Re: [PATCH v1 0/4] ceph: forward average read/write/metadata latency

[Jeff Layton <jlayton@redhat.com>]

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?

Thanks,
-- 
Jeff Layton <jlayton@redhat.com>