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CL 214239 improved type printing, but introduced performance regressions: 3-5% memory increase, 1-2% CPU time increase. There were two primary sources of the memory regression: * allocating a bytes.Buffer for every type to print * always printing to that buffer, even when we could return a constant string This change addresses both of those regressions. The sync.Pool allows buffer re-use. String interning prevents allocation for re-used strings. It addresses some, but not all, of the CPU time regression. Memory performance impact vs master: name old alloc/op new alloc/op delta Template 37.6MB ± 0% 36.3MB ± 0% -3.30% (p=0.008 n=5+5) Unicode 28.7MB ± 0% 28.3MB ± 0% -1.55% (p=0.008 n=5+5) GoTypes 127MB ± 0% 122MB ± 0% -4.38% (p=0.008 n=5+5) Compiler 584MB ± 0% 568MB ± 0% -2.72% (p=0.008 n=5+5) SSA 1.99GB ± 0% 1.95GB ± 0% -1.97% (p=0.008 n=5+5) Flate 23.5MB ± 0% 22.8MB ± 0% -2.84% (p=0.008 n=5+5) GoParser 29.2MB ± 0% 28.0MB ± 0% -4.17% (p=0.008 n=5+5) Reflect 81.9MB ± 0% 78.6MB ± 0% -4.09% (p=0.008 n=5+5) Tar 35.3MB ± 0% 34.1MB ± 0% -3.29% (p=0.008 n=5+5) XML 45.5MB ± 0% 44.3MB ± 0% -2.61% (p=0.008 n=5+5) [Geo mean] 82.4MB 79.9MB -3.09% name old allocs/op new allocs/op delta Template 394k ± 0% 363k ± 0% -7.73% (p=0.008 n=5+5) Unicode 340k ± 0% 329k ± 0% -3.25% (p=0.008 n=5+5) GoTypes 1.41M ± 0% 1.28M ± 0% -9.54% (p=0.008 n=5+5) Compiler 5.77M ± 0% 5.39M ± 0% -6.58% (p=0.008 n=5+5) SSA 19.1M ± 0% 18.1M ± 0% -5.13% (p=0.008 n=5+5) Flate 247k ± 0% 228k ± 0% -7.50% (p=0.008 n=5+5) GoParser 325k ± 0% 295k ± 0% -9.24% (p=0.008 n=5+5) Reflect 1.04M ± 0% 0.95M ± 0% -8.48% (p=0.008 n=5+5) Tar 365k ± 0% 336k ± 0% -7.93% (p=0.008 n=5+5) XML 449k ± 0% 417k ± 0% -7.10% (p=0.008 n=5+5) [Geo mean] 882k 818k -7.26% Memory performance going from 52c4488471ed52085a29e173226b3cbd2bf22b20, which is the commit preceding CL 214239, to this change: name old alloc/op new alloc/op delta Template 36.5MB ± 0% 36.3MB ± 0% -0.37% (p=0.008 n=5+5) Unicode 28.3MB ± 0% 28.3MB ± 0% -0.06% (p=0.008 n=5+5) GoTypes 123MB ± 0% 122MB ± 0% -0.64% (p=0.008 n=5+5) Compiler 571MB ± 0% 568MB ± 0% -0.51% (p=0.008 n=5+5) SSA 1.96GB ± 0% 1.95GB ± 0% -0.13% (p=0.008 n=5+5) Flate 22.8MB ± 0% 22.8MB ± 0% ~ (p=0.421 n=5+5) GoParser 28.1MB ± 0% 28.0MB ± 0% -0.37% (p=0.008 n=5+5) Reflect 78.8MB ± 0% 78.6MB ± 0% -0.32% (p=0.008 n=5+5) Tar 34.3MB ± 0% 34.1MB ± 0% -0.35% (p=0.008 n=5+5) XML 44.3MB ± 0% 44.3MB ± 0% +0.05% (p=0.032 n=5+5) [Geo mean] 80.1MB 79.9MB -0.27% name old allocs/op new allocs/op delta Template 372k ± 0% 363k ± 0% -2.46% (p=0.008 n=5+5) Unicode 333k ± 0% 329k ± 0% -0.97% (p=0.008 n=5+5) GoTypes 1.33M ± 0% 1.28M ± 0% -3.71% (p=0.008 n=5+5) Compiler 5.53M ± 0% 5.39M ± 0% -2.50% (p=0.008 n=5+5) SSA 18.3M ± 0% 18.1M ± 0% -1.22% (p=0.008 n=5+5) Flate 234k ± 0% 228k ± 0% -2.44% (p=0.008 n=5+5) GoParser 305k ± 0% 295k ± 0% -3.23% (p=0.008 n=5+5) Reflect 980k ± 0% 949k ± 0% -3.12% (p=0.008 n=5+5) Tar 345k ± 0% 336k ± 0% -2.69% (p=0.008 n=5+5) XML 425k ± 0% 417k ± 0% -1.72% (p=0.008 n=5+5) [Geo mean] 838k 818k -2.41% Remaining CPU time regression, that is, the change from before CL 214239 to this change: name old time/op new time/op delta Template 208ms ± 2% 209ms ± 1% ~ (p=0.181 n=47+46) Unicode 82.9ms ± 2% 81.9ms ± 2% -1.25% (p=0.000 n=50+48) GoTypes 709ms ± 3% 714ms ± 3% +0.77% (p=0.003 n=48+49) Compiler 3.31s ± 2% 3.32s ± 2% ~ (p=0.271 n=48+48) SSA 10.8s ± 1% 10.9s ± 1% +0.61% (p=0.000 n=46+47) Flate 134ms ± 2% 134ms ± 1% +0.41% (p=0.002 n=48+46) GoParser 166ms ± 2% 167ms ± 2% +0.41% (p=0.010 n=46+48) Reflect 440ms ± 4% 444ms ± 4% +1.05% (p=0.002 n=50+49) Tar 183ms ± 2% 184ms ± 2% ~ (p=0.074 n=45+45) XML 247ms ± 2% 248ms ± 2% +0.67% (p=0.001 n=49+48) [Geo mean] 425ms 427ms +0.34% name old user-time/op new user-time/op delta Template 271ms ± 2% 271ms ± 2% ~ (p=0.654 n=48+48) Unicode 117ms ± 2% 116ms ± 3% ~ (p=0.458 n=47+45) GoTypes 952ms ± 3% 963ms ± 2% +1.11% (p=0.000 n=48+49) Compiler 4.50s ± 5% 4.49s ± 7% ~ (p=0.894 n=50+50) SSA 15.0s ± 2% 15.1s ± 2% +0.46% (p=0.015 n=50+49) Flate 166ms ± 2% 167ms ± 2% +0.40% (p=0.005 n=49+48) GoParser 202ms ± 2% 203ms ± 2% +0.60% (p=0.002 n=49+47) Reflect 583ms ± 3% 588ms ± 3% +0.82% (p=0.001 n=49+46) Tar 223ms ± 2% 224ms ± 2% +0.37% (p=0.046 n=48+46) XML 310ms ± 2% 311ms ± 2% +0.46% (p=0.009 n=50+49) [Geo mean] 554ms 556ms +0.36% Change-Id: I85951a6538373ef4309a2cc366cc1ebaf1f4582d Reviewed-on: https://go-review.googlesource.com/c/go/+/214818 Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org>
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