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Message-Id: <20240711-mgtime-v5-3-37bb5b465feb@kernel.org>
Date: Thu, 11 Jul 2024 07:08:07 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Chandan Babu R <chandan.babu@...cle.com>,
"Darrick J. Wong" <djwong@...nel.org>, Theodore Ts'o <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>, Chris Mason <clm@...com>,
Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>,
Hugh Dickins <hughd@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>,
Jonathan Corbet <corbet@....net>
Cc: Dave Chinner <david@...morbit.com>, Andi Kleen <ak@...ux.intel.com>,
Christoph Hellwig <hch@...radead.org>, Uros Bizjak <ubizjak@...il.com>,
Kent Overstreet <kent.overstreet@...ux.dev>, Arnd Bergmann <arnd@...db.de>,
Randy Dunlap <rdunlap@...radead.org>, kernel-team@...com,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
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Jeff Layton <jlayton@...nel.org>
Subject: [PATCH v5 3/9] fs: add percpu counters for significant multigrain
timestamp events
Four percpu counters for counting various stats around mgtimes, and a
new debugfs file for displaying them:
- number of attempted ctime updates
- number of successful i_ctime_nsec swaps
- number of fine-grained timestamp fetches
- number of floor value swaps
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
fs/inode.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 59 insertions(+), 1 deletion(-)
diff --git a/fs/inode.c b/fs/inode.c
index 81b45e0a95a6..011148c82901 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>
@@ -70,6 +72,11 @@ static __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_hash_lock);
*/
static __cacheline_aligned_in_smp atomic64_t ctime_floor;
+static struct percpu_counter mg_ctime_updates;
+static struct percpu_counter mg_floor_swaps;
+static struct percpu_counter mg_ctime_swaps;
+static struct percpu_counter mg_fine_stamps;
+
/*
* Empty aops. Can be used for the cases where the user does not
* define any of the address_space operations.
@@ -2654,6 +2661,7 @@ struct timespec64 inode_set_ctime_current(struct inode *inode)
/* Get a fine-grained time */
fine = ktime_get();
+ percpu_counter_inc(&mg_fine_stamps);
/*
* If the cmpxchg works, we take the new floor value. If
@@ -2662,11 +2670,14 @@ struct timespec64 inode_set_ctime_current(struct inode *inode)
* as good, so keep it.
*/
old = floor;
- if (!atomic64_try_cmpxchg(&ctime_floor, &old, fine))
+ if (atomic64_try_cmpxchg(&ctime_floor, &old, fine))
+ percpu_counter_inc(&mg_floor_swaps);
+ else
fine = old;
now = ktime_mono_to_real(fine);
}
}
+ percpu_counter_inc(&mg_ctime_updates);
now_ts = timestamp_truncate(ktime_to_timespec64(now), inode);
cur = cns;
retry:
@@ -2675,6 +2686,7 @@ struct timespec64 inode_set_ctime_current(struct inode *inode)
/* If swap occurred, then we're (mostly) done */
inode->i_ctime_sec = now_ts.tv_sec;
trace_ctime_ns_xchg(inode, cns, now_ts.tv_nsec, cur);
+ percpu_counter_inc(&mg_ctime_swaps);
} else {
/*
* Was the change due to someone marking the old ctime QUERIED?
@@ -2744,3 +2756,49 @@ 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 ctime_swaps = percpu_counter_sum(&mg_ctime_swaps);
+ u64 fine_stamps = percpu_counter_sum(&mg_fine_stamps);
+ u64 floor_swaps = percpu_counter_sum(&mg_floor_swaps);
+
+ seq_printf(s, "%llu %llu %llu %llu\n",
+ ctime_updates, ctime_swaps, fine_stamps, 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;
+ }
+
+ ret = percpu_counter_init(&mg_fine_stamps, 0, GFP_KERNEL);
+ if (ret) {
+ percpu_counter_destroy(&mg_floor_swaps);
+ percpu_counter_destroy(&mg_ctime_updates);
+ percpu_counter_destroy(&mg_ctime_swaps);
+ 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
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