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runtime: avoid extra tophash check in mapassign when key comparison is cheap

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mapaccess and mapdelete functions are already optimized to prefer direct
key comparison instead of tophash checks when key comparison is cheap.

Extended version of golang.org/cl/55235.

AMD64:
name                old time/op    new time/op    delta
MapPopulate/1         42.5ns ± 2%    40.3ns ± 2%  -5.37%  (p=0.000 n=9+10)
MapPopulate/10         558ns ± 1%     556ns ± 1%    ~     (p=0.157 n=10+10)
MapPopulate/100       7.75µs ± 1%    7.66µs ± 2%  -1.19%  (p=0.001 n=10+10)
MapPopulate/1000      92.6µs ± 1%    92.0µs ± 1%  -0.61%  (p=0.016 n=10+8)
MapPopulate/10000      817µs ± 1%     814µs ± 1%    ~     (p=0.247 n=10+10)
MapPopulate/100000    8.02ms ± 1%    7.90ms ± 2%  -1.47%  (p=0.007 n=10+10)

Change-Id: If0eca9931379cbbd37eb753e9bcd2888d8272153
Reviewed-on: https://go-review.googlesource.com/62050
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Martin Möhrmann 2017-09-06 08:36:10 +02:00
parent 4410900a3c
commit ec0e2edd3b
1 changed files with 7 additions and 8 deletions
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15
src/runtime/hashmap_fast.go
View File

@ -373,15 +373,14 @@ again:
growWork_fast32(t, h, bucket) growWork_fast32(t, h, bucket)
} }
b := (*bmap)(unsafe.Pointer(uintptr(h.buckets) + bucket*uintptr(t.bucketsize))) b := (*bmap)(unsafe.Pointer(uintptr(h.buckets) + bucket*uintptr(t.bucketsize)))
top := tophash(hash)
var inserti *uint8 var inserti *uint8
var insertk unsafe.Pointer var insertk unsafe.Pointer
var val unsafe.Pointer var val unsafe.Pointer
for { for {
for i := uintptr(0); i < bucketCnt; i++ { for i := uintptr(0); i < bucketCnt; i++ {
if b.tophash[i] != top { if b.tophash[i] == empty {
if b.tophash[i] == empty && inserti == nil { if inserti == nil {
inserti = &b.tophash[i] inserti = &b.tophash[i]
insertk = add(unsafe.Pointer(b), dataOffset+i*4) insertk = add(unsafe.Pointer(b), dataOffset+i*4)
val = add(unsafe.Pointer(b), dataOffset+bucketCnt*4+i*uintptr(t.valuesize)) val = add(unsafe.Pointer(b), dataOffset+bucketCnt*4+i*uintptr(t.valuesize))
@ -425,7 +424,8 @@ again:
} else { } else {
*(*uint32)(insertk) = key *(*uint32)(insertk) = key
} }
*inserti = top
*inserti = tophash(hash)
h.count++ h.count++
done: done:
@ -462,15 +462,14 @@ again:
growWork_fast64(t, h, bucket) growWork_fast64(t, h, bucket)
} }
b := (*bmap)(unsafe.Pointer(uintptr(h.buckets) + bucket*uintptr(t.bucketsize))) b := (*bmap)(unsafe.Pointer(uintptr(h.buckets) + bucket*uintptr(t.bucketsize)))
top := tophash(hash)
var inserti *uint8 var inserti *uint8
var insertk unsafe.Pointer var insertk unsafe.Pointer
var val unsafe.Pointer var val unsafe.Pointer
for { for {
for i := uintptr(0); i < bucketCnt; i++ { for i := uintptr(0); i < bucketCnt; i++ {
if b.tophash[i] != top { if b.tophash[i] == empty {
if b.tophash[i] == empty && inserti == nil { if inserti == nil {
inserti = &b.tophash[i] inserti = &b.tophash[i]
insertk = add(unsafe.Pointer(b), dataOffset+i*8) insertk = add(unsafe.Pointer(b), dataOffset+i*8)
val = add(unsafe.Pointer(b), dataOffset+bucketCnt*8+i*uintptr(t.valuesize)) val = add(unsafe.Pointer(b), dataOffset+bucketCnt*8+i*uintptr(t.valuesize))
@ -521,7 +520,7 @@ again:
*(*uint64)(insertk) = key *(*uint64)(insertk) = key
} }
*inserti = top *inserti = tophash(hash)
h.count++ h.count++
done: done: