2 Commits

Author	SHA1	Message	Date
Russ Cox	ba134539c5	runtime: faster entersyscall/exitsyscall ... Replace cas with xadd in scheduler. Suggested by Dmitriy in last code review. Verified with Promela model. When there's actual contention for the atomic word, this avoids the looping that compare-and-swap requires. benchmark old ns/op new ns/op delta runtime_test.BenchmarkSyscall 32 26 -17.08% runtime_test.BenchmarkSyscall-2 155 59 -61.81% runtime_test.BenchmarkSyscall-3 112 52 -52.95% runtime_test.BenchmarkSyscall-4 94 48 -48.57% runtime_test.BenchmarkSyscallWork 871 872 +0.11% runtime_test.BenchmarkSyscallWork-2 481 477 -0.83% runtime_test.BenchmarkSyscallWork-3 338 335 -0.89% runtime_test.BenchmarkSyscallWork-4 263 256 -2.66% R=golang-dev, iant CC=golang-dev https://golang.org/cl/4800047	2011-07-23 12:22:55 -04:00
Russ Cox	025abd530e	runtime: faster entersyscall, exitsyscall ... Uses atomic memory accesses to avoid the need to acquire and release schedlock on fast paths. benchmark old ns/op new ns/op delta runtime_test.BenchmarkSyscall 73 31 -56.63% runtime_test.BenchmarkSyscall-2 538 74 -86.23% runtime_test.BenchmarkSyscall-3 508 103 -79.72% runtime_test.BenchmarkSyscall-4 721 97 -86.52% runtime_test.BenchmarkSyscallWork 920 873 -5.11% runtime_test.BenchmarkSyscallWork-2 516 481 -6.78% runtime_test.BenchmarkSyscallWork-3 550 343 -37.64% runtime_test.BenchmarkSyscallWork-4 632 263 -58.39% (Intel Core i7 L640 2.13 GHz-based Lenovo X201s) Reduced a less artificial server benchmark from 11.5r 12.0u 8.0s to 8.3r 9.1u 1.0s. R=dvyukov, r, bradfitz, r, iant, iant CC=golang-dev https://golang.org/cl/4723042	2011-07-19 11:01:17 -04:00