MTLSharedEvent for synchronization take 2

[christiangnrd]

Not ready to merge as I haven't changed anything since #645 but leaving it up.

I'm considering maybe making it an experimental local preference that's off by default and then adding a special CI to try and catch failures.

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diff --git a/lib/mtl/capture.jl b/lib/mtl/capture.jl
index 7d28793f..9f29bdd3 100644
--- a/lib/mtl/capture.jl
+++ b/lib/mtl/capture.jl
@@ -12,13 +12,13 @@ Use [`beginScope()`](@ref) and [`endScope()`](@ref) to set the boundaries for a
 """
 MTLCaptureScope
 
-function MTLCaptureScope(queue::MTLDevice, manager=MTLCaptureManager())
+function MTLCaptureScope(queue::MTLDevice, manager = MTLCaptureManager())
     handle = @objc [manager::id{MTLCaptureManager} newCaptureScopeWithDevice:queue::id{MTLDevice}]::id{MTLCaptureScope}
-    MTLCaptureScope(handle)
+    return MTLCaptureScope(handle)
 end
-function MTLCaptureScope(queue::MTLCommandQueue, manager=MTLCaptureManager())
+function MTLCaptureScope(queue::MTLCommandQueue, manager = MTLCaptureManager())
     handle = @objc [manager::id{MTLCaptureManager} newCaptureScopeWithCommandQueue:queue::id{MTLCommandQueue}]::id{MTLCaptureScope}
-    MTLCaptureScope(handle)
+    return MTLCaptureScope(handle)
 end
 
 # @objcwrapper MTLCaptureScope <: NSObject
@@ -68,7 +68,8 @@ function MTLCaptureDescriptor()
 end
 
 # TODO: Add capture state
-function MTLCaptureDescriptor(obj::Union{MTLDevice, MTLCommandQueue, MTLCaptureScope},
+function MTLCaptureDescriptor(
+        obj::Union{MTLDevice, MTLCommandQueue, MTLCaptureScope},
                               destination::MTLCaptureDestination;
                               folder::String=nothing)
     desc = MTLCaptureDescriptor()
@@ -119,7 +120,8 @@ end
 
 Start GPU frame capture using the default capture object and specifying capture descriptor parameters directly.
 """
-function startCapture(obj::Union{MTLDevice, MTLCommandQueue, MTLCaptureScope},
+function startCapture(
+        obj::Union{MTLDevice, MTLCommandQueue, MTLCaptureScope},
                       destination::MTLCaptureDestination=MTLCaptureDestinationGPUTraceDocument;
                       folder::String=nothing)
     if destination == MTLCaptureDestinationGPUTraceDocument && folder === nothing
diff --git a/lib/mtl/events.jl b/lib/mtl/events.jl
index 374f4285..8d2345ed 100644
--- a/lib/mtl/events.jl
+++ b/lib/mtl/events.jl
@@ -29,9 +29,11 @@ function MTLSharedEvent(dev::MTLDevice)
     return obj
 end
 
-function waitUntilSignaledValue(ev::MTLSharedEvent, value, timeoutMS=typemax(UInt64))
-    @objc [ev::id{MTLSharedEvent} waitUntilSignaledValue:value::UInt64
-                        timeoutMS:timeoutMS::UInt64]::Bool
+function waitUntilSignaledValue(ev::MTLSharedEvent, value, timeoutMS = typemax(UInt64))
+    return @objc [
+        ev::id{MTLSharedEvent} waitUntilSignaledValue:value::UInt64
+        timeoutMS:timeoutMS::UInt64
+    ]::Bool
 end
 
 ## shared event handle
diff --git a/src/state.jl b/src/state.jl
index ffa5f53d..918731c4 100644
--- a/src/state.jl
+++ b/src/state.jl
@@ -61,7 +61,7 @@ end
 Return the `MTLSharedEvent` used to synchronize a queue
 """
 function queue_event(queue::MTLCommandQueue)
-    get!(task_local_storage(), (:MTLSharedEvent, queue)) do
+    return get!(task_local_storage(), (:MTLSharedEvent, queue)) do
         MTLSharedEvent(queue.device)
     end::MTLSharedEvent
 end
diff --git a/test/capturing.jl b/test/capturing.jl
index 9b1da7f5..7dee3cae 100644
--- a/test/capturing.jl
+++ b/test/capturing.jl
@@ -36,9 +36,9 @@ desc.captureObject = dev
 desc.destination = MTL.MTLCaptureDestinationGPUTraceDocument
 @test desc.destination == MTL.MTLCaptureDestinationGPUTraceDocument
 
-# Capture Manager supports destination
-@test !supports_destination(manager, MTL.MTLCaptureDestinationDeveloperTools)
-@test supports_destination(manager, MTL.MTLCaptureDestinationGPUTraceDocument)
+            # Capture Manager supports destination
+            @test !supports_destination(manager, MTL.MTLCaptureDestinationDeveloperTools)
+            @test supports_destination(manager, MTL.MTLCaptureDestinationGPUTraceDocument)
 
 # Output URL
 @test desc.outputURL === nothing
@@ -69,7 +69,7 @@ bufferA = MtlArray{Float32,1,SharedStorage}(undef, tuple(4))
 @test manager.isCapturing == false
 startCapture(manager, desc)
 @test manager.isCapturing
-@test_throws "Capture manager is already capturing." startCapture(manager, desc)
+            @test_throws "Capture manager is already capturing." startCapture(manager, desc)
 Metal.@sync @metal threads=4 tester(bufferA)
 stopCapture(manager)
 @test manager.isCapturing == false

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Metal Benchmarks

Details

Benchmark suite	Current: 04e52b9	Previous: 822abde	Ratio
latency/precompile	25029149041 ns	24961495792 ns	1.00
latency/ttfp	2129357833 ns	2126570334 ns	1.00
latency/import	1223676125 ns	1221863250 ns	1.00
integration/metaldevrt	836250 ns	920646 ns	0.91
integration/byval/slices=1	1544333 ns	1636875 ns	0.94
integration/byval/slices=3	9111916 ns	8533229 ns	1.07
integration/byval/reference	1533291.5 ns	1625125 ns	0.94
integration/byval/slices=2	2568958 ns	2708917 ns	0.95
kernel/indexing	568167 ns	674520.5 ns	0.84
kernel/indexing_checked	572750 ns	692979.5 ns	0.83
kernel/launch	12084 ns	12292 ns	0.98
kernel/rand	552417 ns	623458 ns	0.89
array/construct	6291 ns	6250 ns	1.01
array/broadcast	593666.5 ns	667000 ns	0.89
array/random/randn/Float32	794125 ns	822375 ns	0.97
array/random/randn!/Float32	605666.5 ns	627417 ns	0.97
array/random/rand!/Int64	549958 ns	555042 ns	0.99
array/random/rand!/Float32	464000 ns	588291 ns	0.79
array/random/rand/Int64	774208 ns	806208 ns	0.96
array/random/rand/Float32	645208 ns	649083 ns	0.99
array/accumulate/Int64/1d	1255834 ns	1351708 ns	0.93
array/accumulate/Int64/dims=1	1815625 ns	1895167 ns	0.96
array/accumulate/Int64/dims=2	2141166.5 ns	2224583 ns	0.96
array/accumulate/Int64/dims=1L	11691792 ns	11807458 ns	0.99
array/accumulate/Int64/dims=2L	9648791.5 ns	9845792 ns	0.98
array/accumulate/Float32/1d	1100917 ns	1211020.5 ns	0.91
array/accumulate/Float32/dims=1	1542875 ns	1623125 ns	0.95
array/accumulate/Float32/dims=2	1858625 ns	1913375 ns	0.97
array/accumulate/Float32/dims=1L	9777021 ns	10039875 ns	0.97
array/accumulate/Float32/dims=2L	7226166 ns	7298229.5 ns	0.99
array/reductions/reduce/Int64/1d	1280729.5 ns	1341854 ns	0.95
array/reductions/reduce/Int64/dims=1	1078083 ns	1141520.5 ns	0.94
array/reductions/reduce/Int64/dims=2	1176666 ns	1277145.5 ns	0.92
array/reductions/reduce/Int64/dims=1L	2020708 ns	2034687.5 ns	0.99
array/reductions/reduce/Int64/dims=2L	3404792 ns	3549500 ns	0.96
array/reductions/reduce/Float32/1d	964958 ns	1067125 ns	0.90
array/reductions/reduce/Float32/dims=1	815000 ns	883229.5 ns	0.92
array/reductions/reduce/Float32/dims=2	751083 ns	810979.5 ns	0.93
array/reductions/reduce/Float32/dims=1L	1330021 ns	1373208.5 ns	0.97
array/reductions/reduce/Float32/dims=2L	1755500 ns	1888250 ns	0.93
array/reductions/mapreduce/Int64/1d	1310875 ns	1375438 ns	0.95
array/reductions/mapreduce/Int64/dims=1	1079792 ns	1176500 ns	0.92
array/reductions/mapreduce/Int64/dims=2	1189562 ns	1285062.5 ns	0.93
array/reductions/mapreduce/Int64/dims=1L	1904562.5 ns	2087041 ns	0.91
array/reductions/mapreduce/Int64/dims=2L	3304000 ns	3445167 ns	0.96
array/reductions/mapreduce/Float32/1d	985334 ns	1065917 ns	0.92
array/reductions/mapreduce/Float32/dims=1	802875 ns	892125 ns	0.90
array/reductions/mapreduce/Float32/dims=2	758625 ns	809583 ns	0.94
array/reductions/mapreduce/Float32/dims=1L	1331812.5 ns	1359000 ns	0.98
array/reductions/mapreduce/Float32/dims=2L	1775792 ns	1898271 ns	0.94
array/private/copyto!/gpu_to_gpu	634333 ns	654166 ns	0.97
array/private/copyto!/cpu_to_gpu	802708 ns	826625 ns	0.97
array/private/copyto!/gpu_to_cpu	784458 ns	813104.5 ns	0.96
array/private/iteration/findall/int	1571125 ns	1668417 ns	0.94
array/private/iteration/findall/bool	1425333.5 ns	1504500 ns	0.95
array/private/iteration/findfirst/int	1800541.5 ns	1934521 ns	0.93
array/private/iteration/findfirst/bool	1652708 ns	1855687 ns	0.89
array/private/iteration/scalar	4217125 ns	4774709 ns	0.88
array/private/iteration/logical	2525375 ns	2574750 ns	0.98
array/private/iteration/findmin/1d	1875812.5 ns	2064500 ns	0.91
array/private/iteration/findmin/2d	1518667 ns	1624500 ns	0.93
array/private/copy	568292 ns	550458 ns	1.03
array/shared/copyto!/gpu_to_gpu	85125 ns	83333 ns	1.02
array/shared/copyto!/cpu_to_gpu	82459 ns	94500 ns	0.87
array/shared/copyto!/gpu_to_cpu	82167 ns	82958 ns	0.99
array/shared/iteration/findall/int	1576021 ns	1643125 ns	0.96
array/shared/iteration/findall/bool	1426479 ns	1516125 ns	0.94
array/shared/iteration/findfirst/int	1325084 ns	1457083 ns	0.91
array/shared/iteration/findfirst/bool	1308916.5 ns	1419167 ns	0.92
array/shared/iteration/scalar	210584 ns	159229.5 ns	1.32
array/shared/iteration/logical	2399542 ns	2361416 ns	1.02
array/shared/iteration/findmin/1d	1392937.5 ns	1620625 ns	0.86
array/shared/iteration/findmin/2d	1518708 ns	1622208 ns	0.94
array/shared/copy	253458.5 ns	245750 ns	1.03
array/permutedims/4d	2343333.5 ns	2439396 ns	0.96
array/permutedims/2d	1146875 ns	1226959 ns	0.93
array/permutedims/3d	1666333.5 ns	1746270.5 ns	0.95
metal/synchronization/stream	18833 ns	14833 ns	1.27
metal/synchronization/context	20042 ns	15334 ns	1.31

This comment was automatically generated by workflow using github-action-benchmark.

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Codecov Report

❌ Patch coverage is 96.15385% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.20%. Comparing base (822abde) to head (04e52b9).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/state.jl	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #690      +/-   ##
==========================================
+ Coverage   80.89%   81.20%   +0.31%     
==========================================
  Files          62       62              
  Lines        2790     2810      +20     
==========================================
+ Hits         2257     2282      +25     
+ Misses        533      528       -5     

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[christiangnrd]

I suspect stopCapture isn't quite synchronous, and that sometimes the command buffer isn't fully finished by the time manager.isCaptured is checked if it's called right after waitUntilSignaledValue returns.

The current spinlock is a potential option. Another is maybe ensuring we synchronize after stopCapture (in the macro and I would add that to the test).

@maleadt any thoughts?

[maleadt]

Another is maybe ensuring we synchronize after stopCapture (in the macro and I would add that to the test).

Seems like the cleaner solution, no?

[christiangnrd]

Unfortunately synchronizing doesn't work. With 14d3d0e locally, when it fails, it usually takes ~90 ms for capture to stop. Should I just use a spinlock?

[maleadt]

Yeah, that seems reasonable. Do add some code comments about the reason though.