[PATCH v2 05/11] fs: add percpu counters to count fine vs. coarse timestamps

Jeff Layton
2024-07-01T10:27:19Z

Keep a pair of percpu counters so we can track what proportion of
timestamps is fine-grained.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
fs/inode.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)

diff --git a/fs/inode.c b/fs/inode.c
index 12790a26102c..5b5a1a8c0bb7 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>
@@ -64,6 +66,10 @@ static __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_hash_lock);

/* Don't send out a ctime lower than this (modulo backward clock jumps). */
static __cacheline_aligned_in_smp ktime_t ctime_floor;
+
+static struct percpu_counter mg_fine_ts;
+static struct percpu_counter mg_coarse_ts;
+
/*
* Empty aops. Can be used for the cases where the user does not
* define any of the address_space operations.
@@ -2636,6 +2642,9 @@ struct timespec64 inode_set_ctime_current(struct inode *inode)
trace_ctime_floor_update(inode, floor, now, old);
if (old != floor)
now = old;
+ percpu_counter_inc(&mg_fine_ts);
+ } else {
+ percpu_counter_inc(&mg_coarse_ts);
}
retry:
/* Try to swap the ctime into place. */
@@ -2711,3 +2720,32 @@ 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 fine = percpu_counter_sum(&mg_fine_ts);
+ u64 coarse = percpu_counter_sum(&mg_coarse_ts);
+
+ seq_printf(s, "%llu %llu\n", fine, coarse);
+ return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(mgts);
+
+static int __init mg_debugfs_init(void)
+{
+ int ret = percpu_counter_init(&mg_fine_ts, 0, GFP_KERNEL);
+
+ if (ret)
+ return ret;
+
+ ret = percpu_counter_init(&mg_coarse_ts, 0, GFP_KERNEL);
+ if (ret) {
+ percpu_counter_destroy(&mg_fine_ts);
+ 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