[Openmp-commits] [openmp] e876250 - [OpenMP][libomptarget] Enable parallel copies via multiple SDMA engines (#71801)
via Openmp-commits
openmp-commits at lists.llvm.org
Tue Nov 14 10:16:43 PST 2023
Author: Jan Patrick Lehr
Date: 2023-11-14T19:16:39+01:00
New Revision: e876250b636522d1eb05a908f2e1cd451feab001
URL: https://github.com/llvm/llvm-project/commit/e876250b636522d1eb05a908f2e1cd451feab001
DIFF: https://github.com/llvm/llvm-project/commit/e876250b636522d1eb05a908f2e1cd451feab001.diff
LOG: [OpenMP][libomptarget] Enable parallel copies via multiple SDMA engines (#71801)
This enables the AMDGPU plugin to use a new ROCm 5.7 interface to
dispatch asynchronous data transfers across SDMA engines.
The default functionality stays unchanged, meaning that all data
transfers are enqueued into a H2D queue or an D2H queue, depending on
transfer direction, via the HSA interface used previously.
The new interface can be enabled via the environment variable
`LIBOMPTARGET_AMDGPU_USE_MULTIPLE_SDMA_ENGINES=true` when libomptarget
is built against a recent ROCm version (5.7 and later).
As of now, requests are distributed in a round-robin fashion across
available SDMA engines.
Added:
Modified:
openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp
Removed:
################################################################################
diff --git a/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp b/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp
index a529c379844e904..5bb92f260106394 100644
--- a/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp
+++ b/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp
@@ -130,6 +130,45 @@ Error iterateAgentMemoryPools(hsa_agent_t Agent, CallbackTy Cb) {
"Error in hsa_amd_agent_iterate_memory_pools: %s");
}
+/// Dispatches an asynchronous memory copy.
+/// Enables
diff erent SDMA engines for the dispatch in a round-robin fashion.
+Error asyncMemCopy(bool UseMultipleSdmaEngines, void *Dst, hsa_agent_t DstAgent,
+ const void *Src, hsa_agent_t SrcAgent, size_t Size,
+ uint32_t NumDepSignals, const hsa_signal_t *DepSignals,
+ hsa_signal_t CompletionSignal) {
+ if (UseMultipleSdmaEngines) {
+ hsa_status_t S =
+ hsa_amd_memory_async_copy(Dst, DstAgent, Src, SrcAgent, Size,
+ NumDepSignals, DepSignals, CompletionSignal);
+ return Plugin::check(S, "Error in hsa_amd_memory_async_copy: %s");
+ }
+
+// This solution is probably not the best
+#if !(HSA_AMD_INTERFACE_VERSION_MAJOR >= 1 && \
+ HSA_AMD_INTERFACE_VERSION_MINOR >= 2)
+ return Plugin::error("Async copy on selected SDMA requires ROCm 5.7");
+#else
+ static std::atomic<int> SdmaEngine{1};
+
+ // This atomics solution is probably not the best, but should be sufficient
+ // for now.
+ // In a worst case scenario, in which threads read the same value, they will
+ // dispatch to the same SDMA engine. This may result in sub-optimal
+ // performance. However, I think the possibility to be fairly low.
+ int LocalSdmaEngine = SdmaEngine.load(std::memory_order_acquire);
+ // This call is only avail in ROCm >= 5.7
+ hsa_status_t S = hsa_amd_memory_async_copy_on_engine(
+ Dst, DstAgent, Src, SrcAgent, Size, NumDepSignals, DepSignals,
+ CompletionSignal, (hsa_amd_sdma_engine_id_t)LocalSdmaEngine,
+ /*force_copy_on_sdma=*/true);
+ // Increment to use one of three SDMA engines: 0x1, 0x2, 0x4
+ LocalSdmaEngine = (LocalSdmaEngine << 1) % 7;
+ SdmaEngine.store(LocalSdmaEngine, std::memory_order_relaxed);
+
+ return Plugin::check(S, "Error in hsa_amd_memory_async_copy_on_engine: %s");
+#endif
+}
+
} // namespace utils
/// Utility class representing generic resource references to AMDGPU resources.
@@ -945,6 +984,9 @@ struct AMDGPUStreamTy {
/// Timeout hint for HSA actively waiting for signal value to change
const uint64_t StreamBusyWaitMicroseconds;
+ /// Indicate to spread data transfers across all avilable SDMAs
+ bool UseMultipleSdmaEngines;
+
/// Return the current number of asychronous operations on the stream.
uint32_t size() const { return NextSlot; }
@@ -1170,15 +1212,15 @@ struct AMDGPUStreamTy {
InputSignal = nullptr;
// Issue the async memory copy.
- hsa_status_t Status;
if (InputSignal) {
hsa_signal_t InputSignalRaw = InputSignal->get();
- Status = hsa_amd_memory_async_copy(Dst, Agent, Src, Agent, CopySize, 1,
- &InputSignalRaw, OutputSignal->get());
- } else
- Status = hsa_amd_memory_async_copy(Dst, Agent, Src, Agent, CopySize, 0,
- nullptr, OutputSignal->get());
- return Plugin::check(Status, "Error in hsa_amd_memory_async_copy: %s");
+ return utils::asyncMemCopy(UseMultipleSdmaEngines, Dst, Agent, Src, Agent,
+ CopySize, 1, &InputSignalRaw,
+ OutputSignal->get());
+ }
+
+ return utils::asyncMemCopy(UseMultipleSdmaEngines, Dst, Agent, Src, Agent,
+ CopySize, 0, nullptr, OutputSignal->get());
}
/// Push an asynchronous memory copy device-to-host involving an unpinned
@@ -1214,21 +1256,19 @@ struct AMDGPUStreamTy {
// Issue the first step: device to host transfer. Avoid defining the input
// dependency if already satisfied.
- hsa_status_t Status;
if (InputSignal) {
hsa_signal_t InputSignalRaw = InputSignal->get();
- Status =
- hsa_amd_memory_async_copy(Inter, Agent, Src, Agent, CopySize, 1,
- &InputSignalRaw, OutputSignals[0]->get());
+ if (auto Err = utils::asyncMemCopy(
+ UseMultipleSdmaEngines, Inter, Agent, Src, Agent, CopySize, 1,
+ &InputSignalRaw, OutputSignals[0]->get()))
+ return Err;
} else {
- Status = hsa_amd_memory_async_copy(Inter, Agent, Src, Agent, CopySize, 0,
- nullptr, OutputSignals[0]->get());
+ if (auto Err = utils::asyncMemCopy(UseMultipleSdmaEngines, Inter, Agent,
+ Src, Agent, CopySize, 0, nullptr,
+ OutputSignals[0]->get()))
+ return Err;
}
- if (auto Err =
- Plugin::check(Status, "Error in hsa_amd_memory_async_copy: %s"))
- return Err;
-
// Consume another stream slot and compute dependencies.
std::tie(Curr, InputSignal) = consume(OutputSignals[1]);
assert(InputSignal && "Invalid input signal");
@@ -1242,7 +1282,7 @@ struct AMDGPUStreamTy {
std::atomic_thread_fence(std::memory_order_release);
// Issue the second step: host to host transfer.
- Status = hsa_amd_signal_async_handler(
+ hsa_status_t Status = hsa_amd_signal_async_handler(
InputSignal->get(), HSA_SIGNAL_CONDITION_EQ, 0, asyncActionCallback,
(void *)&Slots[Curr]);
@@ -1318,16 +1358,14 @@ struct AMDGPUStreamTy {
// Issue the second step: host to device transfer. Avoid defining the input
// dependency if already satisfied.
- hsa_status_t Status;
if (InputSignal && InputSignal->load()) {
hsa_signal_t InputSignalRaw = InputSignal->get();
- Status = hsa_amd_memory_async_copy(Dst, Agent, Inter, Agent, CopySize, 1,
- &InputSignalRaw, OutputSignal->get());
- } else
- Status = hsa_amd_memory_async_copy(Dst, Agent, Inter, Agent, CopySize, 0,
- nullptr, OutputSignal->get());
-
- return Plugin::check(Status, "Error in hsa_amd_memory_async_copy: %s");
+ return utils::asyncMemCopy(UseMultipleSdmaEngines, Dst, Agent, Inter,
+ Agent, CopySize, 1, &InputSignalRaw,
+ OutputSignal->get());
+ }
+ return utils::asyncMemCopy(UseMultipleSdmaEngines, Dst, Agent, Inter, Agent,
+ CopySize, 0, nullptr, OutputSignal->get());
}
// AMDGPUDeviceTy is incomplete here, passing the underlying agent instead
@@ -1353,17 +1391,15 @@ struct AMDGPUStreamTy {
// allocated by this runtime or the caller made the appropriate
// access calls.
- hsa_status_t Status;
if (InputSignal && InputSignal->load()) {
hsa_signal_t InputSignalRaw = InputSignal->get();
- Status =
- hsa_amd_memory_async_copy(Dst, DstAgent, Src, SrcAgent, CopySize, 1,
- &InputSignalRaw, OutputSignal->get());
- } else
- Status = hsa_amd_memory_async_copy(Dst, DstAgent, Src, SrcAgent, CopySize,
- 0, nullptr, OutputSignal->get());
-
- return Plugin::check(Status, "Error in D2D hsa_amd_memory_async_copy: %s");
+ return utils::asyncMemCopy(UseMultipleSdmaEngines, Dst, DstAgent, Src,
+ SrcAgent, CopySize, 1, &InputSignalRaw,
+ OutputSignal->get());
+ }
+ return utils::asyncMemCopy(UseMultipleSdmaEngines, Dst, DstAgent, Src,
+ SrcAgent, CopySize, 0, nullptr,
+ OutputSignal->get());
}
/// Synchronize with the stream. The current thread waits until all operations
@@ -1788,6 +1824,8 @@ struct AMDGPUDeviceTy : public GenericDeviceTy, AMDGenericDeviceTy {
OMPX_InitialNumSignals("LIBOMPTARGET_AMDGPU_NUM_INITIAL_HSA_SIGNALS",
64),
OMPX_StreamBusyWait("LIBOMPTARGET_AMDGPU_STREAM_BUSYWAIT", 2000000),
+ OMPX_UseMultipleSdmaEngines(
+ "LIBOMPTARGET_AMDGPU_USE_MULTIPLE_SDMA_ENGINES", false),
AMDGPUStreamManager(*this, Agent), AMDGPUEventManager(*this),
AMDGPUSignalManager(*this), Agent(Agent), HostDevice(HostDevice) {}
@@ -2206,10 +2244,9 @@ struct AMDGPUDeviceTy : public GenericDeviceTy, AMDGenericDeviceTy {
if (auto Err = Signal.init())
return Err;
- Status = hsa_amd_memory_async_copy(TgtPtr, Agent, PinnedPtr, Agent, Size,
- 0, nullptr, Signal.get());
- if (auto Err =
- Plugin::check(Status, "Error in hsa_amd_memory_async_copy: %s"))
+ if (auto Err = utils::asyncMemCopy(useMultipleSdmaEngines(), TgtPtr,
+ Agent, PinnedPtr, Agent, Size, 0,
+ nullptr, Signal.get()))
return Err;
if (auto Err = Signal.wait(getStreamBusyWaitMicroseconds()))
@@ -2267,10 +2304,9 @@ struct AMDGPUDeviceTy : public GenericDeviceTy, AMDGenericDeviceTy {
if (auto Err = Signal.init())
return Err;
- Status = hsa_amd_memory_async_copy(PinnedPtr, Agent, TgtPtr, Agent, Size,
- 0, nullptr, Signal.get());
- if (auto Err =
- Plugin::check(Status, "Error in hsa_amd_memory_async_copy: %s"))
+ if (auto Err = utils::asyncMemCopy(useMultipleSdmaEngines(), PinnedPtr,
+ Agent, TgtPtr, Agent, Size, 0, nullptr,
+ Signal.get()))
return Err;
if (auto Err = Signal.wait(getStreamBusyWaitMicroseconds()))
@@ -2633,6 +2669,8 @@ struct AMDGPUDeviceTy : public GenericDeviceTy, AMDGenericDeviceTy {
});
}
+ bool useMultipleSdmaEngines() const { return OMPX_UseMultipleSdmaEngines; }
+
private:
using AMDGPUEventRef = AMDGPUResourceRef<AMDGPUEventTy>;
using AMDGPUEventManagerTy = GenericDeviceResourceManagerTy<AMDGPUEventRef>;
@@ -2702,6 +2740,9 @@ struct AMDGPUDeviceTy : public GenericDeviceTy, AMDGenericDeviceTy {
/// are microseconds.
UInt32Envar OMPX_StreamBusyWait;
+ /// Use ROCm 5.7 interface for multiple SDMA engines
+ BoolEnvar OMPX_UseMultipleSdmaEngines;
+
/// Stream manager for AMDGPU streams.
AMDGPUStreamManagerTy AMDGPUStreamManager;
@@ -2803,7 +2844,8 @@ AMDGPUStreamTy::AMDGPUStreamTy(AMDGPUDeviceTy &Device)
SignalManager(Device.getSignalManager()), Device(Device),
// Initialize the std::deque with some empty positions.
Slots(32), NextSlot(0), SyncCycle(0), RPCServer(nullptr),
- StreamBusyWaitMicroseconds(Device.getStreamBusyWaitMicroseconds()) {}
+ StreamBusyWaitMicroseconds(Device.getStreamBusyWaitMicroseconds()),
+ UseMultipleSdmaEngines(Device.useMultipleSdmaEngines()) {}
/// Class implementing the AMDGPU-specific functionalities of the global
/// handler.
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