Steven Rand created YARN-7391: --------------------------------- Summary: 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-dev-unsubscr...@hadoop.apache.org For additional commands, e-mail: yarn-dev-h...@hadoop.apache.org