Keep a pair of percpu counters so we can track what proportion of timestamps is fine-grained.
Signed-off-by: Jeff Layton <[email protected]> --- 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