> 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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