Function zone_free_cross

freebsd/vm/uma_core.c:4282–4365

* sort crossdomain free buckets to domain correct buckets and cache * them. */

 * them.
 */
static void
zone_free_cross(uma_zone_t zone, uma_bucket_t bucket, void *udata)
{
	struct uma_bucketlist emptybuckets, fullbuckets;
	uma_zone_domain_t zdom;
	uma_bucket_t b;
	smr_seq_t seq;
	void *item;
	int domain;

	CTR3(KTR_UMA,
	    "uma_zfree: zone %s(%p) draining cross bucket %p",
	    zone->uz_name, zone, bucket);

	/*
	 * It is possible for buckets to arrive here out of order so we fetch
	 * the current smr seq rather than accepting the bucket's.
	 */
	seq = SMR_SEQ_INVALID;
	if ((zone->uz_flags & UMA_ZONE_SMR) != 0)
		seq = smr_advance(zone->uz_smr);

	/*
	 * To avoid having ndomain * ndomain buckets for sorting we have a
	 * lock on the current crossfree bucket.  A full matrix with
	 * per-domain locking could be used if necessary.
	 */
	STAILQ_INIT(&emptybuckets);
	STAILQ_INIT(&fullbuckets);
	ZONE_CROSS_LOCK(zone);
	for (; bucket->ub_cnt > 0; bucket->ub_cnt--) {
		item = bucket->ub_bucket[bucket->ub_cnt - 1];
		domain = item_domain(item);
		zdom = ZDOM_GET(zone, domain);
		if (zdom->uzd_cross == NULL) {
			if ((b = STAILQ_FIRST(&emptybuckets)) != NULL) {
				STAILQ_REMOVE_HEAD(&emptybuckets, ub_link);
				zdom->uzd_cross = b;
			} else {
				/*
				 * Avoid allocating a bucket with the cross lock
				 * held, since allocation can trigger a
				 * cross-domain free and bucket zones may
				 * allocate from each other.
				 */
				ZONE_CROSS_UNLOCK(zone);
				b = bucket_alloc(zone, udata, M_NOWAIT);
				if (b == NULL)
					goto out;
				ZONE_CROSS_LOCK(zone);
				if (zdom->uzd_cross != NULL) {
					STAILQ_INSERT_HEAD(&emptybuckets, b,
					    ub_link);
				} else {
					zdom->uzd_cross = b;
				}
			}
		}