From: Venky Shankar <vshankar@redhat.com>
To: Jeff Layton <jlayton@redhat.com>
Cc: Patrick Donnelly <pdonnell@redhat.com>,
Xiubo Li <xiubli@redhat.com>,
ceph-devel <ceph-devel@vger.kernel.org>
Subject: Re: [PATCH v1 0/4] ceph: forward average read/write/metadata latency
Date: Mon, 13 Sep 2021 21:11:32 +0530 [thread overview]
Message-ID: <CACPzV1=SnZhLo7qq2CQ8U9UHVf1ENsPf=EkqDF2qwQsrF9YNkw@mail.gmail.com> (raw)
In-Reply-To: <a79f35e47a105bb24baa666bca8c7cfe956d5076.camel@redhat.com>
On Mon, Sep 13, 2021 at 8:51 PM Jeff Layton <jlayton@redhat.com> wrote:
>
> On Mon, 2021-09-13 at 11:13 -0400, Jeff Layton wrote:
> > On Mon, 2021-09-13 at 18:43 +0530, Venky Shankar wrote:
> > > Right now, cumulative read/write/metadata latencies are tracked
> > > and are periodically forwarded to the MDS. These meterics are not
> > > particularly useful. A much more useful metric is the average latency
> > > and standard deviation (stdev) which is what this series of patches
> > > aims to do.
> > >
> > > The userspace (libcephfs+tool) changes are here::
> > >
> > > https://github.com/ceph/ceph/pull/41397
> > >
> > > The math involved in keeping track of the average latency and stdev
> > > seems incorrect, so, this series fixes that up too (closely mimics
> > > how its done in userspace with some restrictions obviously) as per::
> > >
> > > NEW_AVG = OLD_AVG + ((latency - OLD_AVG) / total_ops)
> > > NEW_STDEV = SQRT(((OLD_STDEV + (latency - OLD_AVG)*(latency - NEW_AVG)) / (total_ops - 1)))
> > >
> > > Note that the cumulative latencies are still forwarded to the MDS but
> > > the tool (cephfs-top) ignores it altogether.
> > >
> > > Venky Shankar (4):
> > > ceph: use "struct ceph_timespec" for r/w/m latencies
> > > ceph: track average/stdev r/w/m latency
> > > ceph: include average/stddev r/w/m latency in mds metrics
> > > ceph: use tracked average r/w/m latencies to display metrics in
> > > debugfs
> > >
> > > fs/ceph/debugfs.c | 12 +++----
> > > fs/ceph/metric.c | 81 +++++++++++++++++++++++++----------------------
> > > fs/ceph/metric.h | 64 +++++++++++++++++++++++--------------
> > > 3 files changed, 90 insertions(+), 67 deletions(-)
> > >
> >
> > This looks reasonably sane. I'll plan to go ahead and pull this into the
> > testing kernels and do some testing with them. If anyone has objections
> > (Xiubo?) let me know and I can take them out.
> >
> > Thanks,
>
> Hmm...I take it back. There are some non-trivial merge conflicts in this
> series vs. the current testing branch. Venky can you rebase this onto
> the ceph-client/testing branch and resubmit?
Sure, will do.
>
> Thanks,
> --
> Jeff Layton <jlayton@redhat.com>
>
--
Cheers,
Venky
next prev parent reply other threads:[~2021-09-13 15:42 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-13 13:13 [PATCH v1 0/4] ceph: forward average read/write/metadata latency Venky Shankar
2021-09-13 13:13 ` [PATCH v1 1/4] ceph: use "struct ceph_timespec" for r/w/m latencies Venky Shankar
2021-09-13 13:13 ` [PATCH v1 2/4] ceph: track average/stdev r/w/m latency Venky Shankar
2021-09-13 13:13 ` [PATCH v1 3/4] ceph: include average/stddev r/w/m latency in mds metrics Venky Shankar
2021-09-13 13:13 ` [PATCH v1 4/4] ceph: use tracked average r/w/m latencies to display metrics in debugfs Venky Shankar
2021-09-13 15:13 ` [PATCH v1 0/4] ceph: forward average read/write/metadata latency Jeff Layton
2021-09-13 15:21 ` Jeff Layton
2021-09-13 15:41 ` Venky Shankar [this message]
2021-09-14 12:53 ` Xiubo Li
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