linux-kernel - Re: [RFC PATCH] ceph: add remote object copy counter to fs client

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Date:   Thu, 21 Oct 2021 12:18:28 -0400
From:   Patrick Donnelly <pdonnell@...hat.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Luís Henriques <lhenriques@...e.de>,
        Ilya Dryomov <idryomov@...il.com>,
        Ceph Development <ceph-devel@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] ceph: add remote object copy counter to fs client

On Thu, Oct 21, 2021 at 11:44 AM Jeff Layton <jlayton@...nel.org> wrote:
>
> On Thu, 2021-10-21 at 09:52 -0400, Patrick Donnelly wrote:
> > On Wed, Oct 20, 2021 at 12:27 PM Jeff Layton <jlayton@...nel.org> wrote:
> > >
> > > On Wed, 2021-10-20 at 15:37 +0100, Luís Henriques wrote:
> > > > This counter will keep track of the number of remote object copies done on
> > > > copy_file_range syscalls.  This counter will be filesystem per-client, and
> > > > can be accessed from the client debugfs directory.
> > > >
> > > > Cc: Patrick Donnelly <pdonnell@...hat.com>
> > > > Signed-off-by: Luís Henriques <lhenriques@...e.de>
> > > > ---
> > > > This is an RFC to reply to Patrick's request in [0].  Note that I'm not
> > > > 100% sure about the usefulness of this patch, or if this is the best way
> > > > to provide the functionality Patrick requested.  Anyway, this is just to
> > > > get some feedback, hence the RFC.
> > > >
> > > > Cheers,
> > > > --
> > > > Luís
> > > >
> > > > [0] https://github.com/ceph/ceph/pull/42720
> > > >
> > >
> > > I think this would be better integrated into the stats infrastructure.
> > >
> > > Maybe you could add a new set of "copy" stats to struct
> > > ceph_client_metric that tracks the total copy operations done, their
> > > size and latency (similar to read and write ops)?
> >
> > I think it's a good idea to integrate this into "stats" but I think a
> > local debugfs file for some counters is still useful. The "stats"
> > module is immature at this time and I'd rather not build any qa tests
> > (yet) that rely on it.
> >
> > Can we generalize this patch-set to a file named "op_counters" or
> > similar and additionally add other OSD ops performed by the kclient?
> >
>
>
> Tracking this sort of thing is the main purpose of the stats code. I'm
> really not keen on adding a whole separate set of files for reporting
> this.

Maybe I'm confused. Is there some "file" which is already used for
this type of debugging information? Or do you mean the code for
sending stats to the MDS to support cephfs-top?

> What's the specific problem with relying on the data in debugfs
> "metrics" file?

Maybe no problem? I wasn't aware of a "metrics" file.

-- 
Patrick Donnelly, Ph.D.
He / Him / His
Principal Software Engineer
Red Hat, Inc.
GPG: 19F28A586F808C2402351B93C3301A3E258DD79D