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Posted to notifications@couchdb.apache.org by "nickva (via GitHub)" <gi...@apache.org> on 2023/05/23 03:02:53 UTC
[GitHub] [couchdb] nickva opened a new pull request, #4614: Use milliseconds for fsync time histogram
nickva opened a new pull request, #4614:
URL: https://github.com/apache/couchdb/pull/4614
Most of our histograms are in milliseconds. Don't deviate from that with the new fsync.time metric so make it use milliseconds as well. It turns out fractional histogram values are allowed, so we can still get the sub-millisecond precision for faster disks that way.
Example of usage during: `fabric_bench:go(#{docs=>50000, batch_size=>100}).`
```
couch_stats:sample([fsync, time]).
[{min,8.303},
{max,134.124},
{arithmetic_mean,49.3490064102564},
{geometric_mean,42.939511193319994},
{harmonic_mean,37.05011500299417},
{median,43.198},
{variance,654.1673972451199},
{standard_deviation,25.57669637082006},
{skewness,0.7276971171556265},
{kurtosis,-0.021701320829371706},
{percentile,[{50,43.198},
{75,63.858},
{90,81.22},
{95,97.231},
{99,114.86},
{999,134.124}]},
{histogram,[{25.303,48},
{48.303,40},
{68.303,38},
{78.303,4},
{98.303,18},
{118.303,7},
{128.303,0},
{148.303,1}]},
{n,156}]
```
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[GitHub] [couchdb] rnewson commented on pull request #4614: Use milliseconds for fsync time histogram
Posted by "rnewson (via GitHub)" <gi...@apache.org>.
rnewson commented on PR #4614:
URL: https://github.com/apache/couchdb/pull/4614#issuecomment-1559509200
rather, update the comment to say "fractional milliseconds" not "fractional microseconds"
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[GitHub] [couchdb] nickva commented on pull request #4614: Use milliseconds for fsync time histogram
Posted by "nickva (via GitHub)" <gi...@apache.org>.
nickva commented on PR #4614:
URL: https://github.com/apache/couchdb/pull/4614#issuecomment-1558461570
`{median,0.667},` very nice!
Even P90 6 vs 81 msec on my machine is quite nice.
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[GitHub] [couchdb] nickva commented on pull request #4614: Use milliseconds for fsync time histogram
Posted by "nickva (via GitHub)" <gi...@apache.org>.
nickva commented on PR #4614:
URL: https://github.com/apache/couchdb/pull/4614#issuecomment-1559502725
@rnewson `erlang:convert_time_unit/3` would have yielded an integer number milliseconds and we would have lost the sub-millisecond precision. However an improvement could be to collect the data in native, compute the dt (still in native), convert to nanoseconds (as integer) then divide by 1e6 to yield a millisecond floating point value.
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[GitHub] [couchdb] rnewson commented on pull request #4614: Use milliseconds for fsync time histogram
Posted by "rnewson (via GitHub)" <gi...@apache.org>.
rnewson commented on PR #4614:
URL: https://github.com/apache/couchdb/pull/4614#issuecomment-1559505849
A comment in the code to that effect would help, and maybe prevent a future "fix" that would break that.
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[GitHub] [couchdb] nickva commented on pull request #4614: Use milliseconds for fsync time histogram
Posted by "nickva (via GitHub)" <gi...@apache.org>.
nickva commented on PR #4614:
URL: https://github.com/apache/couchdb/pull/4614#issuecomment-1559669453
Improved it a bit in https://github.com/apache/couchdb/pull/4616
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[GitHub] [couchdb] nickva commented on pull request #4614: Use milliseconds for fsync time histogram
Posted by "nickva (via GitHub)" <gi...@apache.org>.
nickva commented on PR #4614:
URL: https://github.com/apache/couchdb/pull/4614#issuecomment-1559522931
Good idea
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[GitHub] [couchdb] nickva merged pull request #4614: Use milliseconds for fsync time histogram
Posted by "nickva (via GitHub)" <gi...@apache.org>.
nickva merged PR #4614:
URL: https://github.com/apache/couchdb/pull/4614
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[GitHub] [couchdb] rnewson commented on pull request #4614: Use milliseconds for fsync time histogram
Posted by "rnewson (via GitHub)" <gi...@apache.org>.
rnewson commented on PR #4614:
URL: https://github.com/apache/couchdb/pull/4614#issuecomment-1558640481
why didn't we use native units for T0 and T1 and then convert_time_unit at the end?
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