This is a note to let you know that I've just added the patch titled
NFSD: Report average age of filecache items
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nfsd-report-average-age-of-filecache-items.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9f8bda64df8ab4477cdd526ac2b344868678168e
Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
Date: Fri Jul 8 14:24:12 2022 -0400
NFSD: Report average age of filecache items
[ Upstream commit 904940e94a887701db24401e3ed6928a1d4e329f ]
This is a measure of how long items stay in the filecache, to help
assess how efficient the cache is.
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 5d31622c23040..0cd72c20fc12d 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -44,6 +44,7 @@ struct nfsd_fcache_bucket {
static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits);
static DEFINE_PER_CPU(unsigned long, nfsd_file_acquisitions);
static DEFINE_PER_CPU(unsigned long, nfsd_file_releases);
+static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age);
struct nfsd_fcache_disposal {
struct work_struct work;
@@ -177,6 +178,7 @@ nfsd_file_alloc(struct inode *inode, unsigned int may, unsigned int hashval,
if (nf) {
INIT_HLIST_NODE(&nf->nf_node);
INIT_LIST_HEAD(&nf->nf_lru);
+ nf->nf_birthtime = ktime_get();
nf->nf_file = NULL;
nf->nf_cred = get_current_cred();
nf->nf_net = net;
@@ -194,9 +196,11 @@ nfsd_file_alloc(struct inode *inode, unsigned int may, unsigned int hashval,
static bool
nfsd_file_free(struct nfsd_file *nf)
{
+ s64 age = ktime_to_ms(ktime_sub(ktime_get(), nf->nf_birthtime));
bool flush = false;
this_cpu_inc(nfsd_file_releases);
+ this_cpu_add(nfsd_file_total_age, age);
trace_nfsd_file_put_final(nf);
if (nf->nf_mark)
@@ -1054,7 +1058,7 @@ static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
{
unsigned long hits = 0, acquisitions = 0, releases = 0;
unsigned int i, count = 0, longest = 0;
- unsigned long lru = 0;
+ unsigned long lru = 0, total_age = 0;
/*
* No need for spinlocks here since we're not terribly interested in
@@ -1075,6 +1079,7 @@ static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
hits += per_cpu(nfsd_file_cache_hits, i);
acquisitions += per_cpu(nfsd_file_acquisitions, i);
releases += per_cpu(nfsd_file_releases, i);
+ total_age += per_cpu(nfsd_file_total_age, i);
}
seq_printf(m, "total entries: %u\n", count);
@@ -1083,6 +1088,10 @@ static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
seq_printf(m, "cache hits: %lu\n", hits);
seq_printf(m, "acquisitions: %lu\n", acquisitions);
seq_printf(m, "releases: %lu\n", releases);
+ if (releases)
+ seq_printf(m, "mean age (ms): %ld\n", total_age / releases);
+ else
+ seq_printf(m, "mean age (ms): -\n");
return 0;
}
diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
index c9e3c6eb4776e..c6ad5fe47f12f 100644
--- a/fs/nfsd/filecache.h
+++ b/fs/nfsd/filecache.h
@@ -44,6 +44,7 @@ struct nfsd_file {
refcount_t nf_ref;
unsigned char nf_may;
struct nfsd_file_mark *nf_mark;
+ ktime_t nf_birthtime;
};
int nfsd_file_cache_init(void);
