Hi,
Bringing back performance histograms:
https://github.com/ceph/ceph/pull/12829
I've updated the PR, rebased on master and made internal changes less
aggressive.
All ctest tests passing and I haven't seen any issues with performance
(and I can actually see much better what the performance characteristics are
Waiting for your comments,
Bartek
Looking
On 01/09/2017 12:27 PM, Bartłomiej Święcki wrote:
Hi,
I've made a simple implementation of performance histograms.
Implementation is not very sophisticated
but I think it could be a good start for more detailed discussion.
Here's the PR: https://github.com/ceph/ceph/pull/12829
Regards,
Bartek
On 11/28/2016 05:22 PM, Bartłomiej Święcki wrote:
Hi,
Currently we can query OSD for op latency but it's given as an
average. Average may not give
the bets information in this case - i.e. spikes can easily get hidden
there.
Instead of an average we could easily do a simple histogram -
quantize the latency into
predefined set of time intervals, for each of them have a simple
performance counter,
at each op increase one of them. Since those are per OSD, we could
have pretty high resolution
with fractional memory usage, performance impact should be negligible
since only one (two if split
into read and write) of those counters would be incremented per one
osd op.
In addition we could also do this in 2D - each counter matching given
latency range and op size range.
having such 2D table would show both latency histogram, request size
histogram and combinations of those
(i.e. latency histogram of ~4k ops only).
What do you think about this idea? I can prepare some code - a simple
proof of concept looks really
straightforward to implement.
Bartek
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