Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-qc0-f170.google.com ([209.85.216.170]:55717 "EHLO mail-qc0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756211Ab3BUS2u (ORCPT ); Thu, 21 Feb 2013 13:28:50 -0500 Received: by mail-qc0-f170.google.com with SMTP id d42so3762883qca.15 for ; Thu, 21 Feb 2013 10:28:49 -0800 (PST) From: Jeff Layton To: bfields@fieldses.org Cc: linux-nfs@vger.kernel.org Subject: [PATCH v2 5/5] nfsd: keep track of the max and average time to search the cache Date: Thu, 21 Feb 2013 13:28:38 -0500 Message-Id: <1361471318-17971-6-git-send-email-jlayton@redhat.com> In-Reply-To: <1361471318-17971-1-git-send-email-jlayton@redhat.com> References: <1361471318-17971-1-git-send-email-jlayton@redhat.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Since we're moderately concerned about the potential increase in hash chain lengths, keep a running average of the time and the max time to search. Signed-off-by: Jeff Layton --- fs/nfsd/nfscache.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c index 52493cb..ae6575d 100644 --- a/fs/nfsd/nfscache.c +++ b/fs/nfsd/nfscache.c @@ -33,6 +33,9 @@ static unsigned int max_drc_entries; /* max number of entries */ static unsigned int drc_mem_usage; /* memory used by cache */ static unsigned int csum_misses; /* cache misses due only to csum comparison failures */ +static unsigned int max_search_time; /* max time to search */ +static unsigned int avg_search_time; /* avg time to search */ + /* * Calculate the hash index from an XID. */ @@ -310,16 +313,28 @@ 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_node *hn; struct hlist_head *rh; + ktime_t start; + unsigned int delta; + static unsigned int nsearches = 0; + unsigned int osearches; + start = ktime_get(); rh = &cache_hash[request_hash(rqstp->rq_xid)]; hlist_for_each_entry(rp, hn, rh, c_hash) { - if (nfsd_cache_match(rqstp, csum, rp)) - return rp; + if (nfsd_cache_match(rqstp, csum, rp)) { + ret = rp; + break; + } } - return NULL; + delta = (unsigned int)ktime_to_ns(ktime_sub(ktime_get(), start)); + osearches = nsearches++; + avg_search_time = (avg_search_time * osearches + delta) / nsearches; + max_search_time = max(max_search_time, delta); + + return ret; } /* @@ -589,6 +604,8 @@ static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v) seq_printf(m, "not cached: %u\n", nfsdstats.rcnocache); seq_printf(m, "checksum misses: %u\n", csum_misses); seq_printf(m, "max chain len: %u\n", nfsd_repcache_max_chain_len()); + seq_printf(m, "avg search time: %uns\n", avg_search_time); + seq_printf(m, "max search time: %uns\n", max_search_time); spin_unlock(&cache_lock); return 0; } -- 1.7.11.7