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From: Venky Shankar <vshankar@redhat.com>
To: jlayton@redhat.com, pdonnell@redhat.com, xiubli@redhat.com
Cc: ceph-devel@vger.kernel.org, Venky Shankar <vshankar@redhat.com>
Subject: [PATCH v2 0/4] ceph: forward average read/write/metadata latency
Date: Tue, 14 Sep 2021 14:18:58 +0530	[thread overview]
Message-ID: <20210914084902.1618064-1-vshankar@redhat.com> (raw)

v2:
  - based on top of ceph-client/testing branch

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 |  20 ++++-----
 fs/ceph/metric.c  | 105 ++++++++++++++++++++++------------------------
 fs/ceph/metric.h  |  68 +++++++++++++++++++-----------
 3 files changed, 104 insertions(+), 89 deletions(-)

-- 
2.31.1


             reply	other threads:[~2021-09-14  8:49 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-14  8:48 Venky Shankar [this message]
2021-09-14  8:48 ` [PATCH v2 1/4] ceph: use "struct ceph_timespec" for r/w/m latencies Venky Shankar
2021-09-14  8:49 ` [PATCH v2 2/4] ceph: track average/stdev r/w/m latency Venky Shankar
2021-09-14 12:52   ` Xiubo Li
2021-09-14 13:03     ` Venky Shankar
2021-09-14 13:09   ` Xiubo Li
2021-09-14 13:30     ` Venky Shankar
2021-09-14 13:45       ` Xiubo Li
2021-09-14 13:52         ` Xiubo Li
2021-09-14 14:00           ` Venky Shankar
2021-09-14 14:10             ` Xiubo Li
2021-09-14 13:53         ` Venky Shankar
2021-09-14 13:58           ` Xiubo Li
2021-09-14 13:13   ` Xiubo Li
2021-09-14 13:32     ` Jeff Layton
2021-09-14 13:32     ` Venky Shankar
2021-09-14  8:49 ` [PATCH v2 3/4] ceph: include average/stddev r/w/m latency in mds metrics Venky Shankar
2021-09-14 13:57   ` Xiubo Li
2021-09-14  8:49 ` [PATCH v2 4/4] ceph: use tracked average r/w/m latencies to display metrics in debugfs Venky Shankar

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