[patch v4 4/6] mm, compaction: embed migration mode in compact_control

David Rientjes
2014-05-07T10:36:52Z

We're going to want to manipulate the migration mode for compaction in the page
allocator, and currently compact_control's sync field is only a bool.

Currently, we only do MIGRATE_ASYNC or MIGRATE_SYNC_LIGHT compaction depending
on the value of this bool. Convert the bool to enum migrate_mode and pass the
migration mode in directly. Later, we'll want to avoid MIGRATE_SYNC_LIGHT for
thp allocations in the pagefault patch to avoid unnecessary latency.

This also alters compaction triggered from sysfs, either for the entire system
or for a node, to force MIGRATE_SYNC.

Suggested-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: David Rientjes <rientjes@google.com>
---
v4 of this patch only: converted name of formal from "sync" to "mode" for
try_to_compact_pages() per Vlastimil

include/linux/compaction.h | 4 ++--
mm/compaction.c | 38 ++++++++++++++++++++------------------
mm/internal.h | 2 +-
mm/page_alloc.c | 37 ++++++++++++++++---------------------
4 files changed, 39 insertions(+), 42 deletions(-)

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -22,7 +22,7 @@ extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
extern int fragmentation_index(struct zone *zone, unsigned int order);
extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *mask,
- bool sync, bool *contended);
+ enum migrate_mode mode, bool *contended);
extern void compact_pgdat(pg_data_t *pgdat, int order);
extern void reset_isolation_suitable(pg_data_t *pgdat);
extern unsigned long compaction_suitable(struct zone *zone, int order);
@@ -91,7 +91,7 @@ static inline bool compaction_restarting(struct zone *zone, int order)
#else
static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *nodemask,
- bool sync, bool *contended)
+ enum migrate_mode mode, bool *contended)
{
return COMPACT_CONTINUE;
}
diff --git a/mm/compaction.c b/mm/compaction.c
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -161,7 +161,8 @@ static void update_pageblock_skip(struct compact_control *cc,
return;
if (pfn > zone->compact_cached_migrate_pfn[0])
zone->compact_cached_migrate_pfn[0] = pfn;
- if (cc->sync && pfn > zone->compact_cached_migrate_pfn[1])
+ if (cc->mode != MIGRATE_ASYNC &&
+ pfn > zone->compact_cached_migrate_pfn[1])
zone->compact_cached_migrate_pfn[1] = pfn;
} else {
if (cc->finished_update_free)
@@ -208,7 +209,7 @@ static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags,
}

/* async aborts if taking too long or contended */
- if (!cc->sync) {
+ if (cc->mode == MIGRATE_ASYNC) {
cc->contended = true;
return false;
}
@@ -479,7 +480,8 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
bool locked = false;
struct page *page = NULL, *valid_page = NULL;
bool set_unsuitable = true;
- const isolate_mode_t mode = (!cc->sync ? ISOLATE_ASYNC_MIGRATE : 0) |
+ const isolate_mode_t mode = (cc->mode == MIGRATE_ASYNC ?
+ ISOLATE_ASYNC_MIGRATE : 0) |
(unevictable ? ISOLATE_UNEVICTABLE : 0);

/*
@@ -489,7 +491,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
*/
while (unlikely(too_many_isolated(zone))) {
/* async migration should just abort */
- if (!cc->sync)
+ if (cc->mode == MIGRATE_ASYNC)
return 0;

congestion_wait(BLK_RW_ASYNC, HZ/10);
@@ -554,7 +556,8 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
* the minimum amount of work satisfies the allocation
*/
mt = get_pageblock_migratetype(page);
- if (!cc->sync && !migrate_async_suitable(mt)) {
+ if (cc->mode == MIGRATE_ASYNC &&
+ !migrate_async_suitable(mt)) {
set_unsuitable = false;
goto next_pageblock;
}
@@ -990,6 +993,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
int ret;
unsigned long start_pfn = zone->zone_start_pfn;
unsigned long end_pfn = zone_end_pfn(zone);
+ const bool sync = cc->mode != MIGRATE_ASYNC;

ret = compaction_suitable(zone, cc->order);
switch (ret) {
@@ -1015,7 +1019,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
* information on where the scanners should start but check that it
* is initialised by ensuring the values are within zone boundaries.
*/
- cc->migrate_pfn = zone->compact_cached_migrate_pfn[cc->sync];
+ cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
cc->free_pfn = zone->compact_cached_free_pfn;
if (cc->free_pfn < start_pfn || cc->free_pfn > end_pfn) {
cc->free_pfn = end_pfn & ~(pageblock_nr_pages-1);
@@ -1049,8 +1053,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)

nr_migrate = cc->nr_migratepages;
err = migrate_pages(&cc->migratepages, compaction_alloc,
- compaction_free, (unsigned long)cc,
- cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC,
+ compaction_free, (unsigned long)cc, cc->mode,
MR_COMPACTION);
update_nr_listpages(cc);
nr_remaining = cc->nr_migratepages;
@@ -1083,9 +1086,8 @@ out:
return ret;
}

-static unsigned long compact_zone_order(struct zone *zone,
- int order, gfp_t gfp_mask,
- bool sync, bool *contended)
+static unsigned long compact_zone_order(struct zone *zone, int order,
+ gfp_t gfp_mask, enum migrate_mode mode, bool *contended)
{
unsigned long ret;
struct compact_control cc = {
@@ -1094,7 +1096,7 @@ static unsigned long compact_zone_order(struct zone *zone,
.order = order,
.migratetype = allocflags_to_migratetype(gfp_mask),
.zone = zone,
- .sync = sync,
+ .mode = mode,
};
INIT_LIST_HEAD(&cc.freepages);
INIT_LIST_HEAD(&cc.migratepages);
@@ -1116,7 +1118,7 @@ int sysctl_extfrag_threshold = 500;
* @order: The order of the current allocation
* @gfp_mask: The GFP mask of the current allocation
* @nodemask: The allowed nodes to allocate from
- * @sync: Whether migration is synchronous or not
+ * @mode: The migration mode for async, sync light, or sync migration
* @contended: Return value that is true if compaction was aborted due to lock contention
* @page: Optionally capture a free page of the requested order during compaction
*
@@ -1124,7 +1126,7 @@ int sysctl_extfrag_threshold = 500;
*/
unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *nodemask,
- bool sync, bool *contended)
+ enum migrate_mode mode, bool *contended)
{
enum zone_type high_zoneidx = gfp_zone(gfp_mask);
int may_enter_fs = gfp_mask & __GFP_FS;
@@ -1149,7 +1151,7 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
nodemask) {
int status;

- status = compact_zone_order(zone, order, gfp_mask, sync,
+ status = compact_zone_order(zone, order, gfp_mask, mode,
contended);
rc = max(status, rc);

@@ -1189,7 +1191,7 @@ static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
low_wmark_pages(zone), 0, 0))
compaction_defer_reset(zone, cc->order, false);
/* Currently async compaction is never deferred. */
- else if (cc->sync)
+ else if (cc->mode != MIGRATE_ASYNC)
defer_compaction(zone, cc->order);
}

@@ -1202,7 +1204,7 @@ void compact_pgdat(pg_data_t *pgdat, int order)
{
struct compact_control cc = {
.order = order,
- .sync = false,
+ .mode = MIGRATE_ASYNC,
};

if (!order)
@@ -1215,7 +1217,7 @@ static void compact_node(int nid)
{
struct compact_control cc = {
.order = -1,
- .sync = true,
+ .mode = MIGRATE_SYNC,
.ignore_skip_hint = true,
};

diff --git a/mm/internal.h b/mm/internal.h
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -134,7 +134,7 @@ struct compact_control {
unsigned long nr_migratepages; /* Number of pages to migrate */
unsigned long free_pfn; /* isolate_freepages search base */
unsigned long migrate_pfn; /* isolate_migratepages search base */
- bool sync; /* Synchronous migration */
+ enum migrate_mode mode; /* Async or sync migration mode */
bool ignore_skip_hint; /* Scan blocks even if marked skip */
bool finished_update_free; /* True when the zone cached pfns are
* no longer being updated
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2226,7 +2226,7 @@ static struct page *
__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, enum zone_type high_zoneidx,
nodemask_t *nodemask, int alloc_flags, struct zone *preferred_zone,
- int migratetype, bool sync_migration,
+ int migratetype, enum migrate_mode mode,
bool *contended_compaction, bool *deferred_compaction,
unsigned long *did_some_progress)
{
@@ -2240,7 +2240,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,

current->flags |= PF_MEMALLOC;
*did_some_progress = try_to_compact_pages(zonelist, order, gfp_mask,
- nodemask, sync_migration,
+ nodemask, mode,
contended_compaction);
current->flags &= ~PF_MEMALLOC;

@@ -2273,7 +2273,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
* As async compaction considers a subset of pageblocks, only
* defer if the failure was a sync compaction failure.
*/
- if (sync_migration)
+ if (mode != MIGRATE_ASYNC)
defer_compaction(preferred_zone, order);

cond_resched();
@@ -2286,9 +2286,8 @@ static inline struct page *
__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, enum zone_type high_zoneidx,
nodemask_t *nodemask, int alloc_flags, struct zone *preferred_zone,
- int migratetype, bool sync_migration,
- bool *contended_compaction, bool *deferred_compaction,
- unsigned long *did_some_progress)
+ int migratetype, enum migrate_mode mode, bool *contended_compaction,
+ bool *deferred_compaction, unsigned long *did_some_progress)
{
return NULL;
}
@@ -2483,7 +2482,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
int alloc_flags;
unsigned long pages_reclaimed = 0;
unsigned long did_some_progress;
- bool sync_migration = false;
+ enum migrate_mode migration_mode = MIGRATE_ASYNC;
bool deferred_compaction = false;
bool contended_compaction = false;

@@ -2577,17 +2576,15 @@ rebalance:
* Try direct compaction. The first pass is asynchronous. Subsequent
* attempts after direct reclaim are synchronous
*/
- page = __alloc_pages_direct_compact(gfp_mask, order,
- zonelist, high_zoneidx,
- nodemask,
- alloc_flags, preferred_zone,
- migratetype, sync_migration,
- &contended_compaction,
+ page = __alloc_pages_direct_compact(gfp_mask, order, zonelist,
+ high_zoneidx, nodemask, alloc_flags,
+ preferred_zone, migratetype,
+ migration_mode, &contended_compaction,
&deferred_compaction,
&did_some_progress);
if (page)
goto got_pg;
- sync_migration = true;
+ migration_mode = MIGRATE_SYNC_LIGHT;

/*
* If compaction is deferred for high-order allocations, it is because
@@ -2662,12 +2659,10 @@ rebalance:
* direct reclaim and reclaim/compaction depends on compaction
* being called after reclaim so call directly if necessary
*/
- page = __alloc_pages_direct_compact(gfp_mask, order,
- zonelist, high_zoneidx,
- nodemask,
- alloc_flags, preferred_zone,
- migratetype, sync_migration,
- &contended_compaction,
+ page = __alloc_pages_direct_compact(gfp_mask, order, zonelist,
+ high_zoneidx, nodemask, alloc_flags,
+ preferred_zone, migratetype,
+ migration_mode, &contended_compaction,
&deferred_compaction,
&did_some_progress);
if (page)
@@ -6254,7 +6249,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
.nr_migratepages = 0,
.order = -1,
.zone = page_zone(pfn_to_page(start)),
- .sync = true,
+ .sync = MIGRATE_SYNC_LIGHT,
.ignore_skip_hint = true,
};
INIT_LIST_HEAD(&cc.migratepages);