diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/compaction.c | 119 |
1 files changed, 72 insertions, 47 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 26bb20e..74770e4 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -223,61 +223,72 @@ static void update_pageblock_skip(struct compact_control *cc, } #endif /* CONFIG_COMPACTION */ -static int 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) { - /* - * Sched contention has higher priority here as we may potentially - * have to abort whole compaction ASAP. Returning with lock contention - * means we will try another zone, and further decisions are - * influenced only when all zones are lock contended. That means - * potentially missing a lock contention is less critical. - */ - if (need_resched()) - return COMPACT_CONTENDED_SCHED; - else if (spin_is_contended(lock)) - return COMPACT_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 COMPACT_CONTENDED_NONE; + 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) { - int contended = should_release_lock(lock); + if (*locked) { + spin_unlock_irqrestore(lock, flags); + *locked = false; + } - if (contended) { - 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 = contended; - 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. @@ -336,6 +347,16 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, 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; @@ -353,8 +374,9 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, * spin on the lock and we acquire the lock as late as * possible. */ - locked = compact_checklock_irqsave(&cc->zone->lock, &flags, - locked, cc); + if (!locked) + locked = compact_trylock_irqsave(&cc->zone->lock, + &flags, cc); if (!locked) break; @@ -552,13 +574,15 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, /* 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; - } - } + /* + * Periodically drop the lock (if held) regardless of its + * contention, to give chance to IRQs. Abort async compaction + * if contended. + */ + if (!(low_pfn % SWAP_CLUSTER_MAX) + && compact_unlock_should_abort(&zone->lru_lock, flags, + &locked, cc)) + break; if (!pfn_valid_within(low_pfn)) continue; @@ -620,10 +644,11 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, 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)) + /* If the lock is not held, try to take it */ + if (!locked) + locked = compact_trylock_irqsave(&zone->lru_lock, + &flags, cc); + if (!locked) break; /* Recheck PageLRU and PageTransHuge under lock */ |
