On Mon 15-07-24 15:53:42, Jeff Layton wrote: > On Mon, 2024-07-15 at 11:32 -0700, Darrick J. Wong wrote: > > On Mon, Jul 15, 2024 at 08:48:54AM -0400, Jeff Layton wrote: > > > 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 > > > > > > Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx> > > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > > > --- > > > fs/inode.c | 70 > > > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- > > > 1 file changed, 69 insertions(+), 1 deletion(-) > > > > > > diff --git a/fs/inode.c b/fs/inode.c > > > index 869994285e87..fff844345c35 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> > > > @@ -80,6 +82,10 @@ EXPORT_SYMBOL(empty_aops); > > > > > > static DEFINE_PER_CPU(unsigned long, nr_inodes); > > > static DEFINE_PER_CPU(unsigned long, nr_unused); > > > +static DEFINE_PER_CPU(unsigned long, mg_ctime_updates); > > > +static DEFINE_PER_CPU(unsigned long, mg_fine_stamps); > > > +static DEFINE_PER_CPU(unsigned long, mg_floor_swaps); > > > +static DEFINE_PER_CPU(unsigned long, mg_ctime_swaps); > > > > Should this all get switched off if CONFIG_DEBUG_FS=n? > > > > --D > > > > Sure, why not. That's simple enough to do. > > I pushed an updated mgtime branch to my git tree. Here's the updated > patch that's the only difference: > > https://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux.git/commit/?h=mgtime&id=ee7fe6e9c0598754861c8620230f15f3de538ca5 > > Seems to build OK both with and without CONFIG_DEBUG_FS. Looks good to me. Feel free to add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza > > > > > > > static struct kmem_cache *inode_cachep __ro_after_init; > > > > > > @@ -101,6 +107,42 @@ static inline long get_nr_inodes_unused(void) > > > return sum < 0 ? 0 : sum; > > > } > > > > > > +static long get_mg_ctime_updates(void) > > > +{ > > > + int i; > > > + long sum = 0; > > > + for_each_possible_cpu(i) > > > + sum += per_cpu(mg_ctime_updates, i); > > > + return sum < 0 ? 0 : sum; > > > +} > > > + > > > +static long get_mg_fine_stamps(void) > > > +{ > > > + int i; > > > + long sum = 0; > > > + for_each_possible_cpu(i) > > > + sum += per_cpu(mg_fine_stamps, i); > > > + return sum < 0 ? 0 : sum; > > > +} > > > + > > > +static long get_mg_floor_swaps(void) > > > +{ > > > + int i; > > > + long sum = 0; > > > + for_each_possible_cpu(i) > > > + sum += per_cpu(mg_floor_swaps, i); > > > + return sum < 0 ? 0 : sum; > > > +} > > > + > > > +static long get_mg_ctime_swaps(void) > > > +{ > > > + int i; > > > + long sum = 0; > > > + for_each_possible_cpu(i) > > > + sum += per_cpu(mg_ctime_swaps, i); > > > + return sum < 0 ? 0 : sum; > > > +} > > > + > > > long get_nr_dirty_inodes(void) > > > { > > > /* not actually dirty inodes, but a wild approximation */ > > > @@ -2655,6 +2697,7 @@ struct timespec64 > > > inode_set_ctime_current(struct inode *inode) > > > > > > /* Get a fine-grained time */ > > > fine = ktime_get(); > > > + this_cpu_inc(mg_fine_stamps); > > > > > > /* > > > * If the cmpxchg works, we take the new > > > floor value. If > > > @@ -2663,11 +2706,14 @@ 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)) > > > + this_cpu_inc(mg_floor_swaps); > > > + else > > > fine = old; > > > now = ktime_mono_to_real(fine); > > > } > > > } > > > + this_cpu_inc(mg_ctime_updates); > > > now_ts = timestamp_truncate(ktime_to_timespec64(now), > > > inode); > > > cur = cns; > > > > > > @@ -2682,6 +2728,7 @@ 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); > > > + this_cpu_inc(mg_ctime_swaps); > > > } else { > > > /* > > > * Was the change due to someone marking the old > > > ctime QUERIED? > > > @@ -2751,3 +2798,24 @@ 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) > > > +{ > > > + long ctime_updates = get_mg_ctime_updates(); > > > + long ctime_swaps = get_mg_ctime_swaps(); > > > + long fine_stamps = get_mg_fine_stamps(); > > > + long floor_swaps = 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); > > > > > > -- > > > 2.45.2 > > > > > > > > -- > Jeff Layton <jlayton@xxxxxxxxxx> > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
