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sync/channels: provide `try_push(), try_pop() as public methods (#6101)

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Uwe Krüger 2020-08-10 18:06:42 +02:00 committed by GitHub
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commit c3cdfa1c96
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6 changed files with 82 additions and 17 deletions
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2
doc/upcoming.md
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@ -252,7 +252,7 @@ if ch.pop(&m) {
The select call is somewhat tricky. The `channel_select()` function needs three arrays that
contain the channels, the directions (pop/push) and the object references and
a timeout of type `time.Duration` (or `0` to wait unlimited) as parameters. It returns the
a timeout of type `time.Duration` (`time.infinite` or `-1` to wait unlimited) as parameters. It returns the
index of the object that was pushed or popped or `-1` for timeout.
```v

39
vlib/sync/bench/results.md Normal file
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@ -0,0 +1,39 @@
# Channel Benchmark Results
This documents lists several benchmark results for different platforms in order to
identify performance regressions and improvements.
The are measured using the command
```
> channel_bench_* <nsend> <nrec> <buflen> <nobj>
nsend ... number of threads that push objects into the channel
nrec .... number of threads that pop objects from the channel
buflen .. length of channel buffer queue - `0` means unbuffered channel
nobj .... number of objects to pass thru the channel
```
## AMD Ryzen 7 3800X, Ubuntu-20.04 x86_64
10000000 Objects transfered, results in Objects/µs
| nsend | nrec | buflen | **V (gcc -O2)** | **V (tcc)** | **Go (glang)** | **Go (gccgo -O2)** |
| :---: | :---:| :---: | :---: | :---: | :---: | :---: |
| 1 | 1 | 0 | 0.95 | 0.66 | 4.65 | 0.56 |
| 1 | 1 | 100 | 3.26 | 2.24 | 18.90 | 6.08 |
| 4 | 4 | 0 | 0.25 | 0.24 | 1.84 | 0.84 |
| 4 | 4 | 100 | 2.78 | 2.63 | 7.43 | 3.71 |
## Raspberry Pi 3B+, Void Linux musl 32 bit
10000000 Objects transfered, results in Objects/µs
| nsend | nrec | buflen | **V (gcc -O2)** | **Go (glang)** |
| :---: | :---:| :---: | :---: | :---: |
| 1 | 1 | 0 | 0.37 | 0.21 |
| 1 | 1 | 100 | 1.03 | 0.74 |
| 4 | 4 | 0 | 0.04 | 0.38 |
| 4 | 4 | 100 | 2.78 | 2.63 |
| 2 | 2 | 0 | 0.05 | 0.38 |
| 2 | 2 | 100 | 1.26 | 0.75 |

2
vlib/sync/channel_select_test.v
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@ -48,7 +48,7 @@ fn test_select() {
mut sl := i64(0)
mut objs := [voidptr(&ri), &sl, &rl, &rb]
for _ in 0 .. 1200 {
idx := sync.channel_select(mut channels, directions, mut objs, 0)
idx := sync.channel_select(mut channels, directions, mut objs, -1)
match idx {
0 {
sum += ri

46
vlib/sync/channels.v
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@ -152,17 +152,26 @@ pub fn (mut ch Channel) close() {
C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
}
[inline]
pub fn (mut ch Channel) push(src voidptr) {
if ch.try_push(src, false) == .closed {
if ch.try_push_priv(src, false) == .closed {
panic('push on closed channel')
}
}
fn (mut ch Channel) try_push(src voidptr, no_block bool) TransactionState {
[inline]
pub fn (mut ch Channel) try_push(src voidptr) TransactionState {
return ch.try_push_priv(src, false)
}
fn (mut ch Channel) try_push_priv(src voidptr, no_block bool) TransactionState {
if C.atomic_load_u16(&ch.closed) != 0 {
return .closed
}
spinloops_, spinloops_sem_ := if no_block { 1, 1 } else { spinloops, spinloops_sem }
mut spinloops_sem_, spinloops_ := if no_block { spinloops, spinloops_sem } else { 1, 1 }
$if macos {
spinloops_sem_ = 1
}
mut have_swapped := false
for {
mut got_sem := false
@ -307,12 +316,21 @@ fn (mut ch Channel) try_push(src voidptr, no_block bool) TransactionState {
}
}
[inline]
pub fn (mut ch Channel) pop(dest voidptr) bool {
return ch.try_pop(dest, false) == .success
return ch.try_pop_priv(dest, false) == .success
}
fn (mut ch Channel) try_pop(dest voidptr, no_block bool) TransactionState {
spinloops_, spinloops_sem_ := if no_block { 1, 1 } else { spinloops, spinloops_sem }
[inline]
pub fn (mut ch Channel) try_pop(dest voidptr) TransactionState {
return ch.try_pop_priv(dest, false)
}
fn (mut ch Channel) try_pop_priv(dest voidptr, no_block bool) TransactionState {
mut spinloops_sem_, spinloops_ := if no_block { spinloops, spinloops_sem } else { 1, 1 }
$if macos {
spinloops_sem_ = 1
}
mut have_swapped := false
mut write_in_progress := false
for {
@ -465,7 +483,11 @@ fn (mut ch Channel) try_pop(dest voidptr, no_block bool) TransactionState {
}
// Wait `timeout` on any of `channels[i]` until one of them can push (`is_push[i] = true`) or pop (`is_push[i] = false`)
// object referenced by `objrefs[i]`. `timeout = 0` means wait unlimited time
// object referenced by `objrefs[i]`. `timeout < 0` means wait unlimited time. `timeout == 0` means return immediately
// if no transaction can be performed without waiting.
// return value: the index of the channel on which a transaction has taken place
// -1 if waiting for a transaction has exceeded timeout
// -2 if all channels are closed
pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []voidptr, timeout time.Duration) int {
assert channels.len == dir.len
@ -499,7 +521,7 @@ pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []vo
C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
}
}
stopwatch := if timeout == 0 { time.StopWatch{} } else { time.new_stopwatch({}) }
stopwatch := if timeout <= 0 { time.StopWatch{} } else { time.new_stopwatch({}) }
mut event_idx := -1 // negative index means `timed out`
for {
rnd := rand.u32_in_range(0, u32(channels.len))
@ -510,7 +532,7 @@ pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []vo
i -= channels.len
}
if dir[i] == .push {
stat := channels[i].try_push(objrefs[i], true)
stat := channels[i].try_push_priv(objrefs[i], true)
if stat == .success {
event_idx = i
goto restore
@ -518,7 +540,7 @@ pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []vo
num_closed++
}
} else {
stat := channels[i].try_pop(objrefs[i], true)
stat := channels[i].try_pop_priv(objrefs[i], true)
if stat == .success {
event_idx = i
goto restore
@ -531,7 +553,9 @@ pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []vo
event_idx = -2
goto restore
}
if timeout > 0 {
if timeout == 0 {
goto restore
} else if timeout > 0 {
remaining := timeout - stopwatch.elapsed()
if !sem.timed_wait(remaining) {
goto restore

3
vlib/sync/select_close_test.v
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@ -1,4 +1,5 @@
import sync
import time
fn do_rec_i64(mut ch sync.Channel) {
mut sum := i64(0)
@ -55,7 +56,7 @@ fn test_select() {
mut sl := i64(0)
mut objs := [voidptr(&ri), &sl, &rl, &rb]
for j in 0 .. 1101 {
idx := sync.channel_select(mut channels, directions, mut objs, 0)
idx := sync.channel_select(mut channels, directions, mut objs, time.infinite)
match idx {
0 {
sum += ri

7
vlib/time/time.v
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@ -363,9 +363,10 @@ pub const(
nanosecond = Duration(1)
microsecond = Duration(1000) * nanosecond
millisecond = Duration(1000) * microsecond
second = Duration(1000) * millisecond
minute = Duration(60) * second
hour = Duration(60) * minute
second = Duration(1000) * millisecond
minute = Duration(60) * second
hour = Duration(60) * minute
infinite = Duration(-1)
)
// nanoseconds returns the duration as an integer number of nanoseconds.