[PATCH 36/67] fscache: Add stats for the cookie commit LRU

David Howells
2021-10-18T15:00:25Z

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removed (withdrawn/reused) or dropped (relinquished) from it and how long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));