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Subject: [PATCH 36/67] fscache: Add stats for the cookie commit LRU
From:   David Howells <dhowells@redhat.com>
To:     linux-cachefs@redhat.com
Cc:     dhowells@redhat.com, Trond Myklebust <trondmy@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Steve French <sfrench@samba.org>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Jeff Layton <jlayton@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Omar Sandoval <osandov@osandov.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
        linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
        v9fs-developer@lists.sourceforge.net,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Mon, 18 Oct 2021 16:00:07 +0100
Message-ID: <163456920740.2614702.10833323576114946075.stgit@warthog.procyon.org.uk>
In-Reply-To: <163456861570.2614702.14754548462706508617.stgit@warthog.procyon.org.uk>
References: <163456861570.2614702.14754548462706508617.stgit@warthog.procyon.org.uk>
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Precedence: bulk

Add some stats to indicate the state of the cookie commit LRU, including an
indication of how many are currently on it, how many have been expired,
removed (withdrawn/reused) or dropped (relinquished) from it and how long
till the next reap happens.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/fscache/cookie.c   |   10 +++++++++-
 fs/fscache/internal.h |    5 +++++
 fs/fscache/stats.c    |   12 ++++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index dfc61b2e105d..c6b553609f33 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -28,7 +28,7 @@ static LIST_HEAD(fscache_cookies);
 static DEFINE_RWLOCK(fscache_cookies_lock);
 static LIST_HEAD(fscache_cookie_lru);
 static DEFINE_SPINLOCK(fscache_cookie_lru_lock);
-static DEFINE_TIMER(fscache_cookie_lru_timer, fscache_cookie_lru_timed_out);
+DEFINE_TIMER(fscache_cookie_lru_timer, fscache_cookie_lru_timed_out);
 static DECLARE_WORK(fscache_cookie_lru_work, fscache_cookie_lru_worker);
 static const char fscache_cookie_stages[FSCACHE_COOKIE_STAGE__NR] = "-LCAIFMWRD";
 unsigned int fscache_lru_cookie_timeout = 10 * HZ;
@@ -60,6 +60,8 @@ static void fscache_free_cookie(struct fscache_cookie *cookie)
 		spin_lock(&fscache_cookie_lru_lock);
 		list_del_init(&cookie->commit_link);
 		spin_unlock(&fscache_cookie_lru_lock);
+		fscache_stat_d(&fscache_n_cookies_lru);
+		fscache_stat(&fscache_n_cookies_lru_removed);
 	}
 	write_lock(&fscache_cookies_lock);
 	list_del(&cookie->proc_link);
@@ -525,6 +527,7 @@ void __fscache_unuse_cookie(struct fscache_cookie *cookie,
 			if (list_empty(&cookie->commit_link)) {
 				fscache_get_cookie(cookie, fscache_cookie_get_lru);
 				list_move_tail(&cookie->commit_link, &fscache_cookie_lru);
+				fscache_stat(&fscache_n_cookies_lru);
 			}
 			spin_unlock(&fscache_cookie_lru_lock);
 			timer_reduce(&fscache_cookie_lru_timer,
@@ -624,10 +627,12 @@ static void fscache_cookie_lru_do_one(struct fscache_cookie *cookie)
 	    time_before(jiffies, cookie->unused_at + fscache_lru_cookie_timeout) ||
 	    atomic_read(&cookie->n_active) > 0) {
 		spin_unlock(&cookie->lock);
+		fscache_stat(&fscache_n_cookies_lru_removed);
 	} else {
 		__fscache_set_cookie_stage(cookie, FSCACHE_COOKIE_STAGE_COMMITTING);
 		set_bit(FSCACHE_COOKIE_DO_COMMIT, &cookie->flags);
 		spin_unlock(&cookie->lock);
+		fscache_stat(&fscache_n_cookies_lru_expired);
 		_debug("lru c=%x", cookie->debug_id);
 		__fscache_withdraw_cookie(cookie);
 	}
@@ -652,6 +657,7 @@ static void fscache_cookie_lru_worker(struct work_struct *work)
 		}
 
 		list_del_init(&cookie->commit_link);
+		fscache_stat_d(&fscache_n_cookies_lru);
 		spin_unlock(&fscache_cookie_lru_lock);
 		fscache_cookie_lru_do_one(cookie);
 		spin_lock(&fscache_cookie_lru_lock);
@@ -673,6 +679,8 @@ static void fscache_cookie_drop_from_lru(struct fscache_cookie *cookie)
 		spin_lock(&fscache_cookie_lru_lock);
 		if (!list_empty(&cookie->commit_link)) {
 			list_del_init(&cookie->commit_link);
+			fscache_stat_d(&fscache_n_cookies_lru);
+			fscache_stat(&fscache_n_cookies_lru_dropped);
 			need_put = true;
 		}
 		spin_unlock(&fscache_cookie_lru_lock);
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index f74f7bdea633..62e6a5bbef8e 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -32,6 +32,7 @@ struct fscache_cache *fscache_lookup_cache(const char *name, bool is_cache);
  */
 extern struct kmem_cache *fscache_cookie_jar;
 extern const struct seq_operations fscache_cookies_seq_ops;
+extern struct timer_list fscache_cookie_lru_timer;
 
 extern void fscache_print_cookie(struct fscache_cookie *cookie, char prefix);
 extern bool fscache_begin_cookie_access(struct fscache_cookie *cookie,
@@ -70,6 +71,10 @@ extern atomic_t fscache_n_volumes;
 extern atomic_t fscache_n_volumes_collision;
 extern atomic_t fscache_n_volumes_nomem;
 extern atomic_t fscache_n_cookies;
+extern atomic_t fscache_n_cookies_lru;
+extern atomic_t fscache_n_cookies_lru_expired;
+extern atomic_t fscache_n_cookies_lru_removed;
+extern atomic_t fscache_n_cookies_lru_dropped;
 
 extern atomic_t fscache_n_retrievals;
 extern atomic_t fscache_n_retrievals_ok;
diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index 13e90b940bd2..5700e5712018 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -18,6 +18,10 @@ atomic_t fscache_n_volumes;
 atomic_t fscache_n_volumes_collision;
 atomic_t fscache_n_volumes_nomem;
 atomic_t fscache_n_cookies;
+atomic_t fscache_n_cookies_lru;
+atomic_t fscache_n_cookies_lru_expired;
+atomic_t fscache_n_cookies_lru_removed;
+atomic_t fscache_n_cookies_lru_dropped;
 
 atomic_t fscache_n_retrievals;
 atomic_t fscache_n_retrievals_ok;
@@ -89,6 +93,14 @@ int fscache_stats_show(struct seq_file *m, void *v)
 		   atomic_read(&fscache_n_acquires_nobufs),
 		   atomic_read(&fscache_n_acquires_oom));
 
+	seq_printf(m, "LRU    : n=%u exp=%u rmv=%u drp=%u at=%ld\n",
+		   atomic_read(&fscache_n_cookies_lru),
+		   atomic_read(&fscache_n_cookies_lru_expired),
+		   atomic_read(&fscache_n_cookies_lru_removed),
+		   atomic_read(&fscache_n_cookies_lru_dropped),
+		   timer_pending(&fscache_cookie_lru_timer) ?
+		   fscache_cookie_lru_timer.expires - jiffies : 0);
+
 	seq_printf(m, "Invals : n=%u run=%u\n",
 		   atomic_read(&fscache_n_invalidates),
 		   atomic_read(&fscache_n_invalidates_run));