Commit 79cd674a authored by Chengguang Xu's avatar Chengguang Xu Committed by Ilya Dryomov
Browse files

ceph: optimizing cap reservation 



When caps_avail_count is in a low level, most newly
trimmed caps will probably go into ->caps_list and
caps_avail_count will be increased. Hence after trimming,
should recheck caps_avail_count to effectly reuse
newly trimmed caps. Also, when releasing unnecessary
caps follow the same rule of ceph_put_cap.

Signed-off-by: default avatarChengguang Xu <cgxu519@icloud.com>
Reviewed-by: default avatar"Yan, Zheng" <zyan@redhat.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent b517c1d8

fs/ceph/caps.c

+59 −29
Original line number Diff line number Diff line
@@ -184,10 +184,15 @@ int ceph_reserve_caps(struct ceph_mds_client *mdsc, 
					 mdsc->caps_avail_count);

	spin_unlock(&mdsc->caps_list_lock);



	for (i = have; i < need; i++) {

retry:

	for (i = have; i < need; ) {

		cap = kmem_cache_alloc(ceph_cap_cachep, GFP_NOFS);

		if (!cap) {

		if (cap) {

			list_add(&cap->caps_item, &newcaps);

			alloc++;

			i++;

			continue;

		}



		if (!trimmed) {

			for (j = 0; j < mdsc->max_sessions; j++) {

				s = __ceph_lookup_mds_session(mdsc, j);
@@ -204,16 +209,29 @@ retry: 
				mutex_lock(&mdsc->mutex);

			}

			trimmed = true;

				goto retry;

			} else {

				pr_warn("reserve caps ctx=%p ENOMEM "

					"need=%d got=%d\n",

					ctx, need, have + alloc);

				goto out_nomem;



			spin_lock(&mdsc->caps_list_lock);

			if (mdsc->caps_avail_count) {

				int more_have;

				if (mdsc->caps_avail_count >= need - i)

					more_have = need - i;

				else

					more_have = mdsc->caps_avail_count;



				i += more_have;

				have += more_have;

				mdsc->caps_avail_count -= more_have;

				mdsc->caps_reserve_count += more_have;



			}

			spin_unlock(&mdsc->caps_list_lock);



			continue;

		}

		list_add(&cap->caps_item, &newcaps);

		alloc++;



		pr_warn("reserve caps ctx=%p ENOMEM need=%d got=%d\n",

			ctx, need, have + alloc);

		goto out_nomem;

	}

	BUG_ON(have + alloc != need);
@@ -234,16 +252,28 @@ retry: 
	return 0;



out_nomem:



	spin_lock(&mdsc->caps_list_lock);

	mdsc->caps_avail_count += have;

	mdsc->caps_reserve_count -= have;



	while (!list_empty(&newcaps)) {

		cap = list_first_entry(&newcaps,

				struct ceph_cap, caps_item);

		list_del(&cap->caps_item);



		/* Keep some preallocated caps around (ceph_min_count), to

		 * avoid lots of free/alloc churn. */

		if (mdsc->caps_avail_count >=

		    mdsc->caps_reserve_count + mdsc->caps_min_count) {

			kmem_cache_free(ceph_cap_cachep, cap);

		} else {

			mdsc->caps_avail_count++;

			mdsc->caps_total_count++;

			list_add(&cap->caps_item, &mdsc->caps_list);

		}

	}



	spin_lock(&mdsc->caps_list_lock);

	mdsc->caps_avail_count += have;

	mdsc->caps_reserve_count -= have;

	BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +

					 mdsc->caps_reserve_count +

					 mdsc->caps_avail_count);

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