return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
}
+/*
+ * Check that the whole (or subset of) a pageblock given by the interval of
+ * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
+ * with the migration of free compaction scanner. The scanners then need to
+ * use only pfn_valid_within() check for arches that allow holes within
+ * pageblocks.
+ *
+ * Return struct page pointer of start_pfn, or NULL if checks were not passed.
+ *
+ * It's possible on some configurations to have a setup like node0 node1 node0
+ * i.e. it's possible that all pages within a zones range of pages do not
+ * belong to a single zone. We assume that a border between node0 and node1
+ * can occur within a single pageblock, but not a node0 node1 node0
+ * interleaving within a single pageblock. It is therefore sufficient to check
+ * the first and last page of a pageblock and avoid checking each individual
+ * page in a pageblock.
+ */
+static struct page *pageblock_pfn_to_page(unsigned long start_pfn,
+ unsigned long end_pfn, struct zone *zone)
+{
+ struct page *start_page;
+ struct page *end_page;
+
+ /* end_pfn is one past the range we are checking */
+ end_pfn--;
+
+ if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn))
+ return NULL;
+
+ start_page = pfn_to_page(start_pfn);
+
+ if (page_zone(start_page) != zone)
+ return NULL;
+
+ end_page = pfn_to_page(end_pfn);
+
+ /* This gives a shorter code than deriving page_zone(end_page) */
+ if (page_zone_id(start_page) != page_zone_id(end_page))
+ return NULL;
+
+ return start_page;
+}
+
#ifdef CONFIG_COMPACTION
/* Returns true if the pageblock should be scanned for pages to isolate. */
static inline bool isolation_suitable(struct compact_control *cc,
*/
static void update_pageblock_skip(struct compact_control *cc,
struct page *page, unsigned long nr_isolated,
- bool set_unsuitable, bool migrate_scanner)
+ bool migrate_scanner)
{
struct zone *zone = cc->zone;
unsigned long pfn;
if (nr_isolated)
return;
- /*
- * Only skip pageblocks when all forms of compaction will be known to
- * fail in the near future.
- */
- if (set_unsuitable)
- set_pageblock_skip(page);
+ set_pageblock_skip(page);
pfn = page_to_pfn(page);
static void update_pageblock_skip(struct compact_control *cc,
struct page *page, unsigned long nr_isolated,
- bool set_unsuitable, bool migrate_scanner)
+ bool migrate_scanner)
{
}
#endif /* CONFIG_COMPACTION */
-static inline bool should_release_lock(spinlock_t *lock)
+/*
+ * Compaction requires the taking of some coarse locks that are potentially
+ * very heavily contended. For async compaction, back out if the lock cannot
+ * be taken immediately. For sync compaction, spin on the lock if needed.
+ *
+ * Returns true if the lock is held
+ * Returns false if the lock is not held and compaction should abort
+ */
+static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags,
+ struct compact_control *cc)
{
- return need_resched() || spin_is_contended(lock);
+ if (cc->mode == MIGRATE_ASYNC) {
+ if (!spin_trylock_irqsave(lock, *flags)) {
+ cc->contended = COMPACT_CONTENDED_LOCK;
+ return false;
+ }
+ } else {
+ spin_lock_irqsave(lock, *flags);
+ }
+
+ return true;
}
/*
* Compaction requires the taking of some coarse locks that are potentially
- * very heavily contended. Check if the process needs to be scheduled or
- * if the lock is contended. For async compaction, back out in the event
- * if contention is severe. For sync compaction, schedule.
+ * very heavily contended. The lock should be periodically unlocked to avoid
+ * having disabled IRQs for a long time, even when there is nobody waiting on
+ * the lock. It might also be that allowing the IRQs will result in
+ * need_resched() becoming true. If scheduling is needed, async compaction
+ * aborts. Sync compaction schedules.
+ * Either compaction type will also abort if a fatal signal is pending.
+ * In either case if the lock was locked, it is dropped and not regained.
*
- * Returns true if the lock is held.
- * Returns false if the lock is released and compaction should abort
+ * Returns true if compaction should abort due to fatal signal pending, or
+ * async compaction due to need_resched()
+ * Returns false when compaction can continue (sync compaction might have
+ * scheduled)
*/
-static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags,
- bool locked, struct compact_control *cc)
+static bool compact_unlock_should_abort(spinlock_t *lock,
+ unsigned long flags, bool *locked, struct compact_control *cc)
{
- if (should_release_lock(lock)) {
- if (locked) {
- spin_unlock_irqrestore(lock, *flags);
- locked = false;
- }
+ if (*locked) {
+ spin_unlock_irqrestore(lock, flags);
+ *locked = false;
+ }
+
+ if (fatal_signal_pending(current)) {
+ cc->contended = COMPACT_CONTENDED_SCHED;
+ return true;
+ }
- /* async aborts if taking too long or contended */
+ if (need_resched()) {
if (cc->mode == MIGRATE_ASYNC) {
- cc->contended = true;
- return false;
+ cc->contended = COMPACT_CONTENDED_SCHED;
+ return true;
}
-
cond_resched();
}
- if (!locked)
- spin_lock_irqsave(lock, *flags);
- return true;
+ return false;
}
/*
* Aside from avoiding lock contention, compaction also periodically checks
* need_resched() and either schedules in sync compaction or aborts async
- * compaction. This is similar to what compact_checklock_irqsave() does, but
+ * compaction. This is similar to what compact_unlock_should_abort() does, but
* is used where no lock is concerned.
*
* Returns false when no scheduling was needed, or sync compaction scheduled.
/* async compaction aborts if contended */
if (need_resched()) {
if (cc->mode == MIGRATE_ASYNC) {
- cc->contended = true;
+ cc->contended = COMPACT_CONTENDED_SCHED;
return true;
}
static bool suitable_migration_target(struct page *page)
{
/* If the page is a large free page, then disallow migration */
- if (PageBuddy(page) && page_order(page) >= pageblock_order)
- return false;
+ if (PageBuddy(page)) {
+ /*
+ * We are checking page_order without zone->lock taken. But
+ * the only small danger is that we skip a potentially suitable
+ * pageblock, so it's not worth to check order for valid range.
+ */
+ if (page_order_unsafe(page) >= pageblock_order)
+ return false;
+ }
/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
if (migrate_async_suitable(get_pageblock_migratetype(page)))
* (even though it may still end up isolating some pages).
*/
static unsigned long isolate_freepages_block(struct compact_control *cc,
- unsigned long blockpfn,
+ unsigned long *start_pfn,
unsigned long end_pfn,
struct list_head *freelist,
bool strict)
{
int nr_scanned = 0, total_isolated = 0;
struct page *cursor, *valid_page = NULL;
- unsigned long flags;
+ unsigned long flags = 0;
bool locked = false;
- bool checked_pageblock = false;
+ unsigned long blockpfn = *start_pfn;
cursor = pfn_to_page(blockpfn);
int isolated, i;
struct page *page = cursor;
+ /*
+ * Periodically drop the lock (if held) regardless of its
+ * contention, to give chance to IRQs. Abort if fatal signal
+ * pending or async compaction detects need_resched()
+ */
+ if (!(blockpfn % SWAP_CLUSTER_MAX)
+ && compact_unlock_should_abort(&cc->zone->lock, flags,
+ &locked, cc))
+ break;
+
nr_scanned++;
if (!pfn_valid_within(blockpfn))
goto isolate_fail;
goto isolate_fail;
/*
- * The zone lock must be held to isolate freepages.
- * Unfortunately this is a very coarse lock and can be
- * heavily contended if there are parallel allocations
- * or parallel compactions. For async compaction do not
- * spin on the lock and we acquire the lock as late as
- * possible.
+ * If we already hold the lock, we can skip some rechecking.
+ * Note that if we hold the lock now, checked_pageblock was
+ * already set in some previous iteration (or strict is true),
+ * so it is correct to skip the suitable migration target
+ * recheck as well.
*/
- locked = compact_checklock_irqsave(&cc->zone->lock, &flags,
- locked, cc);
- if (!locked)
- break;
-
- /* Recheck this is a suitable migration target under lock */
- if (!strict && !checked_pageblock) {
+ if (!locked) {
/*
- * We need to check suitability of pageblock only once
- * and this isolate_freepages_block() is called with
- * pageblock range, so just check once is sufficient.
+ * The zone lock must be held to isolate freepages.
+ * Unfortunately this is a very coarse lock and can be
+ * heavily contended if there are parallel allocations
+ * or parallel compactions. For async compaction do not
+ * spin on the lock and we acquire the lock as late as
+ * possible.
*/
- checked_pageblock = true;
- if (!suitable_migration_target(page))
+ locked = compact_trylock_irqsave(&cc->zone->lock,
+ &flags, cc);
+ if (!locked)
break;
- }
- /* Recheck this is a buddy page under lock */
- if (!PageBuddy(page))
- goto isolate_fail;
+ /* Recheck this is a buddy page under lock */
+ if (!PageBuddy(page))
+ goto isolate_fail;
+ }
/* Found a free page, break it into order-0 pages */
isolated = split_free_page(page);
}
+ /* Record how far we have got within the block */
+ *start_pfn = blockpfn;
+
trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated);
/*
/* Update the pageblock-skip if the whole pageblock was scanned */
if (blockpfn == end_pfn)
- update_pageblock_skip(cc, valid_page, total_isolated, true,
- false);
+ update_pageblock_skip(cc, valid_page, total_isolated, false);
count_compact_events(COMPACTFREE_SCANNED, nr_scanned);
if (total_isolated)
unsigned long isolated, pfn, block_end_pfn;
LIST_HEAD(freelist);
- for (pfn = start_pfn; pfn < end_pfn; pfn += isolated) {
- if (!pfn_valid(pfn) || cc->zone != page_zone(pfn_to_page(pfn)))
- break;
+ pfn = start_pfn;
+ block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
+
+ for (; pfn < end_pfn; pfn += isolated,
+ block_end_pfn += pageblock_nr_pages) {
+ /* Protect pfn from changing by isolate_freepages_block */
+ unsigned long isolate_start_pfn = pfn;
- /*
- * On subsequent iterations ALIGN() is actually not needed,
- * but we keep it that we not to complicate the code.
- */
- block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
block_end_pfn = min(block_end_pfn, end_pfn);
- isolated = isolate_freepages_block(cc, pfn, block_end_pfn,
- &freelist, true);
+ if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone))
+ break;
+
+ isolated = isolate_freepages_block(cc, &isolate_start_pfn,
+ block_end_pfn, &freelist, true);
/*
* In strict mode, isolate_freepages_block() returns 0 if
}
/* Update the number of anon and file isolated pages in the zone */
-static void acct_isolated(struct zone *zone, bool locked, struct compact_control *cc)
+static void acct_isolated(struct zone *zone, struct compact_control *cc)
{
struct page *page;
unsigned int count[2] = { 0, };
+ if (list_empty(&cc->migratepages))
+ return;
+
list_for_each_entry(page, &cc->migratepages, lru)
count[!!page_is_file_cache(page)]++;
- /* If locked we can use the interrupt unsafe versions */
- if (locked) {
- __mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
- __mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
- } else {
- mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
- mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
- }
+ mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
+ mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
}
/* Similar to reclaim, but different enough that they don't share logic */
}
/**
- * isolate_migratepages_range() - isolate all migrate-able pages in range.
- * @zone: Zone pages are in.
+ * isolate_migratepages_block() - isolate all migrate-able pages within
+ * a single pageblock
* @cc: Compaction control structure.
- * @low_pfn: The first PFN of the range.
- * @end_pfn: The one-past-the-last PFN of the range.
- * @unevictable: true if it allows to isolate unevictable pages
+ * @low_pfn: The first PFN to isolate
+ * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
+ * @isolate_mode: Isolation mode to be used.
*
* Isolate all pages that can be migrated from the range specified by
- * [low_pfn, end_pfn). Returns zero if there is a fatal signal
- * pending), otherwise PFN of the first page that was not scanned
- * (which may be both less, equal to or more then end_pfn).
+ * [low_pfn, end_pfn). The range is expected to be within same pageblock.
+ * Returns zero if there is a fatal signal pending, otherwise PFN of the
+ * first page that was not scanned (which may be both less, equal to or more
+ * than end_pfn).
*
- * Assumes that cc->migratepages is empty and cc->nr_migratepages is
- * zero.
- *
- * Apart from cc->migratepages and cc->nr_migratetypes this function
- * does not modify any cc's fields, in particular it does not modify
- * (or read for that matter) cc->migrate_pfn.
+ * The pages are isolated on cc->migratepages list (not required to be empty),
+ * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
+ * is neither read nor updated.
*/
-unsigned long
-isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
- unsigned long low_pfn, unsigned long end_pfn, bool unevictable)
+static unsigned long
+isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
+ unsigned long end_pfn, isolate_mode_t isolate_mode)
{
- unsigned long last_pageblock_nr = 0, pageblock_nr;
+ struct zone *zone = cc->zone;
unsigned long nr_scanned = 0, nr_isolated = 0;
struct list_head *migratelist = &cc->migratepages;
struct lruvec *lruvec;
- unsigned long flags;
+ unsigned long flags = 0;
bool locked = false;
struct page *page = NULL, *valid_page = NULL;
- bool set_unsuitable = true;
- const isolate_mode_t mode = (cc->mode == MIGRATE_ASYNC ?
- ISOLATE_ASYNC_MIGRATE : 0) |
- (unevictable ? ISOLATE_UNEVICTABLE : 0);
/*
* Ensure that there are not too many pages isolated from the LRU
/* Time to isolate some pages for migration */
for (; low_pfn < end_pfn; low_pfn++) {
- /* give a chance to irqs before checking need_resched() */
- if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) {
- if (should_release_lock(&zone->lru_lock)) {
- spin_unlock_irqrestore(&zone->lru_lock, flags);
- locked = false;
- }
- }
-
/*
- * migrate_pfn does not necessarily start aligned to a
- * pageblock. Ensure that pfn_valid is called when moving
- * into a new MAX_ORDER_NR_PAGES range in case of large
- * memory holes within the zone
+ * Periodically drop the lock (if held) regardless of its
+ * contention, to give chance to IRQs. Abort async compaction
+ * if contended.
*/
- if ((low_pfn & (MAX_ORDER_NR_PAGES - 1)) == 0) {
- if (!pfn_valid(low_pfn)) {
- low_pfn += MAX_ORDER_NR_PAGES - 1;
- continue;
- }
- }
+ if (!(low_pfn % SWAP_CLUSTER_MAX)
+ && compact_unlock_should_abort(&zone->lru_lock, flags,
+ &locked, cc))
+ break;
if (!pfn_valid_within(low_pfn))
continue;
nr_scanned++;
- /*
- * Get the page and ensure the page is within the same zone.
- * See the comment in isolate_freepages about overlapping
- * nodes. It is deliberate that the new zone lock is not taken
- * as memory compaction should not move pages between nodes.
- */
page = pfn_to_page(low_pfn);
- if (page_zone(page) != zone)
- continue;
if (!valid_page)
valid_page = page;
- /* If isolation recently failed, do not retry */
- pageblock_nr = low_pfn >> pageblock_order;
- if (last_pageblock_nr != pageblock_nr) {
- int mt;
-
- last_pageblock_nr = pageblock_nr;
- if (!isolation_suitable(cc, page))
- goto next_pageblock;
+ /*
+ * Skip if free. We read page order here without zone lock
+ * which is generally unsafe, but the race window is small and
+ * the worst thing that can happen is that we skip some
+ * potential isolation targets.
+ */
+ if (PageBuddy(page)) {
+ unsigned long freepage_order = page_order_unsafe(page);
/*
- * For async migration, also only scan in MOVABLE
- * blocks. Async migration is optimistic to see if
- * the minimum amount of work satisfies the allocation
+ * Without lock, we cannot be sure that what we got is
+ * a valid page order. Consider only values in the
+ * valid order range to prevent low_pfn overflow.
*/
- mt = get_pageblock_migratetype(page);
- if (cc->mode == MIGRATE_ASYNC &&
- !migrate_async_suitable(mt)) {
- set_unsuitable = false;
- goto next_pageblock;
- }
- }
-
- /*
- * Skip if free. page_order cannot be used without zone->lock
- * as nothing prevents parallel allocations or buddy merging.
- */
- if (PageBuddy(page))
+ if (freepage_order > 0 && freepage_order < MAX_ORDER)
+ low_pfn += (1UL << freepage_order) - 1;
continue;
+ }
/*
* Check may be lockless but that's ok as we recheck later.
*/
if (!PageLRU(page)) {
if (unlikely(balloon_page_movable(page))) {
- if (locked && balloon_page_isolate(page)) {
+ if (balloon_page_isolate(page)) {
/* Successfully isolated */
goto isolate_success;
}
*/
if (PageTransHuge(page)) {
if (!locked)
- goto next_pageblock;
- low_pfn += (1 << compound_order(page)) - 1;
+ low_pfn = ALIGN(low_pfn + 1,
+ pageblock_nr_pages) - 1;
+ else
+ low_pfn += (1 << compound_order(page)) - 1;
+
continue;
}
page_count(page) > page_mapcount(page))
continue;
- /* Check if it is ok to still hold the lock */
- locked = compact_checklock_irqsave(&zone->lru_lock, &flags,
- locked, cc);
- if (!locked || fatal_signal_pending(current))
- break;
+ /* If we already hold the lock, we can skip some rechecking */
+ if (!locked) {
+ locked = compact_trylock_irqsave(&zone->lru_lock,
+ &flags, cc);
+ if (!locked)
+ break;
- /* Recheck PageLRU and PageTransHuge under lock */
- if (!PageLRU(page))
- continue;
- if (PageTransHuge(page)) {
- low_pfn += (1 << compound_order(page)) - 1;
- continue;
+ /* Recheck PageLRU and PageTransHuge under lock */
+ if (!PageLRU(page))
+ continue;
+ if (PageTransHuge(page)) {
+ low_pfn += (1 << compound_order(page)) - 1;
+ continue;
+ }
}
lruvec = mem_cgroup_page_lruvec(page, zone);
/* Try isolate the page */
- if (__isolate_lru_page(page, mode) != 0)
+ if (__isolate_lru_page(page, isolate_mode) != 0)
continue;
VM_BUG_ON_PAGE(PageTransCompound(page), page);
++low_pfn;
break;
}
-
- continue;
-
-next_pageblock:
- low_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages) - 1;
}
- acct_isolated(zone, locked, cc);
+ /*
+ * The PageBuddy() check could have potentially brought us outside
+ * the range to be scanned.
+ */
+ if (unlikely(low_pfn > end_pfn))
+ low_pfn = end_pfn;
if (locked)
spin_unlock_irqrestore(&zone->lru_lock, flags);
* if the whole pageblock was scanned without isolating any page.
*/
if (low_pfn == end_pfn)
- update_pageblock_skip(cc, valid_page, nr_isolated,
- set_unsuitable, true);
+ update_pageblock_skip(cc, valid_page, nr_isolated, true);
trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
return low_pfn;
}
+/**
+ * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
+ * @cc: Compaction control structure.
+ * @start_pfn: The first PFN to start isolating.
+ * @end_pfn: The one-past-last PFN.
+ *
+ * Returns zero if isolation fails fatally due to e.g. pending signal.
+ * Otherwise, function returns one-past-the-last PFN of isolated page
+ * (which may be greater than end_pfn if end fell in a middle of a THP page).
+ */
+unsigned long
+isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
+ unsigned long end_pfn)
+{
+ unsigned long pfn, block_end_pfn;
+
+ /* Scan block by block. First and last block may be incomplete */
+ pfn = start_pfn;
+ block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
+
+ for (; pfn < end_pfn; pfn = block_end_pfn,
+ block_end_pfn += pageblock_nr_pages) {
+
+ block_end_pfn = min(block_end_pfn, end_pfn);
+
+ if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone))
+ continue;
+
+ pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
+ ISOLATE_UNEVICTABLE);
+
+ /*
+ * In case of fatal failure, release everything that might
+ * have been isolated in the previous iteration, and signal
+ * the failure back to caller.
+ */
+ if (!pfn) {
+ putback_movable_pages(&cc->migratepages);
+ cc->nr_migratepages = 0;
+ break;
+ }
+ }
+ acct_isolated(cc->zone, cc);
+
+ return pfn;
+}
+
#endif /* CONFIG_COMPACTION || CONFIG_CMA */
#ifdef CONFIG_COMPACTION
/*
* Based on information in the current compact_control, find blocks
* suitable for isolating free pages from and then isolate them.
*/
-static void isolate_freepages(struct zone *zone,
- struct compact_control *cc)
+static void isolate_freepages(struct compact_control *cc)
{
+ struct zone *zone = cc->zone;
struct page *page;
unsigned long block_start_pfn; /* start of current pageblock */
+ unsigned long isolate_start_pfn; /* exact pfn we start at */
unsigned long block_end_pfn; /* end of current pageblock */
unsigned long low_pfn; /* lowest pfn scanner is able to scan */
int nr_freepages = cc->nr_freepages;
/*
* Initialise the free scanner. The starting point is where we last
* successfully isolated from, zone-cached value, or the end of the
- * zone when isolating for the first time. We need this aligned to
- * the pageblock boundary, because we do
+ * zone when isolating for the first time. For looping we also need
+ * this pfn aligned down to the pageblock boundary, because we do
* block_start_pfn -= pageblock_nr_pages in the for loop.
* For ending point, take care when isolating in last pageblock of a
* a zone which ends in the middle of a pageblock.
* The low boundary is the end of the pageblock the migration scanner
* is using.
*/
+ isolate_start_pfn = cc->free_pfn;
block_start_pfn = cc->free_pfn & ~(pageblock_nr_pages-1);
block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
zone_end_pfn(zone));
*/
for (; block_start_pfn >= low_pfn && cc->nr_migratepages > nr_freepages;
block_end_pfn = block_start_pfn,
- block_start_pfn -= pageblock_nr_pages) {
+ block_start_pfn -= pageblock_nr_pages,
+ isolate_start_pfn = block_start_pfn) {
unsigned long isolated;
/*
&& compact_should_abort(cc))
break;
- if (!pfn_valid(block_start_pfn))
- continue;
-
- /*
- * Check for overlapping nodes/zones. It's possible on some
- * configurations to have a setup like
- * node0 node1 node0
- * i.e. it's possible that all pages within a zones range of
- * pages do not belong to a single zone.
- */
- page = pfn_to_page(block_start_pfn);
- if (page_zone(page) != zone)
+ page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
+ zone);
+ if (!page)
continue;
/* Check the block is suitable for migration */
if (!isolation_suitable(cc, page))
continue;
- /* Found a block suitable for isolating free pages from */
- cc->free_pfn = block_start_pfn;
- isolated = isolate_freepages_block(cc, block_start_pfn,
+ /* Found a block suitable for isolating free pages from. */
+ isolated = isolate_freepages_block(cc, &isolate_start_pfn,
block_end_pfn, freelist, false);
nr_freepages += isolated;
+ /*
+ * Remember where the free scanner should restart next time,
+ * which is where isolate_freepages_block() left off.
+ * But if it scanned the whole pageblock, isolate_start_pfn
+ * now points at block_end_pfn, which is the start of the next
+ * pageblock.
+ * In that case we will however want to restart at the start
+ * of the previous pageblock.
+ */
+ cc->free_pfn = (isolate_start_pfn < block_end_pfn) ?
+ isolate_start_pfn :
+ block_start_pfn - pageblock_nr_pages;
+
/*
* Set a flag that we successfully isolated in this pageblock.
* In the next loop iteration, zone->compact_cached_free_pfn
*/
if (list_empty(&cc->freepages)) {
if (!cc->contended)
- isolate_freepages(cc->zone, cc);
+ isolate_freepages(cc);
if (list_empty(&cc->freepages))
return NULL;
} isolate_migrate_t;
/*
- * Isolate all pages that can be migrated from the block pointed to by
- * the migrate scanner within compact_control.
+ * Isolate all pages that can be migrated from the first suitable block,
+ * starting at the block pointed to by the migrate scanner pfn within
+ * compact_control.
*/
static isolate_migrate_t isolate_migratepages(struct zone *zone,
struct compact_control *cc)
{
unsigned long low_pfn, end_pfn;
+ struct page *page;
+ const isolate_mode_t isolate_mode =
+ (cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0);
- /* Do not scan outside zone boundaries */
- low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
+ /*
+ * Start at where we last stopped, or beginning of the zone as
+ * initialized by compact_zone()
+ */
+ low_pfn = cc->migrate_pfn;
/* Only scan within a pageblock boundary */
end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages);
- /* Do not cross the free scanner or scan within a memory hole */
- if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
- cc->migrate_pfn = end_pfn;
- return ISOLATE_NONE;
- }
+ /*
+ * Iterate over whole pageblocks until we find the first suitable.
+ * Do not cross the free scanner.
+ */
+ for (; end_pfn <= cc->free_pfn;
+ low_pfn = end_pfn, end_pfn += pageblock_nr_pages) {
- /* Perform the isolation */
- low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn, false);
- if (!low_pfn || cc->contended)
- return ISOLATE_ABORT;
+ /*
+ * This can potentially iterate a massively long zone with
+ * many pageblocks unsuitable, so periodically check if we
+ * need to schedule, or even abort async compaction.
+ */
+ if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
+ && compact_should_abort(cc))
+ break;
+
+ page = pageblock_pfn_to_page(low_pfn, end_pfn, zone);
+ if (!page)
+ continue;
+
+ /* If isolation recently failed, do not retry */
+ if (!isolation_suitable(cc, page))
+ continue;
+
+ /*
+ * For async compaction, also only scan in MOVABLE blocks.
+ * Async compaction is optimistic to see if the minimum amount
+ * of work satisfies the allocation.
+ */
+ if (cc->mode == MIGRATE_ASYNC &&
+ !migrate_async_suitable(get_pageblock_migratetype(page)))
+ continue;
+
+ /* Perform the isolation */
+ low_pfn = isolate_migratepages_block(cc, low_pfn, end_pfn,
+ isolate_mode);
+ if (!low_pfn || cc->contended)
+ return ISOLATE_ABORT;
+
+ /*
+ * Either we isolated something and proceed with migration. Or
+ * we failed and compact_zone should decide if we should
+ * continue or not.
+ */
+ break;
+ }
+
+ acct_isolated(zone, cc);
+ /* Record where migration scanner will be restarted */
cc->migrate_pfn = low_pfn;
- return ISOLATE_SUCCESS;
+ return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
}
-static int compact_finished(struct zone *zone,
- struct compact_control *cc)
+static int compact_finished(struct zone *zone, struct compact_control *cc,
+ const int migratetype)
{
unsigned int order;
unsigned long watermark;
struct free_area *area = &zone->free_area[order];
/* Job done if page is free of the right migratetype */
- if (!list_empty(&area->free_list[cc->migratetype]))
+ if (!list_empty(&area->free_list[migratetype]))
return COMPACT_PARTIAL;
/* Job done if allocation would set block type */
int ret;
unsigned long start_pfn = zone->zone_start_pfn;
unsigned long end_pfn = zone_end_pfn(zone);
+ const int migratetype = gfpflags_to_migratetype(cc->gfp_mask);
const bool sync = cc->mode != MIGRATE_ASYNC;
ret = compaction_suitable(zone, cc->order);
migrate_prep_local();
- while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
+ while ((ret = compact_finished(zone, cc, migratetype)) ==
+ COMPACT_CONTINUE) {
int err;
switch (isolate_migratepages(zone, cc)) {
;
}
- if (!cc->nr_migratepages)
- continue;
-
err = migrate_pages(&cc->migratepages, compaction_alloc,
compaction_free, (unsigned long)cc, cc->mode,
MR_COMPACTION);
}
static unsigned long compact_zone_order(struct zone *zone, int order,
- gfp_t gfp_mask, enum migrate_mode mode, bool *contended)
+ gfp_t gfp_mask, enum migrate_mode mode, int *contended)
{
unsigned long ret;
struct compact_control cc = {
.nr_freepages = 0,
.nr_migratepages = 0,
.order = order,
- .migratetype = allocflags_to_migratetype(gfp_mask),
+ .gfp_mask = gfp_mask,
.zone = zone,
.mode = mode,
};
* @gfp_mask: The GFP mask of the current allocation
* @nodemask: The allowed nodes to allocate from
* @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
+ * @contended: Return value that determines if compaction was aborted due to
+ * need_resched() or lock contention
+ * @candidate_zone: Return the zone where we think allocation should succeed
*
* This is the main entry point for direct page compaction.
*/
unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *nodemask,
- enum migrate_mode mode, bool *contended)
+ enum migrate_mode mode, int *contended,
+ struct zone **candidate_zone)
{
enum zone_type high_zoneidx = gfp_zone(gfp_mask);
int may_enter_fs = gfp_mask & __GFP_FS;
int may_perform_io = gfp_mask & __GFP_IO;
struct zoneref *z;
struct zone *zone;
- int rc = COMPACT_SKIPPED;
+ int rc = COMPACT_DEFERRED;
int alloc_flags = 0;
+ int all_zones_contended = COMPACT_CONTENDED_LOCK; /* init for &= op */
+
+ *contended = COMPACT_CONTENDED_NONE;
/* Check if the GFP flags allow compaction */
if (!order || !may_enter_fs || !may_perform_io)
- return rc;
-
- count_compact_event(COMPACTSTALL);
+ return COMPACT_SKIPPED;
#ifdef CONFIG_CMA
- if (allocflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
+ if (gfpflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
alloc_flags |= ALLOC_CMA;
#endif
/* Compact each zone in the list */
for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
nodemask) {
int status;
+ int zone_contended;
+
+ if (compaction_deferred(zone, order))
+ continue;
status = compact_zone_order(zone, order, gfp_mask, mode,
- contended);
+ &zone_contended);
rc = max(status, rc);
+ /*
+ * It takes at least one zone that wasn't lock contended
+ * to clear all_zones_contended.
+ */
+ all_zones_contended &= zone_contended;
/* If a normal allocation would succeed, stop compacting */
if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0,
- alloc_flags))
- break;
+ alloc_flags)) {
+ *candidate_zone = zone;
+ /*
+ * We think the allocation will succeed in this zone,
+ * but it is not certain, hence the false. The caller
+ * will repeat this with true if allocation indeed
+ * succeeds in this zone.
+ */
+ compaction_defer_reset(zone, order, false);
+ /*
+ * It is possible that async compaction aborted due to
+ * need_resched() and the watermarks were ok thanks to
+ * somebody else freeing memory. The allocation can
+ * however still fail so we better signal the
+ * need_resched() contention anyway (this will not
+ * prevent the allocation attempt).
+ */
+ if (zone_contended == COMPACT_CONTENDED_SCHED)
+ *contended = COMPACT_CONTENDED_SCHED;
+
+ goto break_loop;
+ }
+
+ if (mode != MIGRATE_ASYNC) {
+ /*
+ * We think that allocation won't succeed in this zone
+ * so we defer compaction there. If it ends up
+ * succeeding after all, it will be reset.
+ */
+ defer_compaction(zone, order);
+ }
+
+ /*
+ * We might have stopped compacting due to need_resched() in
+ * async compaction, or due to a fatal signal detected. In that
+ * case do not try further zones and signal need_resched()
+ * contention.
+ */
+ if ((zone_contended == COMPACT_CONTENDED_SCHED)
+ || fatal_signal_pending(current)) {
+ *contended = COMPACT_CONTENDED_SCHED;
+ goto break_loop;
+ }
+
+ continue;
+break_loop:
+ /*
+ * We might not have tried all the zones, so be conservative
+ * and assume they are not all lock contended.
+ */
+ all_zones_contended = 0;
+ break;
}
+ /*
+ * If at least one zone wasn't deferred or skipped, we report if all
+ * zones that were tried were lock contended.
+ */
+ if (rc > COMPACT_SKIPPED && all_zones_contended)
+ *contended = COMPACT_CONTENDED_LOCK;
+
return rc;
}
projects / cascardo / linux.git / blobdiff