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-rw-r--r--fs/nfsd/nfscache.c31
1 files changed, 27 insertions, 4 deletions
diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index fd81ca79a002..17cb0d6b9944 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -41,6 +41,12 @@ static unsigned int payload_misses;
/* amount of memory (in bytes) currently consumed by the DRC */
static unsigned int drc_mem_usage;
+/* longest hash chain seen */
+static unsigned int longest_chain;
+
+/* size of cache when we saw the longest hash chain */
+static unsigned int longest_chain_cachesize;
+
/*
* Calculate the hash index from an XID.
*/
@@ -319,15 +325,30 @@ nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
static struct svc_cacherep *
nfsd_cache_search(struct svc_rqst *rqstp, __wsum csum)
{
- struct svc_cacherep *rp;
+ struct svc_cacherep *rp, *ret = NULL;
struct hlist_head *rh;
+ unsigned int entries = 0;
rh = &cache_hash[request_hash(rqstp->rq_xid)];
hlist_for_each_entry(rp, rh, c_hash) {
- if (nfsd_cache_match(rqstp, csum, rp))
- return rp;
+ ++entries;
+ if (nfsd_cache_match(rqstp, csum, rp)) {
+ ret = rp;
+ break;
+ }
+ }
+
+ /* tally hash chain length stats */
+ if (entries > longest_chain) {
+ longest_chain = entries;
+ longest_chain_cachesize = num_drc_entries;
+ } else if (entries == longest_chain) {
+ /* prefer to keep the smallest cachesize possible here */
+ longest_chain_cachesize = min(longest_chain_cachesize,
+ num_drc_entries);
}
- return NULL;
+
+ return ret;
}
/*
@@ -573,6 +594,8 @@ static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v)
seq_printf(m, "cache misses: %u\n", nfsdstats.rcmisses);
seq_printf(m, "not cached: %u\n", nfsdstats.rcnocache);
seq_printf(m, "payload misses: %u\n", payload_misses);
+ seq_printf(m, "longest chain len: %u\n", longest_chain);
+ seq_printf(m, "cachesize at longest: %u\n", longest_chain_cachesize);
spin_unlock(&cache_lock);
return 0;
}