ocfs2: Use hrtimer to track ocfs2 fs lock stats

Patch makes use of the hrtimer to track times in ocfs2 lock stats.

The patch is a bit involved to ensure no additional impact on the memory
footprint. The size of ocfs2_inode_cache remains 1280 bytes on 32-bit systems.

A related change was to modify the unit of the max wait time from nanosec to
microsec allowing us to track max time larger than 4 secs. This change
necessitated the bumping of the output version in the debugfs file,
locking_state, from 2 to 3.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Joel Becker <jlbec@evilplan.org>

2 files changed, 64 insertions, 56 deletions

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index e8d94d722ec..7484bb9a343 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -64,7 +64,7 @@ struct ocfs2_mask_waiter {
         unsigned long           mw_mask;
         unsigned long           mw_goal;
 #ifdef CONFIG_OCFS2_FS_STATS
-        unsigned long long      mw_lock_start;
+        ktime_t                 mw_lock_start;
 #endif
 };
 
@@ -435,44 +435,41 @@ static void ocfs2_remove_lockres_tracking(struct ocfs2_lock_res *res)
 #ifdef CONFIG_OCFS2_FS_STATS
 static void ocfs2_init_lock_stats(struct ocfs2_lock_res *res)
 {
-        res->l_lock_num_prmode = 0;
-        res->l_lock_num_prmode_failed = 0;
-        res->l_lock_total_prmode = 0;
-        res->l_lock_max_prmode = 0;
-        res->l_lock_num_exmode = 0;
-        res->l_lock_num_exmode_failed = 0;
-        res->l_lock_total_exmode = 0;
-        res->l_lock_max_exmode = 0;
         res->l_lock_refresh = 0;
+        memset(&res->l_lock_prmode, 0, sizeof(struct ocfs2_lock_stats));
+        memset(&res->l_lock_exmode, 0, sizeof(struct ocfs2_lock_stats));
 }
 
 static void ocfs2_update_lock_stats(struct ocfs2_lock_res *res, int level,
                                     struct ocfs2_mask_waiter *mw, int ret)
 {
-        unsigned long long *num, *sum;
-        unsigned int *max, *failed;
-        struct timespec ts = current_kernel_time();
-        unsigned long long time = timespec_to_ns(&ts) - mw->mw_lock_start;
-
-        if (level == LKM_PRMODE) {
-                num = &res->l_lock_num_prmode;
-                sum = &res->l_lock_total_prmode;
-                max = &res->l_lock_max_prmode;
-                failed = &res->l_lock_num_prmode_failed;
-        } else if (level == LKM_EXMODE) {
-                num = &res->l_lock_num_exmode;
-                sum = &res->l_lock_total_exmode;
-                max = &res->l_lock_max_exmode;
-                failed = &res->l_lock_num_exmode_failed;
-        } else
+        u32 usec;
+        ktime_t kt;
+        struct ocfs2_lock_stats *stats;
+
+        if (level == LKM_PRMODE)
+                stats = &res->l_lock_prmode;
+        else if (level == LKM_EXMODE)
+                stats = &res->l_lock_exmode;
+        else
                 return;
 
-        (*num)++;
-        (*sum) += time;
-        if (time > *max)
-                *max = time;
+        kt = ktime_sub(ktime_get(), mw->mw_lock_start);
+        usec = ktime_to_us(kt);
+
+        stats->ls_gets++;
+        stats->ls_total += ktime_to_ns(kt);
+        /* overflow */
+        if (unlikely(stats->ls_gets) == 0) {
+                stats->ls_gets++;
+                stats->ls_total = ktime_to_ns(kt);
+        }
+
+        if (stats->ls_max < usec)
+                stats->ls_max = usec;
+
         if (ret)
-                (*failed)++;
+                stats->ls_fail++;
 }
 
 static inline void ocfs2_track_lock_refresh(struct ocfs2_lock_res *lockres)
@@ -482,8 +479,7 @@ static inline void ocfs2_track_lock_refresh(struct ocfs2_lock_res *lockres)
 
 static inline void ocfs2_init_start_time(struct ocfs2_mask_waiter *mw)
 {
-        struct timespec ts = current_kernel_time();
-        mw->mw_lock_start = timespec_to_ns(&ts);
+        mw->mw_lock_start = ktime_get();
 }
 #else
 static inline void ocfs2_init_lock_stats(struct ocfs2_lock_res *res)
@@ -2869,8 +2865,15 @@ static void *ocfs2_dlm_seq_next(struct seq_file *m, void *v, loff_t *pos)
         return iter;
 }
 
-/* So that debugfs.ocfs2 can determine which format is being used */
-#define OCFS2_DLM_DEBUG_STR_VERSION 2
+/*
+ * Version is used by debugfs.ocfs2 to determine the format being used
+ *
+ * New in version 2
+ *      - Lock stats printed
+ * New in version 3
+ *      - Max time in lock stats is in usecs (instead of nsecs)
+ */
+#define OCFS2_DLM_DEBUG_STR_VERSION 3
 static int ocfs2_dlm_seq_show(struct seq_file *m, void *v)
 {
         int i;
@@ -2912,18 +2915,18 @@ static int ocfs2_dlm_seq_show(struct seq_file *m, void *v)
                 seq_printf(m, "0x%x\t", lvb[i]);
 
 #ifdef CONFIG_OCFS2_FS_STATS
-# define lock_num_prmode(_l)            (_l)->l_lock_num_prmode
-# define lock_num_exmode(_l)            (_l)->l_lock_num_exmode
-# define lock_num_prmode_failed(_l)     (_l)->l_lock_num_prmode_failed
-# define lock_num_exmode_failed(_l)     (_l)->l_lock_num_exmode_failed
-# define lock_total_prmode(_l)          (_l)->l_lock_total_prmode
-# define lock_total_exmode(_l)          (_l)->l_lock_total_exmode
-# define lock_max_prmode(_l)            (_l)->l_lock_max_prmode
-# define lock_max_exmode(_l)            (_l)->l_lock_max_exmode
-# define lock_refresh(_l)               (_l)->l_lock_refresh
+# define lock_num_prmode(_l)            ((_l)->l_lock_prmode.ls_gets)
+# define lock_num_exmode(_l)            ((_l)->l_lock_exmode.ls_gets)
+# define lock_num_prmode_failed(_l)     ((_l)->l_lock_prmode.ls_fail)
+# define lock_num_exmode_failed(_l)     ((_l)->l_lock_exmode.ls_fail)
+# define lock_total_prmode(_l)          ((_l)->l_lock_prmode.ls_total)
+# define lock_total_exmode(_l)          ((_l)->l_lock_exmode.ls_total)
+# define lock_max_prmode(_l)            ((_l)->l_lock_prmode.ls_max)
+# define lock_max_exmode(_l)            ((_l)->l_lock_exmode.ls_max)
+# define lock_refresh(_l)               ((_l)->l_lock_refresh)
 #else
-# define lock_num_prmode(_l)            (0ULL)
-# define lock_num_exmode(_l)            (0ULL)
+# define lock_num_prmode(_l)            (0)
+# define lock_num_exmode(_l)            (0)
 # define lock_num_prmode_failed(_l)     (0)
 # define lock_num_exmode_failed(_l)     (0)
 # define lock_total_prmode(_l)          (0ULL)
@@ -2933,8 +2936,8 @@ static int ocfs2_dlm_seq_show(struct seq_file *m, void *v)
 # define lock_refresh(_l)               (0)
 #endif
         /* The following seq_print was added in version 2 of this output */
-        seq_printf(m, "%llu\t"
-                   "%llu\t"
+        seq_printf(m, "%u\t"
+                   "%u\t"
                    "%u\t"
                    "%u\t"
                    "%llu\t"
diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index 51cd6898e7f..4e3d3c1363f 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -147,6 +147,17 @@ struct ocfs2_lock_res_ops;
 
 typedef void (*ocfs2_lock_callback)(int status, unsigned long data);
 
+#ifdef CONFIG_OCFS2_FS_STATS
+struct ocfs2_lock_stats {
+        u64             ls_total;       /* Total wait in NSEC */
+        u32             ls_gets;        /* Num acquires */
+        u32             ls_fail;        /* Num failed acquires */
+
+        /* Storing max wait in usecs saves 24 bytes per inode */
+        u32             ls_max;         /* Max wait in USEC */
+};
+#endif
+
 struct ocfs2_lock_res {
         void                    *l_priv;
         struct ocfs2_lock_res_ops *l_ops;
@@ -182,15 +193,9 @@ struct ocfs2_lock_res {
         struct list_head         l_debug_list;
 
 #ifdef CONFIG_OCFS2_FS_STATS
-        unsigned long long       l_lock_num_prmode;        /* PR acquires */
-        unsigned long long       l_lock_num_exmode;        /* EX acquires */
-        unsigned int             l_lock_num_prmode_failed; /* Failed PR gets */
-        unsigned int             l_lock_num_exmode_failed; /* Failed EX gets */
-        unsigned long long       l_lock_total_prmode;      /* Tot wait for PR */
-        unsigned long long       l_lock_total_exmode;      /* Tot wait for EX */
-        unsigned int             l_lock_max_prmode;        /* Max wait for PR */
-        unsigned int             l_lock_max_exmode;        /* Max wait for EX */
-        unsigned int             l_lock_refresh;           /* Disk refreshes */
+        struct ocfs2_lock_stats  l_lock_prmode;         /* PR mode stats */
+        u32                      l_lock_refresh;        /* Disk refreshes */
+        struct ocfs2_lock_stats  l_lock_exmode;         /* EX mode stats */
 #endif
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
         struct lockdep_map       l_lockdep_map;