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fs: add percpu counters for significant multigrain timestamp events

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New percpu counters for counting various stats around multigrain
timestamp events, and a new debugfs file for displaying them when
CONFIG_DEBUG_FS is enabled:

- number of attempted ctime updates
- number of successful i_ctime_nsec swaps
- number of fine-grained timestamp fetches
- number of floor value swap events

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # documentation bits
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20241002-mgtime-v10-7-d1c4717f5284@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Jeff Layton 2024-10-02 17:27:22 -04:00 committed by Christian Brauner
parent c86e3c4718
commit 73a47cf40f
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GPG Key ID: 91C61BC06578DCA2
1 changed files with 69 additions and 0 deletions
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69
fs/inode.c
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@ -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>
@ -101,6 +103,70 @@ long get_nr_dirty_inodes(void)
return nr_dirty > 0 ? nr_dirty : 0;
}
#ifdef CONFIG_DEBUG_FS
static DEFINE_PER_CPU(long, mg_ctime_updates);
static DEFINE_PER_CPU(long, mg_fine_stamps);
static DEFINE_PER_CPU(long, mg_ctime_swaps);
static unsigned long get_mg_ctime_updates(void)
{
unsigned long sum = 0;
int i;
for_each_possible_cpu(i)
sum += data_race(per_cpu(mg_ctime_updates, i));
return sum;
}
static unsigned long get_mg_fine_stamps(void)
{
unsigned long sum = 0;
int i;
for_each_possible_cpu(i)
sum += data_race(per_cpu(mg_fine_stamps, i));
return sum;
}
static unsigned long get_mg_ctime_swaps(void)
{
unsigned long sum = 0;
int i;
for_each_possible_cpu(i)
sum += data_race(per_cpu(mg_ctime_swaps, i));
return sum;
}
#define mgtime_counter_inc(__var) this_cpu_inc(__var)
static int mgts_show(struct seq_file *s, void *p)
{
unsigned long ctime_updates = get_mg_ctime_updates();
unsigned long ctime_swaps = get_mg_ctime_swaps();
unsigned long fine_stamps = get_mg_fine_stamps();
unsigned long floor_swaps = timekeeping_get_mg_floor_swaps();
seq_printf(s, "%lu %lu %lu %lu\n",
ctime_updates, ctime_swaps, fine_stamps, floor_swaps);
return 0;
}
DEFINE_SHOW_ATTRIBUTE(mgts);
static int __init mg_debugfs_init(void)
{
debugfs_create_file("multigrain_timestamps", S_IFREG | S_IRUGO, NULL, NULL, &mgts_fops);
return 0;
}
late_initcall(mg_debugfs_init);
#else /* ! CONFIG_DEBUG_FS */
#define mgtime_counter_inc(__var) do { } while (0)
#endif /* CONFIG_DEBUG_FS */
/*
* Handle nr_inode sysctl
*/
@ -2689,8 +2755,10 @@ struct timespec64 inode_set_ctime_current(struct inode *inode)
if (timespec64_compare(&now, &ctime) <= 0) {
ktime_get_real_ts64_mg(&now);
now = timestamp_truncate(now, inode);
mgtime_counter_inc(mg_fine_stamps);
}
}
mgtime_counter_inc(mg_ctime_updates);
/* No need to cmpxchg if it's exactly the same */
if (cns == now.tv_nsec && inode->i_ctime_sec == now.tv_sec) {
@ -2704,6 +2772,7 @@ retry:
/* If swap occurred, then we're (mostly) done */
inode->i_ctime_sec = now.tv_sec;
trace_ctime_ns_xchg(inode, cns, now.tv_nsec, cur);
mgtime_counter_inc(mg_ctime_swaps);
} else {
/*
* Was the change due to someone marking the old ctime QUERIED?