migratetype > to be determined without iterating its free list. > > An upcoming change will use this information to preclude doing async > memory compaction when the number of MIGRATE_UNMOVABLE pageblocks is > below a certain threshold. > > The total number of free pages is still tracked, however, to not make > zone_watermark_ok() more expensive. Reading /proc/pagetypeinfo, however, > is faster.
Yeah I've already seen a case with /proc/pagetypeinfo causing soft lockups due to high number of iterations... > This patch introduces no functional change and increases the amount of > per-zone metadata at worst by 48 bytes per memory zone (when CONFIG_CMA > and CONFIG_MEMORY_ISOLATION are enabled). Isn't it 48 bytes per zone and order? > Signed-off-by: David Rientjes <[email protected]> I'd be for this if there are no performance regressions. It affects hot paths and increases cache footprint. I think at least some allocator intensive microbenchmark should be used. Vlastimil
