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Austin Clements beedb1ec33 runtime: add pcvalue cache to improve stack scan speed The cost of scanning large stacks is currently dominated by the time spent looking up and decoding the pcvalue table. However, large stacks are usually large not because they contain calls to many different functions, but because they contain many calls to the same, small set of recursive functions. Hence, walking large stacks tends to make the same pcvalue queries many times. Based on this observation, this commit adds a small, very simple, and fast cache in front of pcvalue lookup. We thread this cache down from operations that make many pcvalue calls, such as gentraceback, stack scanning, and stack adjusting. This simple cache works well because it has minimal overhead when it's not effective. I also tried a hashed direct-map cache, CLOCK-based replacement, round-robin replacement, and round-robin with lookups disabled until there had been at least 16 probes, but none of these approaches had obvious wins over the random replacement policy in this commit. This nearly doubles the overall performance of the deep stack test program from issue #10898: name old time/op new time/op delta Issue10898 16.5s ±12% 9.2s ±12% -44.37% (p=0.008 n=5+5) It's a very slight win on the garbage benchmark: name old time/op new time/op delta XBenchGarbage-12 4.92ms ± 1% 4.89ms ± 1% -0.75% (p=0.000 n=18+19) It's a wash (but doesn't harm performance) on the go1 benchmarks, which don't have particularly deep stacks: name old time/op new time/op delta BinaryTree17-12 3.11s ± 2% 3.20s ± 3% +2.83% (p=0.000 n=17+20) Fannkuch11-12 2.51s ± 1% 2.51s ± 1% -0.22% (p=0.034 n=19+18) FmtFprintfEmpty-12 50.8ns ± 3% 50.6ns ± 2% ~ (p=0.793 n=20+20) FmtFprintfString-12 174ns ± 0% 174ns ± 1% +0.17% (p=0.048 n=15+20) FmtFprintfInt-12 177ns ± 0% 165ns ± 1% -6.99% (p=0.000 n=17+19) FmtFprintfIntInt-12 283ns ± 1% 284ns ± 0% +0.22% (p=0.000 n=18+15) FmtFprintfPrefixedInt-12 243ns ± 1% 244ns ± 1% +0.40% (p=0.000 n=20+19) FmtFprintfFloat-12 318ns ± 0% 319ns ± 0% +0.27% (p=0.001 n=19+20) FmtManyArgs-12 1.12µs ± 0% 1.14µs ± 0% +1.74% (p=0.000 n=19+20) GobDecode-12 8.69ms ± 0% 8.73ms ± 1% +0.46% (p=0.000 n=18+18) GobEncode-12 6.64ms ± 1% 6.61ms ± 1% -0.46% (p=0.000 n=20+20) Gzip-12 323ms ± 2% 319ms ± 1% -1.11% (p=0.000 n=20+20) Gunzip-12 42.8ms ± 0% 42.9ms ± 0% ~ (p=0.158 n=18+20) HTTPClientServer-12 63.3µs ± 1% 63.1µs ± 1% -0.35% (p=0.011 n=20+20) JSONEncode-12 16.9ms ± 1% 17.3ms ± 1% +2.84% (p=0.000 n=19+20) JSONDecode-12 59.7ms ± 0% 58.5ms ± 0% -2.05% (p=0.000 n=19+17) Mandelbrot200-12 3.92ms ± 0% 3.91ms ± 0% -0.16% (p=0.003 n=19+19) GoParse-12 3.79ms ± 2% 3.75ms ± 2% -0.91% (p=0.005 n=20+20) RegexpMatchEasy0_32-12 102ns ± 1% 101ns ± 1% -0.80% (p=0.001 n=14+20) RegexpMatchEasy0_1K-12 337ns ± 1% 346ns ± 1% +2.90% (p=0.000 n=20+19) RegexpMatchEasy1_32-12 84.4ns ± 2% 84.3ns ± 2% ~ (p=0.743 n=20+20) RegexpMatchEasy1_1K-12 502ns ± 1% 505ns ± 0% +0.64% (p=0.000 n=20+20) RegexpMatchMedium_32-12 133ns ± 1% 132ns ± 1% -0.85% (p=0.000 n=20+19) RegexpMatchMedium_1K-12 40.1µs ± 1% 39.8µs ± 1% -0.77% (p=0.000 n=18+18) RegexpMatchHard_32-12 2.08µs ± 1% 2.07µs ± 1% -0.55% (p=0.001 n=18+19) RegexpMatchHard_1K-12 62.4µs ± 1% 62.0µs ± 1% -0.74% (p=0.000 n=19+19) Revcomp-12 545ms ± 2% 545ms ± 3% ~ (p=0.771 n=19+20) Template-12 73.7ms ± 1% 72.0ms ± 0% -2.33% (p=0.000 n=20+18) TimeParse-12 358ns ± 1% 351ns ± 1% -2.07% (p=0.000 n=20+20) TimeFormat-12 369ns ± 1% 356ns ± 0% -3.53% (p=0.000 n=20+18) [Geo mean] 63.5µs 63.2µs -0.41% name old speed new speed delta GobDecode-12 88.3MB/s ± 0% 87.9MB/s ± 0% -0.43% (p=0.000 n=18+17) GobEncode-12 116MB/s ± 1% 116MB/s ± 1% +0.47% (p=0.000 n=20+20) Gzip-12 60.2MB/s ± 2% 60.8MB/s ± 1% +1.13% (p=0.000 n=20+20) Gunzip-12 453MB/s ± 0% 453MB/s ± 0% ~ (p=0.160 n=18+20) JSONEncode-12 115MB/s ± 1% 112MB/s ± 1% -2.76% (p=0.000 n=19+20) JSONDecode-12 32.5MB/s ± 0% 33.2MB/s ± 0% +2.09% (p=0.000 n=19+17) GoParse-12 15.3MB/s ± 2% 15.4MB/s ± 2% +0.92% (p=0.004 n=20+20) RegexpMatchEasy0_32-12 311MB/s ± 1% 314MB/s ± 1% +0.78% (p=0.000 n=15+19) RegexpMatchEasy0_1K-12 3.04GB/s ± 1% 2.95GB/s ± 1% -2.90% (p=0.000 n=19+19) RegexpMatchEasy1_32-12 379MB/s ± 2% 380MB/s ± 2% ~ (p=0.779 n=20+20) RegexpMatchEasy1_1K-12 2.04GB/s ± 1% 2.02GB/s ± 0% -0.62% (p=0.000 n=20+20) RegexpMatchMedium_32-12 7.46MB/s ± 1% 7.53MB/s ± 1% +0.86% (p=0.000 n=20+19) RegexpMatchMedium_1K-12 25.5MB/s ± 1% 25.7MB/s ± 1% +0.78% (p=0.000 n=18+18) RegexpMatchHard_32-12 15.4MB/s ± 1% 15.5MB/s ± 1% +0.62% (p=0.000 n=19+19) RegexpMatchHard_1K-12 16.4MB/s ± 1% 16.5MB/s ± 1% +0.82% (p=0.000 n=20+19) Revcomp-12 466MB/s ± 2% 466MB/s ± 3% ~ (p=0.765 n=19+20) Template-12 26.3MB/s ± 1% 27.0MB/s ± 0% +2.38% (p=0.000 n=20+18) [Geo mean] 97.8MB/s 98.0MB/s +0.23% Change-Id: I281044ae0b24990ba46487cacbc1069493274bc4 Reviewed-on: https://go-review.googlesource.com/13614 Reviewed-by: Keith Randall <khr@golang.org>		2015-10-22 17:48:13 +00:00
api	api: update next.txt	2015-10-12 23:00:00 +00:00
doc	doc: go1.6.txt: -msan option for cmd/{go,compile,link}	2015-10-21 20:42:21 +00:00
lib/time	lib/time: update to IANA release 2015e.	2015-07-22 02:56:31 +00:00
misc	cmd/go: if -msan, pass -fsanitize=memory to cgo builds	2015-10-21 23:52:23 +00:00
src	runtime: add pcvalue cache to improve stack scan speed	2015-10-22 17:48:13 +00:00
test	cmd/compile: "invalid variable name x in type switch", where x is a name of a constant	2015-10-21 04:21:16 +00:00
.gitattributes	.gitattributes: prevent all magic line ending changes	2014-12-12 23:14:54 +00:00
.gitignore	.gitignore: ignore y.output	2015-06-10 00:28:52 +00:00
AUTHORS	A+C: automated updates	2015-09-10 00:59:04 +00:00
CONTRIBUTING.md	doc: suggest security@golang.org for reporting security issues	2015-06-26 09:53:36 +00:00
CONTRIBUTORS	C: Add Brian Gitonga Marete's Google email address (Google CLA).	2015-10-09 15:21:30 +00:00
favicon.ico	godoc: update favicon	2012-10-11 17:02:36 +11:00
LICENSE	doc: update licensing text one more time	2012-03-27 15:09:13 +11:00
PATENTS	LICENSE: separate, change PATENTS text	2010-12-06 16:31:59 -05:00
README.md	readme: emphasize issue tracker is for bugs/proposals	2015-10-02 18:44:14 +00:00
robots.txt	godoc: serve robots.txt raw	2011-02-19 05:46:20 +11:00

README.md

The Go Programming Language

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