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Subject: [PATCH RFC 02/30] NFSD: Report count of calls to nfsd_file_acquire()
From:   Chuck Lever <chuck.lever@oracle.com>
To:     linux-nfs@vger.kernel.org, netdev@vger.kernel.org
Cc:     david@fromorbit.com, tgraf@suug.ch, jlayton@redhat.com
Date:   Wed, 22 Jun 2022 10:12:59 -0400
Message-ID: <165590717916.75778.4135678773284445735.stgit@manet.1015granger.net>
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References: <165590626293.75778.9843437418112335153.stgit@manet.1015granger.net>
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Count the number of successful acquisitions that did not create a
file (ie, acquisitions that do not result in a compulsory cache
miss). This count can be compared directly with the reported hit
count to compute a hit ratio.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/filecache.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 932db96f854a..128e8934f12a 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -43,6 +43,7 @@ struct nfsd_fcache_bucket {
 };
 
 static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits);
+static DEFINE_PER_CPU(unsigned long, nfsd_file_acquisitions);
 
 struct nfsd_fcache_disposal {
 	struct work_struct work;
@@ -975,6 +976,8 @@ nfsd_do_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	}
 out:
 	if (status == nfs_ok) {
+		if (open)
+			this_cpu_inc(nfsd_file_acquisitions);
 		*pnf = nf;
 	} else {
 		nfsd_file_put(nf);
@@ -1067,8 +1070,8 @@ nfsd_file_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
  */
 static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
 {
+	unsigned long hits = 0, acquisitions = 0;
 	unsigned int i, count = 0, longest = 0;
-	unsigned long hits = 0;
 
 	/*
 	 * No need for spinlocks here since we're not terribly interested in
@@ -1084,13 +1087,16 @@ static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
 	}
 	mutex_unlock(&nfsd_mutex);
 
-	for_each_possible_cpu(i)
+	for_each_possible_cpu(i) {
 		hits += per_cpu(nfsd_file_cache_hits, i);
+		acquisitions += per_cpu(nfsd_file_acquisitions, i);
+	}
 
 	seq_printf(m, "total entries: %u\n", count);
 	seq_printf(m, "longest chain: %u\n", longest);
 	seq_printf(m, "lru entries:   %lu\n", list_lru_count(&nfsd_file_lru));
 	seq_printf(m, "cache hits:    %lu\n", hits);
+	seq_printf(m, "acquisitions:  %lu\n", acquisitions);
 	return 0;
 }