Hi,
I've written a small library (https://github.com/toefel18/go-patan) in that
stores counters and collects statistics (running
min/max/average/stddeviation) of a program during runtime. There is a lock
based implementation and a channel based implementation. I've written this
library before in Java as well https://github.com/toefel18/patan. The Java
version with equivalent implementation is much faster than both the channel
and locking implementations in Go, I really don't understand why.
This program has a store that holds the data, and a sync.Mutex that guards
concurrent access on reads and writes. This is a snippet of the locking
based implementation:
type Store struct {
durations map[string]*Distribution
counters map[string]int64
samples map[string]*Distribution
lock *sync.Mutex
}
func (store *Store) addSample(key string, value int64) {
store.addToStore(store.samples, key, value)
}
func (store *Store) addDuration(key string, value int64) {
store.addToStore(store.durations, key, value)
}
func (store *Store) addToStore(destination map[string]*Distribution, key
string, value int64) {
store.lock.Lock()
defer store.lock.Unlock()
distribution, exists := destination[key]
if !exists {
distribution = NewDistribution()
destination[key] = distribution
}
distribution.addSample(value)
}
Now, when I benchmark this GO code, I get the following results (see gist:
benchmark code
<https://gist.github.com/toefel18/96edac8f57f9ad8a4f9a86d83e726aec>):
10 threads with 20000 items took 133 millis
100 threads with 20000 items took 1809 millis
1000 threads with 20000 items took 17576 millis
10 threads with 200000 items took 1228 millis
100 threads with 200000 items took 17900 millis
When I benchmark the Java code, there are much better results (see gist: java
benchmark code
<https://gist.github.com/toefel18/9def55a8c3c53c79a4488c29c66f31e5>)
10 threads with 20000 items takes 89 millis
100 threads with 20000 items takes 265 millis
1000 threads with 20000 items takes 2888 millis
10 threads with 200000 items takes 311 millis
100 threads with 200000 items takes 3067 millis
I have profiled the Go code and created a call graph
<https://gist.githubusercontent.com/toefel18/96edac8f57f9ad8a4f9a86d83e726aec/raw/c1ff6452abaefe49c3c688b3d07e4574cbe77264/call-graph.png>.
I interpret this as follows:
GO spends 0.31 and 0.25 seconds in my methods, and pretty much the rest in
sync.(*Mutex).Lock() and sync.(*Mutex).Unlock()
The top20 output of the profiler:
(pprof) top20
59110ms of 73890ms total (80.00%)
Dropped 22 nodes (cum <= 369.45ms)
Showing top 20 nodes out of 65 (cum >= 50220ms)
flat flat% sum% cum cum%
8900ms 12.04% 12.04% 8900ms 12.04% runtime.futex
7270ms 9.84% 21.88% 7270ms 9.84% runtime/internal/atomic.Xchg
7020ms 9.50% 31.38% 7020ms 9.50% runtime.procyield
4560ms 6.17% 37.56% 4560ms 6.17% sync/atomic.CompareAndSwapUint32
4400ms 5.95% 43.51% 4400ms 5.95% runtime/internal/atomic.Xadd
4210ms 5.70% 49.21% 22040ms 29.83% runtime.lock
3650ms 4.94% 54.15% 3650ms 4.94% runtime/internal/atomic.Cas
3260ms 4.41% 58.56% 3260ms 4.41% runtime/internal/atomic.Load
2220ms 3.00% 61.56% 22810ms 30.87% sync.(*Mutex).Lock
1870ms 2.53% 64.10% 1870ms 2.53% runtime.osyield
1540ms 2.08% 66.18% 16740ms 22.66% runtime.findrunnable
1430ms 1.94% 68.11% 1430ms 1.94% runtime.freedefer
1400ms 1.89% 70.01% 1400ms 1.89% sync/atomic.AddUint32
1250ms 1.69% 71.70% 1250ms 1.69%
github.com/toefel18/go-patan/statistics/lockbased.(*Distribution).addSample
1240ms 1.68% 73.38% 3140ms 4.25% runtime.deferreturn
1070ms 1.45% 74.83% 6520ms 8.82% runtime.systemstack
1010ms 1.37% 76.19% 1010ms 1.37% runtime.newdefer
1000ms 1.35% 77.55% 1000ms 1.35% runtime.mapaccess1_faststr
950ms 1.29% 78.83% 15660ms 21.19% runtime.semacquire
860ms 1.16% 80.00% 50220ms 67.97% main.Benchmrk.func1
I would really like to understand why Locking in Go is so much slower than in
Java. I've initially written this program using channels, but that was much
slower than locking. Can somebody please help me out?
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
