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MFC r258340, r258497:

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Implement mechanism to safely but slowly purge UMA per-CPU caches.

This is a last resort for very low memory condition in case other measures
to free memory were ineffective.  Sequentially cycle through all CPUs and
extract per-CPU cache buckets into zone cache from where they can be freed.
This commit is contained in:
mav 2014-01-04 23:39:39 +00:00
parent 4f2347ab59
commit 3ff6064c46
1 changed files with 89 additions and 0 deletions
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89
sys/vm/uma_core.c
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@ -75,6 +75,7 @@ __FBSDID("$FreeBSD$");
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/sbuf.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/vmmeter.h>
@ -685,6 +686,90 @@ cache_drain(uma_zone_t zone)
ZONE_UNLOCK(zone);
}
static void
cache_shrink(uma_zone_t zone)
{
if (zone->uz_flags & UMA_ZFLAG_INTERNAL)
return;
ZONE_LOCK(zone);
zone->uz_count = (zone->uz_count_min + zone->uz_count) / 2;
ZONE_UNLOCK(zone);
}
static void
cache_drain_safe_cpu(uma_zone_t zone)
{
uma_cache_t cache;
uma_bucket_t b1, b2;
if (zone->uz_flags & UMA_ZFLAG_INTERNAL)
return;
b1 = b2 = NULL;
ZONE_LOCK(zone);
critical_enter();
cache = &zone->uz_cpu[curcpu];
if (cache->uc_allocbucket) {
if (cache->uc_allocbucket->ub_cnt != 0)
LIST_INSERT_HEAD(&zone->uz_buckets,
cache->uc_allocbucket, ub_link);
else
b1 = cache->uc_allocbucket;
cache->uc_allocbucket = NULL;
}
if (cache->uc_freebucket) {
if (cache->uc_freebucket->ub_cnt != 0)
LIST_INSERT_HEAD(&zone->uz_buckets,
cache->uc_freebucket, ub_link);
else
b2 = cache->uc_freebucket;
cache->uc_freebucket = NULL;
}
critical_exit();
ZONE_UNLOCK(zone);
if (b1)
bucket_free(zone, b1, NULL);
if (b2)
bucket_free(zone, b2, NULL);
}
/*
* Safely drain per-CPU caches of a zone(s) to alloc bucket.
* This is an expensive call because it needs to bind to all CPUs
* one by one and enter a critical section on each of them in order
* to safely access their cache buckets.
* Zone lock must not be held on call this function.
*/
static void
cache_drain_safe(uma_zone_t zone)
{
int cpu;
/*
* Polite bucket sizes shrinking was not enouth, shrink aggressively.
*/
if (zone)
cache_shrink(zone);
else
zone_foreach(cache_shrink);
CPU_FOREACH(cpu) {
thread_lock(curthread);
sched_bind(curthread, cpu);
thread_unlock(curthread);
if (zone)
cache_drain_safe_cpu(zone);
else
zone_foreach(cache_drain_safe_cpu);
}
thread_lock(curthread);
sched_unbind(curthread);
thread_unlock(curthread);
}
/*
* Drain the cached buckets from a zone. Expects a locked zone on entry.
*/
@ -3070,6 +3155,10 @@ uma_reclaim(void)
#endif
bucket_enable();
zone_foreach(zone_drain);
if (vm_page_count_min()) {
cache_drain_safe(NULL);
zone_foreach(zone_drain);
}
/*
* Some slabs may have been freed but this zone will be visited early
* we visit again so that we can free pages that are empty once other