Function cache_free

freebsd/vm/uma_core.c:4407–4495

* Populate a free or cross bucket for the current cpu cache. Free any * existing full bucket either to the zone cache or back to the slab layer. * * Enters and returns in a critical section. false return indicates that * we can not satisfy this free in the cache layer. true indicates that * the caller should retry. */

 * the caller should retry.
 */
static __noinline bool
cache_free(uma_zone_t zone, uma_cache_t cache, void *udata, void *item,
    int itemdomain)
{
	uma_cache_bucket_t cbucket;
	uma_bucket_t newbucket, bucket;

	CRITICAL_ASSERT(curthread);

	if (zone->uz_bucket_size == 0)
		return false;

	cache = &zone->uz_cpu[curcpu];
	newbucket = NULL;

	/*
	 * FIRSTTOUCH domains need to free to the correct zdom.  When
	 * enabled this is the zdom of the item.   The bucket is the
	 * cross bucket if the current domain and itemdomain do not match.
	 */
	cbucket = &cache->uc_freebucket;
#ifdef NUMA
	if ((cache_uz_flags(cache) & UMA_ZONE_FIRSTTOUCH) != 0) {
		if (PCPU_GET(domain) != itemdomain) {
			cbucket = &cache->uc_crossbucket;
			if (cbucket->ucb_cnt != 0)
				counter_u64_add(zone->uz_xdomain,
				    cbucket->ucb_cnt);
		}
	}
#endif
	bucket = cache_bucket_unload(cbucket);
	KASSERT(bucket == NULL || bucket->ub_cnt == bucket->ub_entries,
	    ("cache_free: Entered with non-full free bucket."));

	/* We are no longer associated with this CPU. */
	critical_exit();

	/*
	 * Don't let SMR zones operate without a free bucket.  Force
	 * a synchronize and re-use this one.  We will only degrade
	 * to a synchronize every bucket_size items rather than every
	 * item if we fail to allocate a bucket.
	 */
	if ((zone->uz_flags & UMA_ZONE_SMR) != 0) {
		if (bucket != NULL)
			bucket->ub_seq = smr_advance(zone->uz_smr);
		newbucket = bucket_alloc(zone, udata, M_NOWAIT);
		if (newbucket == NULL && bucket != NULL) {
			bucket_drain(zone, bucket);
			newbucket = bucket;
			bucket = NULL;
		}
	} else if (!bucketdisable)
		newbucket = bucket_alloc(zone, udata, M_NOWAIT);

	if (bucket != NULL)
		zone_free_bucket(zone, bucket, udata, itemdomain, true);