在 2012-9-5，下午4:11，Minchan Kim <[email protected]> 写道：
> This patch introudes MIGRATE_DISCARD mode in migration. > It drops *clean cache pages* instead of migration so that > migration latency could be reduced by avoiding (memcpy + page remapping). > It's useful for CMA because latency of migration is very important rather > than eviction of background processes's workingset. In addition, it needs > less free pages for migration targets so it could avoid memory reclaiming > to get free pages, which is another factor increase latency. > > Cc: Marek Szyprowski <[email protected]> > Cc: Michal Nazarewicz <[email protected]> > Cc: Rik van Riel <[email protected]> > Cc: Mel Gorman <[email protected]> > Signed-off-by: Minchan Kim <[email protected]> > --- > include/linux/migrate_mode.h | 7 +++++++ > mm/migrate.c | 41 ++++++++++++++++++++++++++++++++++++++--- > mm/page_alloc.c | 2 +- > 3 files changed, 46 insertions(+), 4 deletions(-) > > diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h > index 8848cad..4eb1646 100644 > --- a/include/linux/migrate_mode.h > +++ b/include/linux/migrate_mode.h > @@ -14,6 +14,13 @@ > */ > #define MIGRATE_SYNC ((__force migrate_mode_t)0x4) > > +/* > + * MIGRTATE_DISCARD will discard clean cache page instead of migration. > + * MIGRATE_ASYNC, MIGRATE_SYNC_LIGHT, MIGRATE_SYNC shouldn't be used > + * together with OR flag in current implementation. > + */ > +#define MIGRATE_DISCARD ((__force migrate_mode_t)0x8) > + > typedef unsigned __bitwise__ migrate_mode_t; > > #endif /* MIGRATE_MODE_H_INCLUDED */ > diff --git a/mm/migrate.c b/mm/migrate.c > index 28d464b..2de7709 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -678,6 +678,19 @@ static int move_to_new_page(struct page *newpage, struct > page *page, > return rc; > } > > +static int discard_page(struct page *page) > +{ > + int ret = -EAGAIN; > + > + struct address_space *mapping = page_mapping(page); > + if (page_has_private(page)) > + if (!try_to_release_page(page, GFP_KERNEL)) > + return ret; > + if (remove_mapping(mapping, page)) > + ret = 0; > + return ret; > +} > + > static int __unmap_and_move(struct page *page, struct page *newpage, > int force, bool offlining, migrate_mode_t mode) > { > @@ -685,6 +698,9 @@ static int __unmap_and_move(struct page *page, struct > page *newpage, > int remap_swapcache = 1; > struct mem_cgroup *mem; > struct anon_vma *anon_vma = NULL; > + enum ttu_flags ttu_flags; > + bool discard_mode = false; > + bool file = false; > > if (!trylock_page(page)) { > if (!force || (mode & MIGRATE_ASYNC)) > @@ -799,12 +815,31 @@ static int __unmap_and_move(struct page *page, struct > page *newpage, > goto skip_unmap; > } > > + file = page_is_file_cache(page); > + ttu_flags = TTU_IGNORE_ACCESS; > +retry: > + if (!(mode & MIGRATE_DISCARD) || !file || PageDirty(page)) > + ttu_flags |= (TTU_MIGRATION | TTU_IGNORE_MLOCK); > + else > + discard_mode = true; > + > /* Establish migration ptes or remove ptes */ > - try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); > + rc = try_to_unmap(page, ttu_flags); > > skip_unmap: > - if (!page_mapped(page)) > - rc = move_to_new_page(newpage, page, remap_swapcache, mode); > + if (rc == SWAP_SUCCESS) { > + if (!discard_mode) { > + rc = move_to_new_page(newpage, page, > + remap_swapcache, mode); > + } else { > + rc = discard_page(page); > + goto uncharge; > + } > + } else if (rc == SWAP_MLOCK && discard_mode) { > + mode &= ~MIGRATE_DISCARD; > + discard_mode = false; > + goto retry; > + } > > if (rc && remap_swapcache) > remove_migration_ptes(page, page); > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ba3100a..e14b960 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5670,7 +5670,7 @@ static int __alloc_contig_migrate_range(unsigned long > start, unsigned long end) > > ret = migrate_pages(&cc.migratepages, > __alloc_contig_migrate_alloc, > - 0, false, MIGRATE_SYNC); > + 0, false, MIGRATE_SYNC|MIGRATE_DISCARD); > } > > putback_lru_pages(&cc.migratepages); > -- > 1.7.9.5 > > -- > 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/ -- 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/
