1. Double-click text selection in both Squeak and Pharo shows a 75-100 ms latency (eye-balled, estimated) between end of double click (button up on second click) and time of highlighting of selected text. It could be as low as 60 ms, but I doubt it, and that’s still too long. I can’t track the latency in VW 8.3.2. It’s too short, probably 30 ms or less, and is under my noise floor. Notepad latencies are even lower. The difference between VW and Notepad is not enough to complain about. Neither is noticeable in passing. The difference between VW and Pharo/Squeak latencies is a little painful/distracting. It’s very much in your face, and you are keenly aware that you are waiting for something to happen before you can resume your thoughts about the code.
2. Stepping in the Pharo debugger is slow (Squeak is fine). The latencies between the step-click event and selection of the next evaluable is a solid 100 ms (again estimated). Feels more like 150-175 ms much of the time. This is actually hard to work with. Neither of these unequivocally demonstrates VM performance. I know. This comment is not about the VM. VM performance is another issue. This comment is only about general usability as a function of the latencies, whatever the cause. Both are more likely to derive from overall GUI architecture. Yup. In particular, VW’s display architecture is a direct stimulus-response i/o model where input results in a transformation producing immediate rendering, whereas Morphic is an animation architecture where input results in a new state but no rendering. The Morphic GUI is rendered separately on every “step” of the system. Okay. Hence graphics output necessarily lags input on Morphic. So these speed differences have nothing to do with vm performance and everything to do with GUI architecture. Both Squeak and Pharo show the same delay for text selection latency. The architecture difference is not likely causing that. How do we index or look up the word rectangle to render? I’m think that is more likely the cause. Is a map created at method compile time and updated after text is moved during edits? Where is VisualWorks significantly faster than either Squeak or Pharo? VW 8.3.2 faster: 1. Text selection. 2. Repeat-key rate in VW is smoother (not perfect; I see a few pauses). Pharo’s repeat-key rate is the same or a little slower, there are more pauses, and distribution of those pause-times is slightly wider for Pharo 9, as if event flow isn’t as smooth as it could be (because text/cursor rendering is a not efficient?). This is a minor issue, not a practical problem. I did the test in a workspace in both cases. Pharo 9 same or faster: Everything else in the GUI, like window openings/closings, menu openings/closings work at nearly the same speed, or Pharo 9 is faster. Opening a system browser in VW 8.3.2 and Pharo 9 takes about the same time. If you scrutinize, you can see that Pharo system browser open times are often about 2/3 to 4/5 of the VW times. This action is never faster in VW. Popup menus in Pharo 9 are noticeably faster than those in VW 8.3.2. Instant--delightful. Specifically which VisualWorks VM or lower level facilities are much faster than the Cog VM? Do you have benchmarks? No, I don’t, but I find the subject interesting, and would like to pursue it. I’m trying to get some pressing work done in VW (as I contemplate jumping ship to Pharo/Squeak). It’s not a good time for excursions, but here I am playing with Squeak/Pharo, anyway. I want to dig deeper at some future date. Do you have a specific procedure you like to use when benchmarking the VW VM? Any VM. Express the benchmark as a block. If the benchmark is not trying to measure JIT and/or GC overhead then before the block is run make sure to put the vm in some initialized state wrt hitting and/or GC, eg by voiding the JIT code cache, How is the JIT code cache cleared? and/or forcing a scavenge or a global GC. Then run the block twice, reporting it’s second iteration, to ensure all code is JITted. Okay, so the above procedure tests execution-engine efficiency apart from JIT and GC efficiency. If attempting to measure JIT and/or GC overhead then do the same wet getting the vm to some baseline consistent initial state Baseline state: the only thing that comes to mind here is Collect All Garbage. and then ensure, through the relevant introspection primitives, What are these? What state features am I introspecting after the test? Sizes of heap subspaces? I can do Time microsecondsToRun: on the blocks. that after the benchmark has run the events desired to be benchmarked have actually taken place. I’m thinking most checks on state will involve running more Smalltalk, not just primitives. If a micobenchmark then ensure that eg loop, block invocation, arithmetic, overheads are either minimised wrt the code being benchmarked or subtracted from the code being benchmarked. Okay. i.e. make sure the benchmark is repeatable (benchmark an initial used state). make sure the benchmark measures what is intended to be benchmarked and not some overhead. Right. I don’t see how to guarantee some known starting state except to collect all garbage. Shaping
