• Austin Clements's avatar
    runtime: eliminate one heapBitsForObject from scanobject · 63caec5d
    Austin Clements authored
    scanobject with ptrmask!=nil is only ever called with the base
    pointer of a heap object. Currently, scanobject calls
    heapBitsForObject, which goes to a great deal of trouble to check
    that the pointer points into the heap and to find the base of the
    object it points to, both of which are completely unnecessary in
    this case.
    
    Replace this call to heapBitsForObject with much simpler logic to
    fetch the span and compute the heap bits.
    
    Benchmark results with five runs:
    
    name                                    old mean                new mean        delta
    BenchmarkBinaryTree17              9.21s × (0.95,1.02)     8.55s × (0.91,1.03)  -7.16% (p=0.022)
    BenchmarkFannkuch11                2.65s × (1.00,1.00)     2.62s × (1.00,1.00)  -1.10% (p=0.000)
    BenchmarkFmtFprintfEmpty          73.2ns × (0.99,1.01)    71.7ns × (1.00,1.01)  -1.99% (p=0.004)
    BenchmarkFmtFprintfString          302ns × (0.99,1.00)     292ns × (0.98,1.02)  -3.31% (p=0.020)
    BenchmarkFmtFprintfInt             281ns × (0.98,1.01)     279ns × (0.96,1.02)  ~ (p=0.596)
    BenchmarkFmtFprintfIntInt          482ns × (0.98,1.01)     488ns × (0.95,1.02)  ~ (p=0.419)
    BenchmarkFmtFprintfPrefixedInt     382ns × (0.99,1.01)     365ns × (0.96,1.02)  -4.35% (p=0.015)
    BenchmarkFmtFprintfFloat           475ns × (0.99,1.01)     472ns × (1.00,1.00)  ~ (p=0.108)
    BenchmarkFmtManyArgs              1.89µs × (1.00,1.01)    1.90µs × (0.94,1.02)  ~ (p=0.883)
    BenchmarkGobDecode                22.4ms × (0.99,1.01)    21.9ms × (0.92,1.04)  ~ (p=0.332)
    BenchmarkGobEncode                24.7ms × (0.98,1.02)    23.9ms × (0.87,1.07)  ~ (p=0.407)
    BenchmarkGzip                      397ms × (0.99,1.01)     398ms × (0.99,1.01)  ~ (p=0.718)
    BenchmarkGunzip                   96.7ms × (1.00,1.00)    96.9ms × (1.00,1.00)  ~ (p=0.230)
    BenchmarkHTTPClientServer         71.5µs × (0.98,1.01)    68.5µs × (0.92,1.06)  ~ (p=0.243)
    BenchmarkJSONEncode               46.1ms × (0.98,1.01)    44.9ms × (0.98,1.03)  -2.51% (p=0.040)
    BenchmarkJSONDecode               86.1ms × (0.99,1.01)    86.5ms × (0.99,1.01)  ~ (p=0.343)
    BenchmarkMandelbrot200            4.12ms × (1.00,1.00)    4.13ms × (1.00,1.00)  +0.23% (p=0.000)
    BenchmarkGoParse                  5.89ms × (0.96,1.03)    5.82ms × (0.96,1.04)  ~ (p=0.522)
    BenchmarkRegexpMatchEasy0_32       141ns × (0.99,1.01)     142ns × (1.00,1.00)  ~ (p=0.178)
    BenchmarkRegexpMatchEasy0_1K       408ns × (1.00,1.00)     392ns × (0.99,1.00)  -3.83% (p=0.000)
    BenchmarkRegexpMatchEasy1_32       122ns × (1.00,1.00)     122ns × (1.00,1.00)  ~ (p=0.178)
    BenchmarkRegexpMatchEasy1_1K       626ns × (1.00,1.01)     624ns × (0.99,1.00)  ~ (p=0.122)
    BenchmarkRegexpMatchMedium_32      202ns × (0.99,1.00)     205ns × (0.99,1.01)  +1.58% (p=0.001)
    BenchmarkRegexpMatchMedium_1K     54.4µs × (1.00,1.00)    55.5µs × (1.00,1.00)  +1.86% (p=0.000)
    BenchmarkRegexpMatchHard_32       2.68µs × (1.00,1.00)    2.71µs × (1.00,1.00)  +0.97% (p=0.002)
    BenchmarkRegexpMatchHard_1K       79.8µs × (1.00,1.01)    80.5µs × (1.00,1.01)  +0.94% (p=0.003)
    BenchmarkRevcomp                   590ms × (0.99,1.01)     585ms × (1.00,1.00)  ~ (p=0.066)
    BenchmarkTemplate                  111ms × (0.97,1.02)     112ms × (0.99,1.01)  ~ (p=0.201)
    BenchmarkTimeParse                 392ns × (1.00,1.00)     385ns × (1.00,1.00)  -1.69% (p=0.000)
    BenchmarkTimeFormat                449ns × (0.98,1.01)     448ns × (0.99,1.01)  ~ (p=0.550)
    
    Change-Id: Ie7c3830c481d96c9043e7bf26853c6c1d05dc9f4
    Reviewed-on: https://go-review.googlesource.com/9364Reviewed-by: 's avatarRick Hudson <rlh@golang.org>
    63caec5d
mheap.go 29.7 KB