linux-kernel - [PATCH 03/10] staging: lustre: lu_object: discard extra lru count.

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Message-ID: <152565448808.30131.17399451482748227169.stgit@noble>
Date:   Mon, 07 May 2018 10:54:48 +1000
From:   NeilBrown <neilb@...e.com>
To:     Oleg Drokin <oleg.drokin@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        James Simmons <jsimmons@...radead.org>,
        Andreas Dilger <andreas.dilger@...el.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lustre Development List <lustre-devel@...ts.lustre.org>
Subject: [PATCH 03/10] staging: lustre: lu_object: discard extra lru count.

lu_object maintains 2 lru counts.
One is a per-bucket lsb_lru_len.
The other is the per-cpu ls_lru_len_counter.

The only times the per-bucket counters are use are:
- a debug message when an object is added
- in lu_site_stats_get when all the counters are combined.

The debug message is not essential, and the per-cpu counter
can be used to get the combined total.

So discard the per-bucket lsb_lru_len.

Reviewed-by: Andreas Dilger <andreas.dilger@...ger.ca>
Signed-off-by: NeilBrown <neilb@...e.com>
---
 drivers/staging/lustre/lustre/obdclass/lu_object.c |   27 +++++++++-----------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/drivers/staging/lustre/lustre/obdclass/lu_object.c b/drivers/staging/lustre/lustre/obdclass/lu_object.c
index 83dacc413c32..bf5b309edeae 100644
--- a/drivers/staging/lustre/lustre/obdclass/lu_object.c
+++ b/drivers/staging/lustre/lustre/obdclass/lu_object.c
@@ -57,10 +57,6 @@
 #include <linux/list.h>
 
 struct lu_site_bkt_data {
-	/**
-	 * number of object in this bucket on the lsb_lru list.
-	 */
-	long			lsb_lru_len;
 	/**
 	 * LRU list, updated on each access to object. Protected by
 	 * bucket lock of lu_site::ls_obj_hash.
@@ -188,10 +184,9 @@ void lu_object_put(const struct lu_env *env, struct lu_object *o)
 	if (!lu_object_is_dying(top)) {
 		LASSERT(list_empty(&top->loh_lru));
 		list_add_tail(&top->loh_lru, &bkt->lsb_lru);
-		bkt->lsb_lru_len++;
 		percpu_counter_inc(&site->ls_lru_len_counter);
-		CDEBUG(D_INODE, "Add %p to site lru. hash: %p, bkt: %p, lru_len: %ld\n",
-		       o, site->ls_obj_hash, bkt, bkt->lsb_lru_len);
+		CDEBUG(D_INODE, "Add %p to site lru. hash: %p, bkt: %p\n",
+		       o, site->ls_obj_hash, bkt);
 		cfs_hash_bd_unlock(site->ls_obj_hash, &bd, 1);
 		return;
 	}
@@ -239,7 +234,6 @@ void lu_object_unhash(const struct lu_env *env, struct lu_object *o)
 
 			list_del_init(&top->loh_lru);
 			bkt = cfs_hash_bd_extra_get(obj_hash, &bd);
-			bkt->lsb_lru_len--;
 			percpu_counter_dec(&site->ls_lru_len_counter);
 		}
 		cfs_hash_bd_del_locked(obj_hash, &bd, &top->loh_hash);
@@ -423,7 +417,6 @@ int lu_site_purge_objects(const struct lu_env *env, struct lu_site *s,
 			cfs_hash_bd_del_locked(s->ls_obj_hash,
 					       &bd2, &h->loh_hash);
 			list_move(&h->loh_lru, &dispose);
-			bkt->lsb_lru_len--;
 			percpu_counter_dec(&s->ls_lru_len_counter);
 			if (did_sth == 0)
 				did_sth = 1;
@@ -622,7 +615,6 @@ static struct lu_object *htable_lookup(struct lu_site *s,
 		lprocfs_counter_incr(s->ls_stats, LU_SS_CACHE_HIT);
 		if (!list_empty(&h->loh_lru)) {
 			list_del_init(&h->loh_lru);
-			bkt->lsb_lru_len--;
 			percpu_counter_dec(&s->ls_lru_len_counter);
 		}
 		return lu_object_top(h);
@@ -1835,19 +1827,24 @@ struct lu_site_stats {
 	unsigned int	lss_busy;
 };
 
-static void lu_site_stats_get(struct cfs_hash *hs,
+static void lu_site_stats_get(const struct lu_site *s,
 			      struct lu_site_stats *stats, int populated)
 {
+	struct cfs_hash *hs = s->ls_obj_hash;
 	struct cfs_hash_bd bd;
 	unsigned int i;
+	/*
+	 * percpu_counter_sum_positive() won't accept a const pointer
+	 * as it does modify the struct by taking a spinlock
+	 */
+	struct lu_site *s2 = (struct lu_site *)s;
 
+	stats->lss_busy += cfs_hash_size_get(hs) -
+		percpu_counter_sum_positive(&s2->ls_lru_len_counter);
 	cfs_hash_for_each_bucket(hs, &bd, i) {
-		struct lu_site_bkt_data *bkt = cfs_hash_bd_extra_get(hs, &bd);
 		struct hlist_head	*hhead;
 
 		cfs_hash_bd_lock(hs, &bd, 1);
-		stats->lss_busy  +=
-			cfs_hash_bd_count_get(&bd) - bkt->lsb_lru_len;
 		stats->lss_total += cfs_hash_bd_count_get(&bd);
 		stats->lss_max_search = max((int)stats->lss_max_search,
 					    cfs_hash_bd_depmax_get(&bd));
@@ -2040,7 +2037,7 @@ int lu_site_stats_print(const struct lu_site *s, struct seq_file *m)
 	struct lu_site_stats stats;
 
 	memset(&stats, 0, sizeof(stats));
-	lu_site_stats_get(s->ls_obj_hash, &stats, 1);
+	lu_site_stats_get(s, &stats, 1);
 
 	seq_printf(m, "%d/%d %d/%ld %d %d %d %d %d %d %d\n",
 		   stats.lss_busy,