diff options
| -rw-r--r-- | mm/page_alloc.c | 41 |
1 files changed, 32 insertions, 9 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 8d4335779633..eaaef2a09424 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4035,12 +4035,37 @@ static int __meminit zone_batchsize(struct zone *zone) #endif } +/* + * pcp->high and pcp->batch values are related and dependent on one another: + * ->batch must never be higher then ->high. + * The following function updates them in a safe manner without read side + * locking. + * + * Any new users of pcp->batch and pcp->high should ensure they can cope with + * those fields changing asynchronously (acording the the above rule). + * + * mutex_is_locked(&pcp_batch_high_lock) required when calling this function + * outside of boot time (or some other assurance that no concurrent updaters + * exist). + */ +static void pageset_update(struct per_cpu_pages *pcp, unsigned long high, + unsigned long batch) +{ + /* start with a fail safe value for batch */ + pcp->batch = 1; + smp_wmb(); + + /* Update high, then batch, in order */ + pcp->high = high; + smp_wmb(); + + pcp->batch = batch; +} + /* a companion to setup_pagelist_highmark() */ static void pageset_set_batch(struct per_cpu_pageset *p, unsigned long batch) { - struct per_cpu_pages *pcp = &p->pcp; - pcp->high = 6 * batch; - pcp->batch = max(1UL, 1 * batch); + pageset_update(&p->pcp, 6 * batch, max(1UL, 1 * batch)); } static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch) @@ -4064,13 +4089,11 @@ static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch) static void setup_pagelist_highmark(struct per_cpu_pageset *p, unsigned long high) { - struct per_cpu_pages *pcp; + unsigned long batch = max(1UL, high / 4); + if ((high / 4) > (PAGE_SHIFT * 8)) + batch = PAGE_SHIFT * 8; - pcp = &p->pcp; - pcp->high = high; - pcp->batch = max(1UL, high/4); - if ((high/4) > (PAGE_SHIFT * 8)) - pcp->batch = PAGE_SHIFT * 8; + pageset_update(&p->pcp, high, batch); } static void __meminit setup_zone_pageset(struct zone *zone) |