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List:       ceph-devel
Subject:    [PATCH] ceph: optimizing cap allocation
From:       Chengguang Xu <cgxu519 () icloud ! com>
Date:       2018-02-24 10:35:29
Message-ID: 1519468529-67956-1-git-send-email-cgxu519 () icloud ! com
[Download RAW message or body]

When setting high volume of caps_min_count or having many
unreserved caps, unused caps may always keep in the ->caps_list
even can't get new cap from kmem_cache_alloc because lack of
maximum limitation of caps_avail_count. Hence reuse caps in
->caps_list if available, it's maybe better than setting max
limitation of caps_avail_count and releasing unused caps when
reaching the limit.

Signed-off-by: Chengguang Xu <cgxu519@icloud.com>
---
Only compile tested.

 fs/ceph/caps.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 6582c45..b598a24 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -280,6 +280,23 @@ struct ceph_cap *ceph_get_cap(struct ceph_mds_client *mdsc,
 	/* temporary, until we do something about cap import/export */
 	if (!ctx) {
 		cap = kmem_cache_alloc(ceph_cap_cachep, GFP_NOFS);
+		if (!cap) {
+			spin_lock(&mdsc->caps_list_lock);
+			if (mdsc->caps_avail_count) {
+				BUG_ON(list_empty(&mdsc->caps_list));
+
+				mdsc->caps_avail_count--;
+				mdsc->caps_use_count++;
+				cap = list_first_entry(&mdsc->caps_list,
+						struct ceph_cap, caps_item);
+				list_del(&cap->caps_item);
+
+				BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
+				       mdsc->caps_reserve_count + mdsc->caps_avail_count);
+			}
+			spin_unlock(&mdsc->caps_list_lock);
+		}
+
 		if (cap) {
 			spin_lock(&mdsc->caps_list_lock);
 			mdsc->caps_use_count++;
-- 
1.8.3.1

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