Benchmark a call to math.Sqrt(). It is easy. Here is all it takes: https://play.golang.org/p/1XZJsjhpIq
In the assembly output of “go test -v -run=Q -bench=. -gcflags=-S” you can see the SQRT instruction: babar:sqrt mtj$ go test -v -run=Q -bench=. -gcflags=-S # sqrt "".BenchmarkSqrt t=1 size=59 args=0x8 locals=0x0 0x0000 00000 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:10) TEXT "".BenchmarkSqrt(SB), $0-8 0x0000 00000 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:10) FUNCDATA $0, gclocals·a36216b97439c93dafebe03e7f0808b5(SB) 0x0000 00000 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:10) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB) 0x0000 00000 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:11) MOVQ "".b+8(FP), AX 0x0005 00005 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:11) MOVQ $0, CX 0x0007 00007 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:11) MOVQ 216(AX), DX 0x000e 00014 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:11) CMPQ CX, DX 0x0011 00017 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:11) JGE $0, 58 0x0013 00019 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:12) MOVSD "".A(SB), X0 0x001b 00027 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:12) SQRTSD X0, X1 0x001f 00031 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:12) ADDSD X1, X0 0x0023 00035 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:12) MOVSD X0, "".A(SB) 0x002b 00043 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:11) INCQ CX 0x002e 00046 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:11) MOVQ 216(AX), DX 0x0035 00053 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:11) CMPQ CX, DX 0x0038 00056 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:11) JLT $0, 19 0x003a 00058 (/Users/mtj/gocode/src/sqrt/sqrt_test.go:14) RET And the output shows you the time per iteration: babar:sqrt mtj$ go test -v -run=Q -bench=. BenchmarkSqrt-8 100000000 10.9 ns/op PASS ok sqrt 1.113s An empty loop is about 0.75 ns/iteration, so that means: One square root requires about 10.2 nanoseconds to execute. (on my laptop computer) In your hogcpu() function, you have a loop containing a select and a sqrt(). So that means: If select can be implemented in 10.2 nsec, then you’ll be 50% select and 50% sqrt. If 100 nsec, then you’ll be 90.7% select if 1000 nsec, then it will be 98.99% select : there are many ways to implement a non-blocking channel, but not many that are faster than 10.2 nanoseconds. From: <golang-nuts@googlegroups.com> on behalf of <vyasgiridha...@gmail.com> Date: Monday, November 14, 2016 at 6:23 AM To: golang-nuts <golang-nuts@googlegroups.com> Cc: <vyasgiridha...@gmail.com> Subject: Re: [go-nuts] Stressing the system using Why would a select statement take up most of the execution time? Is there another way to implement a non blocking channel? On Monday, November 14, 2016 at 6:01:24 PM UTC+5:30, Michael Jones wrote: This is funny in the sense that my programs are great at stressing the CPU even though I don’t want to! :-) I looked at your hogcpu() function and saw an issue: you busy loop repeats a select statement and a square root. Almost any simple implementation of this will spend all of its time in the select. Put a loop around that math.Sqrt() so that the “hog” routine is doing mostly sqrt() and not mostly select. DO something similar for the hogio and other hog functions. From: <golan...@googlegroups.com> on behalf of <vyasgir...@gmail.com> Date: Monday, November 14, 2016 at 4:06 AM To: golang-nuts <golan...@googlegroups.com> Subject: [go-nuts] Stressing the system using I have been working on this applications to stress the cpu, io and the hard drive. https://github.com/vyasgiridhar/gstress Kind of like stress. But i am unable to achieve high load. This might be due to the scheduling of goroutines. Is there a work around for this? -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
