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Daniel Templeton commented on YARN-7391: ---------------------------------------- Do you have a particular scenario where the log-based weight isn't given reasonable results? My concern would be that a sqrt-based weight would allow a big-memory app to starve out smaller apps. Without a motivating issue, I'm not super excited about changing this part of the code. On a tangentially related note, I was profiling the scheduler yesterday and noticed that we spend a ton on our scheduling time waiting for the lock in this method. Looks like a good candidate for caching in {{FSAppAttempt}}. > Consider square root instead of natural log for size-based weight > ----------------------------------------------------------------- > > Key: YARN-7391 > URL: https://issues.apache.org/jira/browse/YARN-7391 > Project: Hadoop YARN > Issue Type: Improvement > Components: fairscheduler > Affects Versions: 3.0.0-beta1 > Reporter: Steven Rand > > Currently for size-based weight, we compute the weight of an app using this > code from > https://github.com/apache/hadoop/blob/trunk/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FairScheduler.java#L377: > {code} > if (sizeBasedWeight) { > // Set weight based on current memory demand > weight = Math.log1p(app.getDemand().getMemorySize()) / Math.log(2); > } > {code} > Because the natural log function grows slowly, the weights of two apps with > hugely different memory demands can be quite similar. For example, {{weight}} > evaluates to 14.3 for an app with a demand of 20 GB, and evaluates to 19.9 > for an app with a demand of 1000 GB. The app with the much larger demand will > still have a higher weight, but not by a large amount relative to the sum of > those weights. > I think it's worth considering a switch to a square root function, which will > grow more quickly. In the above example, the app with a demand of 20 GB now > has a weight of 143, while the app with a demand of 1000 GB now has a weight > of 1012. These weights seem more reasonable relative to each other given the > difference in demand between the two apps. > The above example is admittedly a bit extreme, but I believe that a square > root function would also produce reasonable results in general. > The code I have in mind would look something like: > {code} > if (sizeBasedWeight) { > // Set weight based on current memory demand > weight = Math.sqrt(app.getDemand().getMemorySize()); > } > {code} > Would people be comfortable with this change? -- This message was sent by Atlassian JIRA (v6.4.14#64029) --------------------------------------------------------------------- To unsubscribe, e-mail: yarn-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: yarn-issues-h...@hadoop.apache.org