Hi everyone, I noticed that browsing Object take several seconds (5s on my machine). Evaluate Nautilus openOnClass: Object. After profiling, I found it's because of ClassWidget>>setCachedHierarchyClass: that calls SortHierarchically class>>buildHierarchyForClasses: with a big collection of classes. But the browser opens on the package view by default, not the hierarchy view. So if I replace: ClassWidget>>showHierarchy: anObject showHierarchy := anObject. self selectedClass ifNotNil:[: class | self setCachedHierarchyClass: class] by: ClassWidget>>showHierarchy: aBoolean (showHierarchy := aBoolean) ifTrue: [ self selectedClass ifNotNil: [ :class | self setCachedHierarchyClass: class] ] it solves the problem. But I don't know that part of the system well and I don't know if it's the correct thing to do or if we should try to improve performances of SortHierarchically instead. So tell me what you think about it. Here is the bug entry: https://pharo.fogbugz.com/f/cases/13795/Browsing-certain-classes-takes-sever... Thanks, Camille