3 ms·
> Median latency is a completely useless number. There is literally no use for it, ever. Satan invented median latency to confuse people, because it lies to you
by yxhuvud 11y ago
> Median latency is a completely useless number. There is literally no use for it, ever. Satan invented median latency to confuse people, because it lies to you and whispers sweet nothings in your ear. Averaging latencies in your monitoring leaves the outliers out in the cold because you will never see them, and tail latency is way more important for user experience.
Umm, you do not get the median latency by averaging anything. Median latency is just the 50th percentile. It is definitely not one of the interesting ones to reason about or care about improving, but not valueless to measure. It is interesting to have if you are graphing your latency curves, to make an example.
- deleted 11y ago[deleted]
- jsmthrowaway 11y agoI think if you reread my comment you'll find that what you're saying does not actually disagree and is a restating of what I said.
- yxhuvud 11y agoIt is not. Your comment confuses the median with the mean latency. The comment you replied to did not mention using averages - it mentioned only using the median. You introduced scathing critique of using averages when those are only used for means and therefore totally irrelevant here (even if I totally agree that people that use them should be educated. But that wasn't the case here).
- jsmthrowaway 11y agoI actually don't, and you're reacting to the use of "averaging" as a verb. That's why I encouraged you to reread. When you're discarding 50% of the samples in a 50th percentile median, I think "averaging" is an acceptable verb to proxy the situation in English since "medianing" isn't a word. I could have said "computing the median," but that's just tedious. Notice later in the comment I say average/median, implying that they are separate but related concepts. I think it's safe to assume that someone who can conversationally use the word "quantile" is not confusing median with mean. You're assuming that my (intentional) selection of a lower-fidelity term to describe a concept, which I carefully illustrated with ancillary points to give specificity to said concept, demonstrates a misunderstanding of the very field I'm explaining. That is pretty obviously wrong and a bit condescending. We agree, which is what's frustrating. You're just latching on to a pedantic correction of my point, and rather than belabor that correction I encouraged you to reread to see that we do actually agree. Now, I do see average latency far more often than I'd care to admit, which is why I got lazy and just said "average" at the end there once I started referring to generality instead of specificity, but I think it's pretty clear that I understand the distinction regardless.
- skj 11y agoIn statistician-land, the median is simply one way of averaging, as is the mean. Introducing (or at least using) the extra term takes care of some ambiguity.