3 ms·
> you can't chart a centile, Why? If you have servers with millions of qps, the graph would show the 99% latency over, say, a second or ten. I think this grap
by petters 9y ago
> you can't chart a centile,
Why? If you have servers with millions of qps, the graph would show the 99% latency over, say, a second or ten.
I think this graph is pretty standard? But I'm happy for suggestions of better ones.
- user5994461 9y agoThere are constant variations in the environment that are more significant than the tiny effect you are trying to measure.
- jimktrains2 9y agoThere are many statical tests that can be used in these situations and have been honest over the years for use in scientific research. For example, chi-squared and if you can quantify the error distribution and it's normal, student's t-test.
- microcolonel 9y agoWell, more accurately you could chart a centile, but it would hide the very latency patterns you're looking for. The outliers in a given time bucket are the important data. If you're looking at one bucket, it could be useful to do a centile (though 99th is not really high enough to be meaningful), but if you're charting centile buckets, then you're missing the real latency spikes. For all we know, KCM/KTLS generates the highest peak latency, but fewer times per bucket. That difference would completely change the interpretation of these data. If userspace data frame handling produces higher 99th percentile latency, that does not tell us anything about its maximum latency. Further, if we're looking at the 99th percentile, 1/100 data frames have latency higher than that percentile, this will happen hundreds, thousands, or millions of times per second depending on your interface bandwidth and typical frame size!