linux-kernel - Re: [PATCH] ceph: show max caps in debugfs caps file

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Date:   Thu, 21 May 2020 07:09:52 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Yanhu Cao <gmayyyha@...il.com>
Cc:     idryomov@...il.com, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ceph: show max caps in debugfs caps file

On Thu, 2020-05-21 at 17:38 +0800, Yanhu Cao wrote:
>         before
>         ------
>         total           1026
>         avail           1024
>         used            2
>         reserved        0
>         min             1024
> 
>         after
>         ------
>         total           1026
>         avail           1024
>         used            2
>         max             2048
>         reserved        0
>         min             1024
> 
> Signed-off-by: Yanhu Cao <gmayyyha@...il.com>
> ---
>  fs/ceph/caps.c    | 6 ++++--
>  fs/ceph/debugfs.c | 7 ++++---
>  fs/ceph/super.h   | 2 +-
>  3 files changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> index 5f3aa4d607de..e2c759a2ef35 100644
> --- a/fs/ceph/caps.c
> +++ b/fs/ceph/caps.c
> @@ -404,8 +404,8 @@ void ceph_put_cap(struct ceph_mds_client *mdsc, struct ceph_cap *cap)
>  }
>  
>  void ceph_reservation_status(struct ceph_fs_client *fsc,
> -			     int *total, int *avail, int *used, int *reserved,
> -			     int *min)
> +			     int *total, int *avail, int *used, int *max,
> +			     int *reserved, int *min)
>  {
>  	struct ceph_mds_client *mdsc = fsc->mdsc;
>  
> @@ -417,6 +417,8 @@ void ceph_reservation_status(struct ceph_fs_client *fsc,
>  		*avail = mdsc->caps_avail_count;
>  	if (used)
>  		*used = mdsc->caps_use_count;
> +	if (max)
> +		*max = mdsc->caps_use_max;

Can you lay out what value this will provide? I'm not convinced that
this information is really that helpful:

mdsc->caps_use_max is just set to the value of the "caps_max" mount
option, and that information is displayed in /proc/mounts if it's not
set to the default.

What might be more interesting is to track the most recent "max_caps"
value sent by the MDS (see the CEPH_SESSION_RECALL_STATE message
handling). Tracking that would give us a more dynamic view of the
current maximum requested by the MDS, which is often going to be less
than what "caps_max" was set to at mount time.

>  	if (reserved)
>  		*reserved = mdsc->caps_reserve_count;
>  	if (min)
> diff --git a/fs/ceph/debugfs.c b/fs/ceph/debugfs.c
> index 481ac97b4d25..942004376588 100644
> --- a/fs/ceph/debugfs.c
> +++ b/fs/ceph/debugfs.c
> @@ -138,16 +138,17 @@ static int caps_show(struct seq_file *s, void *p)
>  {
>  	struct ceph_fs_client *fsc = s->private;
>  	struct ceph_mds_client *mdsc = fsc->mdsc;
> -	int total, avail, used, reserved, min, i;
> +	int total, avail, used, max, reserved, min, i;
>  	struct cap_wait	*cw;
>  
> -	ceph_reservation_status(fsc, &total, &avail, &used, &reserved, &min);
> +	ceph_reservation_status(fsc, &total, &avail, &used, &max,
> +				&reserved, &min);
>  	seq_printf(s, "total\t\t%d\n"
>  		   "avail\t\t%d\n"
>  		   "used\t\t%d\n"
>  		   "reserved\t%d\n"
>  		   "min\t\t%d\n\n",
> -		   total, avail, used, reserved, min);
> +		   total, avail, used, max, reserved, min);
>  	seq_printf(s, "ino                issued           implemented\n");
>  	seq_printf(s, "-----------------------------------------------\n");
>  
> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> index 60aac3aee055..79aa42d9336c 100644
> --- a/fs/ceph/super.h
> +++ b/fs/ceph/super.h
> @@ -700,7 +700,7 @@ extern void ceph_unreserve_caps(struct ceph_mds_client *mdsc,
>  			       struct ceph_cap_reservation *ctx);
>  extern void ceph_reservation_status(struct ceph_fs_client *client,
>  				    int *total, int *avail, int *used,
> -				    int *reserved, int *min);
> +				    int *max, int *reserved, int *min);
>  
>  
>  

-- 
Jeff Layton <jlayton@...nel.org>