On Mon, Feb 28, 2022 at 01:39:08PM +0200, Amir Goldstein wrote:
> Show optional collected per-mount io stats in /proc/<pid>/mountstats
> for filesystems that do not implement their own show_stats() method
> and opted-in to generic per-mount stats with FS_MOUNT_STATS flag.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/mount.h | 1 +
> fs/namespace.c | 2 ++
> fs/proc_namespace.c | 13 +++++++++++++
> 3 files changed, 16 insertions(+)
>
> diff --git a/fs/mount.h b/fs/mount.h
> index f98bf4cd5b1a..2ab6308af78b 100644
> --- a/fs/mount.h
> +++ b/fs/mount.h
> @@ -91,6 +91,7 @@ struct mount {
> int mnt_id; /* mount identifier */
> int mnt_group_id; /* peer group identifier */
> int mnt_expiry_mark; /* true if marked for expiry */
> + time64_t mnt_time; /* time of mount */
> struct hlist_head mnt_pins;
> struct hlist_head mnt_stuck_children;
> } __randomize_layout;
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 3fb8f11a42a1..546f07ed44c5 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -220,6 +220,8 @@ static struct mount *alloc_vfsmnt(const char *name)
> mnt->mnt_count = 1;
> mnt->mnt_writers = 0;
> #endif
> + /* For proc/<pid>/mountstats */
> + mnt->mnt_time = ktime_get_seconds();
>
> INIT_HLIST_NODE(&mnt->mnt_hash);
> INIT_LIST_HEAD(&mnt->mnt_child);
> diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
> index 49650e54d2f8..d744fb8543f5 100644
> --- a/fs/proc_namespace.c
> +++ b/fs/proc_namespace.c
> @@ -232,6 +232,19 @@ static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
> if (sb->s_op->show_stats) {
> seq_putc(m, ' ');
> err = sb->s_op->show_stats(m, mnt_path.dentry);
> + } else if (mnt_has_stats(mnt)) {
> + /* Similar to /proc/<pid>/io */
> + seq_printf(m, "\n"
> + "\ttimes: %lld %lld\n"
> + "\trchar: %lld\n"
> + "\twchar: %lld\n"
> + "\tsyscr: %lld\n"
> + "\tsyscw: %lld\n",
> + r->mnt_time, ktime_get_seconds(),
> + mnt_iostats_counter_read(r, MNTIOS_CHARS_RD),
> + mnt_iostats_counter_read(r, MNTIOS_CHARS_WR),
> + mnt_iostats_counter_read(r, MNTIOS_SYSCALLS_RD),
> + mnt_iostats_counter_read(r, MNTIOS_SYSCALLS_WR));
This doesn't scale as {cpus, mounts, counters, read frequency}
matrix explodes. Please iterate the per-mount per cpu counters
once, adding up all counters in one pass to an array on stack, then
print them all from the array.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
