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Golang SSA performance numbers

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The last thing I'm curious about is compilation time, especially since that's taken a hit or two recently. I know it's easily a net win with numbers like that, but one of my favorite parts of Go is the quick build times, and thus quick iteration times.

Also, since Go is self-compiled, does that mean we'll have to wait until 1.7.1 for the speed improvements to hit the compiler? :-P

I've seen the numbers ~10% slower floating around.

[citation needed]

It's in the mail?!

"Tip compiler (with SSA internal checks off) is about 7% slower than go1.6 to compile net/http (go test -a -c -gcflags=-d=ssa/check/off net/http)"

There's a couple of mentions of it on r/golang[1], though I don't know the validity behind the claims.

[1] https://www.reddit.com/r/golang/comments/48ivj0/devssa_branc...

Well the actual article says 7% slower when compiling the http package.

I'm sure, you can also self-compile the tip. Would be really interesting if this was done for benchmarks.

The linked post gives an estimation :

> "Tip compiler (with SSA internal checks off) is about 7% slower than go1.6 to compile net/http (go test -a -c -gcflags=-d=ssa/check/off net/http)"

... though we may wonder wether the mesured compiler itself was compiled with or without SSA (with 7% being in the ballpark of the expected SSA gains).

The compiler always compiles itself as part of the bootstrap process. The final compiler is built with itself and thus uses its own SSA code generation.

No worries, it will never reach the C and C++ build times which are often measured in minutes and hours.

Compile time is an issue of C++ but not of C.

Yep. A while ago I found myself needing to recompile the Linux kernel for Android, and I was amazed at how fast the build was (I think I last built a kernel in the 90s). It took a lot less time than it takes Android to start up!

I used to work in a project around 2000 that would take 1h build time per architecture/OS combination.

Doing a full build across HP-UX, Aix, Solaris, Red-Hat Linux and Windows for 32 and 64 bits took almost a full day.

EDIT: It was a mix of C and TCL

> Also, since Go is self-compiled, does that mean we'll have to wait until 1.7.1 for the speed improvements to hit the compiler? :-P

No. The compiler compiles itself during the bootstrap phase.

Does the old compiler compile the new compiler after which the new compiler can compile itself? Bootstrapping is incredible.

Yes.

> one of my favorite parts of Go is the quick build times

One of my favourite parts of Go was the quick build times. It used to feel like 'go build' was as fast as 'python'; sadly, that's no longer the case.

Despite the attractive nuisance of "go build", if you're in a fast save-compile-test cycle, you really want "go install". Both do pretty much the same thing (ignoring where the result goes), but install keeps the intermediate package compilations around and does the minimum, whereas build seems to discard them. Put "-v" on both of them and you can see the differences.

I think go build -i does the same without putting the result in the bin dir.

I think this is only true if you're building outside your GOPATH. In my case, build -v, build -v -i, and install all have very similar compile times and only show an edited file being compiled when executed from inside my GOPATH.

Each of those averaged 3.5s in my codebase, for example, on a freshly changed file. go install's second run is 250ms, but I assume that's because it knows the file hasn't changed.

go build -a shows roughly 60 packages and takes 16s, so I would notice if build or install were accidentally recompiling all of them.

Yeah, it got about twice as slow going 1.4 => 1.5, which makes it just slow enough to be annoying.

(It's still much faster than something like C++ though, and feels about the same to me as the (snappy) Objective-C.)

On the flip side, large programs have gone from multi-second GC pauses to unnoticeable. :) I too miss those fast compile times, though.

Can anyone say why the Mandelbrot benchmark, out of all of them, was slower with SSA? Any chance it was just a fluke?

The inner loop went from 15 instructions to 16 because the register optimiser is not finished yet.

Thanks. That's what I asked on the list, but HN was faster :)

I just posted some results there on our own codebase.

Server load time dropped from 25.5s or so to 22.2s; a really nice win on a large and varied codebase for these improvements. I can't imagine not wanting them.

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