On Mon, 30 Mar 2015, Andrew Morton wrote: > On Mon, 30 Mar 2015 14:31:14 -0400 Eric B Munson <emunson@xxxxxxxxxx> wrote: > > > The memory compaction code uses the migration code to do most of the > > work in compaction. However, the compaction code interacts with the > > unevictable LRU differently than migration code and this difference > > should be noted in the documentation. > > > > --- a/Documentation/vm/unevictable-lru.txt > > +++ b/Documentation/vm/unevictable-lru.txt > > @@ -450,6 +451,16 @@ list because of a race between munlock and migration, page migration uses the > > putback_lru_page() function to add migrated pages back to the LRU. > > > > > > +COMPACTING MLOCKED PAGES > > +------------------------ > > + > > +The unevictable LRU can be scanned for compactable regions and the default > > +behavior is to do so. There is a sysctl to control this behavior (see > > +Documentation/sysctl/vm.txt). Once scanning of the unevictable LRU is > > +enabled, the work of compaction is mostly handled by the page migration code > > +and the same work flow as described in MIGRATING MLOCKED PAGES will apply. > > + > > Thanks. Let's tell people what this sysctl is called? > > > s@There is a sysctl to control@/proc/sys/vm/compact_unevictable_allowed controls@: > > --- a/Documentation/vm/unevictable-lru.txt~document-interaction-between-compaction-and-the-unevictable-lru-fix > +++ a/Documentation/vm/unevictable-lru.txt > @@ -455,10 +455,11 @@ COMPACTING MLOCKED PAGES > ------------------------ > > The unevictable LRU can be scanned for compactable regions and the default > -behavior is to do so. There is a sysctl to control this behavior (see > -Documentation/sysctl/vm.txt). Once scanning of the unevictable LRU is > -enabled, the work of compaction is mostly handled by the page migration code > -and the same work flow as described in MIGRATING MLOCKED PAGES will apply. > +behavior is to do so. /proc/sys/vm/compact_unevictable_allowed controls > +this behavior (see Documentation/sysctl/vm.txt). Once scanning of the > +unevictable LRU is enabled, the work of compaction is mostly handled by > +the page migration code and the same work flow as described in MIGRATING > +MLOCKED PAGES will apply. > > > mmap(MAP_LOCKED) SYSTEM CALL HANDLING > _ > That looks good, thanks. Eric
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