go /
sync /
a60ad46e0ed33d02e09bda439efaf9c9727dbc6c syncmap: remove blocking for all operations on existing keys
In the previous version, Loads of keys with unchanged values would
block on the Mutex if the map was dirty, leading to potentially long
stalls while the read-only map is being copied to the dirty map.
This change adds a double pointer indirection to each entry and an
extra atomic load on the fast path. In exchange, it removes the need
to lock the map for nearly all operations on existing keys.
Each entry is represented by an atomically-updated pointer to an
interface{} value. The same entries are stored in both the read-only
and dirty maps. Keys deleted before the dirty map was last copied are
marked as "expunged" and omitted from the dirty map until the next
Store to that key.
Newly-stored values exist only in the dirty map. The existence of new
keys in the dirty map is indicated by an "amended" bit attached to the
read-only map, allowing Load or Delete calls for nonexistent keys to
sometimes return immediately (without acquiring the Mutex).
This trades off a bit of steady-state throughput in the "mostly hits"
case in exchange for less contention (and lower Load tail latencies)
for mixed Load/Store/Delete usage.
Unfortunately, the latency impact is currently difficult to measure
(#19128).
updates golang/go#19128
updates golang/go#18177
https://perf.golang.org/search?q=upload:20170315.5
name old time/op new time/op delta
LoadMostlyHits/*syncmap_test.DeepCopyMap 70.3ns ± 6% 70.2ns ± 4% ~ (p=0.886 n=4+4)
LoadMostlyHits/*syncmap_test.DeepCopyMap-48 10.9ns ± 4% 13.6ns ±24% ~ (p=0.314 n=4+4)
LoadMostlyHits/*syncmap_test.RWMutexMap 86.0ns ± 9% 86.0ns ± 4% ~ (p=1.000 n=4+4)
LoadMostlyHits/*syncmap_test.RWMutexMap-48 140ns ± 3% 139ns ± 2% ~ (p=0.686 n=4+4)
LoadMostlyHits/*syncmap.Map 70.6ns ± 8% 70.3ns ± 1% ~ (p=0.571 n=4+4)
LoadMostlyHits/*syncmap.Map-48 10.3ns ± 7% 11.2ns ± 5% ~ (p=0.114 n=4+4)
LoadMostlyMisses/*syncmap_test.DeepCopyMap 59.4ns ± 4% 59.4ns ± 4% ~ (p=1.000 n=4+4)
LoadMostlyMisses/*syncmap_test.DeepCopyMap-48 10.4ns ±30% 12.6ns ±29% ~ (p=0.486 n=4+4)
LoadMostlyMisses/*syncmap_test.RWMutexMap 64.8ns ± 6% 63.8ns ± 4% ~ (p=0.686 n=4+4)
LoadMostlyMisses/*syncmap_test.RWMutexMap-48 138ns ± 3% 139ns ± 2% ~ (p=0.800 n=4+4)
LoadMostlyMisses/*syncmap.Map 51.5ns ± 7% 50.4ns ± 2% ~ (p=0.371 n=4+4)
LoadMostlyMisses/*syncmap.Map-48 9.37ns ± 3% 9.40ns ± 3% ~ (p=0.886 n=4+4)
LoadOrStoreBalanced/*syncmap_test.RWMutexMap 820ns ±17% 834ns ±14% ~ (p=1.000 n=4+4)
LoadOrStoreBalanced/*syncmap_test.RWMutexMap-48 1.38µs ± 4% 1.38µs ± 3% ~ (p=0.886 n=4+4)
LoadOrStoreBalanced/*syncmap.Map 709ns ±13% 1085ns ± 9% +53.09% (p=0.029 n=4+4)
LoadOrStoreBalanced/*syncmap.Map-48 1.30µs ±13% 1.08µs ± 8% -17.40% (p=0.029 n=4+4)
LoadOrStoreUnique/*syncmap_test.RWMutexMap 1.26µs ±14% 1.16µs ±29% ~ (p=0.343 n=4+4)
LoadOrStoreUnique/*syncmap_test.RWMutexMap-48 1.82µs ±15% 1.98µs ± 6% ~ (p=0.143 n=4+4)
LoadOrStoreUnique/*syncmap.Map 1.06µs ± 7% 1.86µs ±11% +76.09% (p=0.029 n=4+4)
LoadOrStoreUnique/*syncmap.Map-48 2.00µs ± 4% 1.62µs ± 4% -19.20% (p=0.029 n=4+4)
LoadOrStoreCollision/*syncmap_test.DeepCopyMap 32.9ns ± 8% 32.6ns ± 9% ~ (p=0.686 n=4+4)
LoadOrStoreCollision/*syncmap_test.DeepCopyMap-48 2.26ns ±136% 3.41ns ±62% ~ (p=0.114 n=4+4)
LoadOrStoreCollision/*syncmap_test.RWMutexMap 58.0ns ±20% 54.6ns ±17% ~ (p=0.343 n=4+4)
LoadOrStoreCollision/*syncmap_test.RWMutexMap-48 458ns ± 2% 445ns ± 6% ~ (p=0.229 n=4+4)
LoadOrStoreCollision/*syncmap.Map 35.8ns ± 5% 39.6ns ± 9% ~ (p=0.114 n=4+4)
LoadOrStoreCollision/*syncmap.Map-48 1.24ns ± 2% 1.58ns ± 4% +27.16% (p=0.029 n=4+4)
Range/*syncmap_test.DeepCopyMap 19.7µs ± 4% 19.8µs ± 3% ~ (p=0.686 n=4+4)
Range/*syncmap_test.DeepCopyMap-48 763ns ± 1% 864ns ± 3% +13.24% (p=0.029 n=4+4)
Range/*syncmap_test.RWMutexMap 20.9µs ± 3% 20.4µs ± 4% ~ (p=0.343 n=4+4)
Range/*syncmap_test.RWMutexMap-48 764ns ± 1% 870ns ± 1% +13.77% (p=0.029 n=4+4)
Range/*syncmap.Map 20.4µs ± 5% 22.7µs ± 5% +10.98% (p=0.029 n=4+4)
Range/*syncmap.Map-48 776ns ± 3% 954ns ± 4% +22.95% (p=0.029 n=4+4)
AdversarialAlloc/*syncmap_test.DeepCopyMap 206ns ± 5% 199ns ± 2% ~ (p=0.200 n=4+4)
AdversarialAlloc/*syncmap_test.DeepCopyMap-48 8.94µs ± 5% 9.21µs ± 4% ~ (p=0.200 n=4+4)
AdversarialAlloc/*syncmap_test.RWMutexMap 63.4ns ± 4% 63.8ns ± 3% ~ (p=0.686 n=4+4)
AdversarialAlloc/*syncmap_test.RWMutexMap-48 184ns ±10% 198ns ±11% ~ (p=0.343 n=4+4)
AdversarialAlloc/*syncmap.Map 213ns ± 3% 264ns ± 3% +23.97% (p=0.029 n=4+4)
AdversarialAlloc/*syncmap.Map-48 556ns ± 5% 1389ns ± 8% +149.93% (p=0.029 n=4+4)
AdversarialDelete/*syncmap_test.DeepCopyMap 300ns ± 6% 304ns ± 7% ~ (p=0.886 n=4+4)
AdversarialDelete/*syncmap_test.DeepCopyMap-48 647ns ± 3% 646ns ± 3% ~ (p=0.943 n=4+4)
AdversarialDelete/*syncmap_test.RWMutexMap 69.1ns ± 1% 69.2ns ± 6% ~ (p=0.686 n=4+4)
AdversarialDelete/*syncmap_test.RWMutexMap-48 289ns ±15% 300ns ±17% ~ (p=0.829 n=4+4)
AdversarialDelete/*syncmap.Map 198ns ± 5% 264ns ± 2% +33.17% (p=0.029 n=4+4)
AdversarialDelete/*syncmap.Map-48 291ns ± 9% 173ns ± 8% -40.50% (p=0.029 n=4+4)
name old alloc/op new alloc/op delta
LoadMostlyHits/*syncmap_test.DeepCopyMap 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyHits/*syncmap_test.DeepCopyMap-48 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyHits/*syncmap_test.RWMutexMap 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyHits/*syncmap_test.RWMutexMap-48 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyHits/*syncmap.Map 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyHits/*syncmap.Map-48 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyMisses/*syncmap_test.DeepCopyMap 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyMisses/*syncmap_test.DeepCopyMap-48 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyMisses/*syncmap_test.RWMutexMap 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyMisses/*syncmap_test.RWMutexMap-48 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyMisses/*syncmap.Map 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadMostlyMisses/*syncmap.Map-48 7.00B ± 0% 7.00B ± 0% ~ (all equal)
LoadOrStoreBalanced/*syncmap_test.RWMutexMap 95.0B ± 0% 95.0B ± 0% ~ (all equal)
LoadOrStoreBalanced/*syncmap_test.RWMutexMap-48 95.0B ± 0% 95.0B ± 0% ~ (all equal)
LoadOrStoreBalanced/*syncmap.Map 95.0B ± 0% 88.0B ± 0% -7.37% (p=0.029 n=4+4)
LoadOrStoreBalanced/*syncmap.Map-48 95.0B ± 0% 88.0B ± 0% -7.37% (p=0.029 n=4+4)
LoadOrStoreUnique/*syncmap_test.RWMutexMap 175B ± 0% 175B ± 0% ~ (all equal)
LoadOrStoreUnique/*syncmap_test.RWMutexMap-48 175B ± 0% 175B ± 0% ~ (all equal)
LoadOrStoreUnique/*syncmap.Map 175B ± 0% 161B ± 0% -8.00% (p=0.029 n=4+4)
LoadOrStoreUnique/*syncmap.Map-48 175B ± 0% 161B ± 0% -8.00% (p=0.029 n=4+4)
LoadOrStoreCollision/*syncmap_test.DeepCopyMap 0.00B 0.00B ~ (all equal)
LoadOrStoreCollision/*syncmap_test.DeepCopyMap-48 0.00B 0.00B ~ (all equal)
LoadOrStoreCollision/*syncmap_test.RWMutexMap 0.00B 0.00B ~ (all equal)
LoadOrStoreCollision/*syncmap_test.RWMutexMap-48 0.00B 0.00B ~ (all equal)
LoadOrStoreCollision/*syncmap.Map 0.00B 0.00B ~ (all equal)
LoadOrStoreCollision/*syncmap.Map-48 0.00B 0.00B ~ (all equal)
Range/*syncmap_test.DeepCopyMap 0.00B 0.00B ~ (all equal)
Range/*syncmap_test.DeepCopyMap-48 0.00B 0.00B ~ (all equal)
Range/*syncmap_test.RWMutexMap 0.00B 0.00B ~ (all equal)
Range/*syncmap_test.RWMutexMap-48 0.00B 0.00B ~ (all equal)
Range/*syncmap.Map 0.00B 0.00B ~ (all equal)
Range/*syncmap.Map-48 0.00B 0.00B ~ (all equal)
AdversarialAlloc/*syncmap_test.DeepCopyMap 74.0B ± 0% 74.0B ± 0% ~ (all equal)
AdversarialAlloc/*syncmap_test.DeepCopyMap-48 3.15kB ± 0% 3.15kB ± 0% ~ (p=1.000 n=4+4)
AdversarialAlloc/*syncmap_test.RWMutexMap 8.00B ± 0% 8.00B ± 0% ~ (all equal)
AdversarialAlloc/*syncmap_test.RWMutexMap-48 8.00B ± 0% 8.00B ± 0% ~ (all equal)
AdversarialAlloc/*syncmap.Map 74.0B ± 0% 55.0B ± 0% -25.68% (p=0.029 n=4+4)
AdversarialAlloc/*syncmap.Map-48 8.00B ± 0% 56.25B ± 1% +603.12% (p=0.029 n=4+4)
AdversarialDelete/*syncmap_test.DeepCopyMap 155B ± 0% 155B ± 0% ~ (all equal)
AdversarialDelete/*syncmap_test.DeepCopyMap-48 156B ± 0% 156B ± 0% ~ (p=1.000 n=4+4)
AdversarialDelete/*syncmap_test.RWMutexMap 8.00B ± 0% 8.00B ± 0% ~ (all equal)
AdversarialDelete/*syncmap_test.RWMutexMap-48 8.00B ± 0% 8.00B ± 0% ~ (all equal)
AdversarialDelete/*syncmap.Map 81.0B ± 0% 65.0B ± 0% -19.75% (p=0.029 n=4+4)
AdversarialDelete/*syncmap.Map-48 23.0B ± 9% 15.2B ± 5% -33.70% (p=0.029 n=4+4)
name old allocs/op new allocs/op delta
LoadMostlyHits/*syncmap_test.DeepCopyMap 0.00 0.00 ~ (all equal)
LoadMostlyHits/*syncmap_test.DeepCopyMap-48 0.00 0.00 ~ (all equal)
LoadMostlyHits/*syncmap_test.RWMutexMap 0.00 0.00 ~ (all equal)
LoadMostlyHits/*syncmap_test.RWMutexMap-48 0.00 0.00 ~ (all equal)
LoadMostlyHits/*syncmap.Map 0.00 0.00 ~ (all equal)
LoadMostlyHits/*syncmap.Map-48 0.00 0.00 ~ (all equal)
LoadMostlyMisses/*syncmap_test.DeepCopyMap 0.00 0.00 ~ (all equal)
LoadMostlyMisses/*syncmap_test.DeepCopyMap-48 0.00 0.00 ~ (all equal)
LoadMostlyMisses/*syncmap_test.RWMutexMap 0.00 0.00 ~ (all equal)
LoadMostlyMisses/*syncmap_test.RWMutexMap-48 0.00 0.00 ~ (all equal)
LoadMostlyMisses/*syncmap.Map 0.00 0.00 ~ (all equal)
LoadMostlyMisses/*syncmap.Map-48 0.00 0.00 ~ (all equal)
LoadOrStoreBalanced/*syncmap_test.RWMutexMap 2.00 ± 0% 2.00 ± 0% ~ (all equal)
LoadOrStoreBalanced/*syncmap_test.RWMutexMap-48 2.00 ± 0% 2.00 ± 0% ~ (all equal)
LoadOrStoreBalanced/*syncmap.Map 2.00 ± 0% 3.00 ± 0% +50.00% (p=0.029 n=4+4)
LoadOrStoreBalanced/*syncmap.Map-48 2.00 ± 0% 3.00 ± 0% +50.00% (p=0.029 n=4+4)
LoadOrStoreUnique/*syncmap_test.RWMutexMap 2.00 ± 0% 2.00 ± 0% ~ (all equal)
LoadOrStoreUnique/*syncmap_test.RWMutexMap-48 2.00 ± 0% 2.00 ± 0% ~ (all equal)
LoadOrStoreUnique/*syncmap.Map 2.00 ± 0% 4.00 ± 0% +100.00% (p=0.029 n=4+4)
LoadOrStoreUnique/*syncmap.Map-48 2.00 ± 0% 4.00 ± 0% +100.00% (p=0.029 n=4+4)
LoadOrStoreCollision/*syncmap_test.DeepCopyMap 0.00 0.00 ~ (all equal)
LoadOrStoreCollision/*syncmap_test.DeepCopyMap-48 0.00 0.00 ~ (all equal)
LoadOrStoreCollision/*syncmap_test.RWMutexMap 0.00 0.00 ~ (all equal)
LoadOrStoreCollision/*syncmap_test.RWMutexMap-48 0.00 0.00 ~ (all equal)
LoadOrStoreCollision/*syncmap.Map 0.00 0.00 ~ (all equal)
LoadOrStoreCollision/*syncmap.Map-48 0.00 0.00 ~ (all equal)
Range/*syncmap_test.DeepCopyMap 0.00 0.00 ~ (all equal)
Range/*syncmap_test.DeepCopyMap-48 0.00 0.00 ~ (all equal)
Range/*syncmap_test.RWMutexMap 0.00 0.00 ~ (all equal)
Range/*syncmap_test.RWMutexMap-48 0.00 0.00 ~ (all equal)
Range/*syncmap.Map 0.00 0.00 ~ (all equal)
Range/*syncmap.Map-48 0.00 0.00 ~ (all equal)
AdversarialAlloc/*syncmap_test.DeepCopyMap 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialAlloc/*syncmap_test.DeepCopyMap-48 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialAlloc/*syncmap_test.RWMutexMap 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialAlloc/*syncmap_test.RWMutexMap-48 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialAlloc/*syncmap.Map 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialAlloc/*syncmap.Map-48 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialDelete/*syncmap_test.DeepCopyMap 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialDelete/*syncmap_test.DeepCopyMap-48 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialDelete/*syncmap_test.RWMutexMap 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialDelete/*syncmap_test.RWMutexMap-48 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialDelete/*syncmap.Map 1.00 ± 0% 1.00 ± 0% ~ (all equal)
AdversarialDelete/*syncmap.Map-48 1.00 ± 0% 1.00 ± 0% ~ (all equal)
Change-Id: I93c9458505d84238cc8e9016a7dfd285868af236
Reviewed-on: https://go-review.googlesource.com/37342
Reviewed-by: Russ Cox <rsc@golang.org>
1 file changed
