Keep a pair of percpu counters so we can track what proportion of
timestamps is fine-grained.
Signed-off-by: Jeff Layton <jlay...@kernel.org>
---
fs/inode.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 48 insertions(+), 1 deletion(-)
diff --git a/fs/inode.c b/fs/inode.c
index 4ab7aee3558c..2e5610ebb205 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -21,6 +21,8 @@
#include <linux/list_lru.h>
#include <linux/iversion.h>
#include <linux/rw_hint.h>
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
#include <trace/events/writeback.h>
#define CREATE_TRACE_POINTS
#include <trace/events/timestamp.h>
@@ -69,6 +71,11 @@ static __cacheline_aligned_in_smp
DEFINE_SPINLOCK(inode_hash_lock);
* converted to the realtime clock on an as-needed basis.
*/
static __cacheline_aligned_in_smp ktime_t ctime_floor;
+
+static struct percpu_counter mg_ctime_updates;
+static struct percpu_counter mg_floor_swaps;
+static struct percpu_counter mg_ctime_swaps;
+
/*
* Empty aops. Can be used for the cases where the user does not
* define any of the address_space operations.
@@ -2662,11 +2669,14 @@ struct timespec64 inode_set_ctime_current(struct inode
*inode)
* as good, so keep it.
*/
old = cmpxchg(&ctime_floor, floor, fine);
- if (old != floor)
+ if (old == floor)
+ percpu_counter_inc(&mg_floor_swaps);
+ else
fine = old;
now = ktime_mono_to_real(fine);
}
}
+ percpu_counter_inc(&mg_ctime_updates);
now_ts = ktime_to_timespec64(now);
retry:
/* Try to swap the nsec value into place. */
@@ -2676,6 +2686,7 @@ struct timespec64 inode_set_ctime_current(struct inode
*inode)
/* If swap occurred, then we're (mostly) done */
if (cur == cns) {
inode->i_ctime_sec = now_ts.tv_sec;
+ percpu_counter_inc(&mg_ctime_swaps);
} else {
/*
* Was the change due to someone marking the old ctime QUERIED?
@@ -2745,3 +2756,39 @@ umode_t mode_strip_sgid(struct mnt_idmap *idmap,
return mode & ~S_ISGID;
}
EXPORT_SYMBOL(mode_strip_sgid);
+
+static int mgts_show(struct seq_file *s, void *p)
+{
+ u64 ctime_updates = percpu_counter_sum(&mg_ctime_updates);
+ u64 floor_swaps = percpu_counter_sum(&mg_floor_swaps);
+ u64 ctime_swaps = percpu_counter_sum(&mg_ctime_swaps);
+
+ seq_printf(s, "%llu %llu %llu\n", ctime_updates, ctime_swaps,
floor_swaps);
+ return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(mgts);
+
+static int __init mg_debugfs_init(void)
+{
+ int ret = percpu_counter_init(&mg_ctime_updates, 0, GFP_KERNEL);
+
+ if (ret)
+ return ret;
+
+ ret = percpu_counter_init(&mg_floor_swaps, 0, GFP_KERNEL);
+ if (ret) {
+ percpu_counter_destroy(&mg_ctime_updates);
+ return ret;
+ }
+
+ ret = percpu_counter_init(&mg_ctime_swaps, 0, GFP_KERNEL);
+ if (ret) {
+ percpu_counter_destroy(&mg_floor_swaps);
+ percpu_counter_destroy(&mg_ctime_updates);
+ return ret;
+ }
+ debugfs_create_file("multigrain_timestamps", S_IFREG | S_IRUGO, NULL,
NULL, &mgts_fops);
+ return 0;
+}
+late_initcall(mg_debugfs_init);
--
2.45.2
