Sorry, I shouldn't have assumed that everyone know what the Computer Language Benchmark Game was.
There's a set of 10 toy benchmarks written in 30 different languages that are available here: http://benchmarksgame.alioth.debian.org/ The webpage also lets you see the results of regular performance runs and see how the various programs stack up against each other. As usual with small benchmarks, there are lots of ways in which the programs aren't realistic. After dispatch became available on Linux with Swift 3, I had a side project of going through the Swift implementations and adding concurrency to a few Swift programs that didn't have it already. regex-dna is the main outlier for Swift (which is why I had profiled it). There's enough ARC overhead that using dispatch actually made it slower... The sequential version for of regex-dna for Swift is: http://benchmarksgame.alioth.debian.org/u64q/program.php?test=regexdna&lang=swift&id=2 My slower concurrent version is: http://benchmarksgame.alioth.debian.org/u64q/program.php?test=regexdna&lang=swift&id=3 I suspect that the main fix for improving the performance of this program is actually doing something in CoreFoundation, but I got sidetracked and didn't finish looking into it. --dave From: Michael Gottesman <mgottes...@apple.com> To: David P Grove/Watson/IBM@IBMUS Cc: Jiho Choi <jray...@gmail.com>, swift-dev <swift-dev@swift.org> Date: 02/17/2017 05:32 PM Subject: Re: [swift-dev] Profiling ARC Sent by: mgottes...@apple.com On Feb 17, 2017, at 11:30 AM, David P Grove via swift-dev < swift-dev@swift.org> wrote: swift-dev-boun...@swift.org wrote on 02/16/2017 09:48:28 PM: > > I was curious about the overhead of ARC and started profiling some > benchmarks found in the Computer Language Benchmark Game (http:// > benchmarksgame.alioth.debian.org/u64q/measurements.php?lang=swift). > So far, it seems that ARC sequence optimization is surprisingly good > and most benchmarks don't have to perform ARC operations as often as > I expected. I have some questions regarding this finding. > > I compiled all benchmarks with "-O -wmo" flags and counted the > number of calls to ARC runtime (e.g., swift_rt_swift_retain) using Pin. > > 1. Reference counting is considered to have high overhead due to > frequent counting operations which also have to be atomic. At least > for the benchmarks I tested, it is not the case and there is almost > no overhead. Is it expected behavior? Or is it because the > benchmarks are too simple (they are all single-file programs)? How > do you estimate the overhead of ARC would be? > hmm, I wonder if your method of profiling is really finding all the ARC operations. The Swift version of regex-dna is about 25x slower than the Java version (on Linux). I looked at some prof profiles about a month ago and at the time roughly 80% of all execution samples were attributed to swift_retain/swift_release operations coming from CoreFoundation's regex implementation. Question. Where is this regex-dna benchmark, is it in the swift benchmark suite? --dave (See attached file: regex-dna.svg) <regex-dna.svg>_______________________________________________ swift-dev mailing list swift-dev@swift.org https://lists.swift.org/mailman/listinfo/swift-dev
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