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//===- RPC.h - Interface for remote procedure calls from the GPU ----------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "RPC.h"
#include "Shared/Debug.h"
#include "Shared/RPCOpcodes.h"
#include "PluginInterface.h"
#include "shared/rpc.h"
#include "shared/rpc_opcodes.h"
#include "shared/rpc_server.h"
using namespace llvm;
using namespace omp;
using namespace target;
template <uint32_t NumLanes>
rpc::Status handleOffloadOpcodes(plugin::GenericDeviceTy &Device,
rpc::Server::Port &Port) {
switch (Port.get_opcode()) {
case LIBC_MALLOC: {
Port.recv_and_send([&](rpc::Buffer *Buffer, uint32_t) {
auto PtrOrErr =
Device.allocate(Buffer->data[0], nullptr, TARGET_ALLOC_DEVICE);
void *Ptr = nullptr;
if (!PtrOrErr)
llvm::consumeError(PtrOrErr.takeError());
else
Ptr = *PtrOrErr;
Buffer->data[0] = reinterpret_cast<uintptr_t>(Ptr);
});
break;
}
case LIBC_FREE: {
Port.recv([&](rpc::Buffer *Buffer, uint32_t) {
if (auto Err = Device.free(reinterpret_cast<void *>(Buffer->data[0]),
TARGET_ALLOC_DEVICE))
llvm::consumeError(std::move(Err));
});
break;
}
case OFFLOAD_HOST_CALL: {
uint64_t Sizes[NumLanes] = {0};
unsigned long long Results[NumLanes] = {0};
void *Args[NumLanes] = {nullptr};
Port.recv_n(Args, Sizes, [&](uint64_t Size) { return new char[Size]; });
Port.recv([&](rpc::Buffer *buffer, uint32_t ID) {
using FuncPtrTy = unsigned long long (*)(void *);
auto Func = reinterpret_cast<FuncPtrTy>(buffer->data[0]);
Results[ID] = Func(Args[ID]);
});
Port.send([&](rpc::Buffer *Buffer, uint32_t ID) {
Buffer->data[0] = static_cast<uint64_t>(Results[ID]);
delete[] reinterpret_cast<char *>(Args[ID]);
});
break;
}
default:
return rpc::RPC_UNHANDLED_OPCODE;
break;
}
return rpc::RPC_SUCCESS;
}
static rpc::Status handleOffloadOpcodes(plugin::GenericDeviceTy &Device,
rpc::Server::Port &Port,
uint32_t NumLanes) {
if (NumLanes == 1)
return handleOffloadOpcodes<1>(Device, Port);
else if (NumLanes == 32)
return handleOffloadOpcodes<32>(Device, Port);
else if (NumLanes == 64)
return handleOffloadOpcodes<64>(Device, Port);
else
return rpc::RPC_ERROR;
}
static rpc::Status runServer(plugin::GenericDeviceTy &Device, void *Buffer,
bool &ClientInUse) {
uint64_t NumPorts =
std::min(Device.requestedRPCPortCount(), rpc::MAX_PORT_COUNT);
rpc::Server Server(NumPorts, Buffer);
auto Port = Server.try_open(Device.getWarpSize());
if (!Port)
return rpc::RPC_SUCCESS;
ClientInUse = true;
rpc::Status Status =
handleOffloadOpcodes(Device, *Port, Device.getWarpSize());
// Let the `libc` library handle any other unhandled opcodes.
if (Status == rpc::RPC_UNHANDLED_OPCODE)
Status = LIBC_NAMESPACE::shared::handle_libc_opcodes(*Port,
Device.getWarpSize());
Port->close();
return Status;
}
void RPCServerTy::ServerThread::startThread() {
if (!Running.fetch_or(true, std::memory_order_acquire))
Worker = std::thread([this]() { run(); });
}
void RPCServerTy::ServerThread::shutDown() {
if (!Running.fetch_and(false, std::memory_order_release))
return;
{
std::lock_guard<decltype(Mutex)> Lock(Mutex);
CV.notify_all();
}
if (Worker.joinable())
Worker.join();
}
void RPCServerTy::ServerThread::run() {
static constexpr auto IdleTime = std::chrono::microseconds(25);
static constexpr auto IdleSleep = std::chrono::microseconds(250);
std::unique_lock<decltype(Mutex)> Lock(Mutex);
auto LastUse = std::chrono::steady_clock::now();
for (;;) {
CV.wait(Lock, [&]() {
return NumUsers.load(std::memory_order_acquire) > 0 ||
!Running.load(std::memory_order_acquire);
});
if (!Running.load(std::memory_order_acquire))
return;
Lock.unlock();
bool ClientInUse = false;
while (NumUsers.load(std::memory_order_relaxed) > 0 &&
Running.load(std::memory_order_relaxed)) {
// Suspend this thread briefly if there is no current work.
auto Now = std::chrono::steady_clock::now();
if (!ClientInUse && Now - LastUse >= IdleTime)
std::this_thread::sleep_for(IdleSleep);
else if (ClientInUse)
LastUse = Now;
ClientInUse = false;
std::lock_guard<decltype(Mutex)> Lock(BufferMutex);
for (const auto &[Buffer, Device] : llvm::zip_equal(Buffers, Devices)) {
if (!Buffer || !Device)
continue;
// If running the server failed, print a message but keep running.
if (runServer(*Device, Buffer, ClientInUse) != rpc::RPC_SUCCESS)
FAILURE_MESSAGE("Unhandled or invalid RPC opcode!");
}
}
Lock.lock();
}
}
RPCServerTy::RPCServerTy(plugin::GenericPluginTy &Plugin)
: Buffers(std::make_unique<void *[]>(Plugin.getNumDevices())),
Devices(std::make_unique<plugin::GenericDeviceTy *[]>(
Plugin.getNumDevices())),
Thread(new ServerThread(Buffers.get(), Devices.get(),
Plugin.getNumDevices(), BufferMutex)) {}
llvm::Error RPCServerTy::startThread() {
Thread->startThread();
return Error::success();
}
llvm::Error RPCServerTy::shutDown() {
Thread->shutDown();
return Error::success();
}
llvm::Expected<bool>
RPCServerTy::isDeviceUsingRPC(plugin::GenericDeviceTy &Device,
plugin::GenericGlobalHandlerTy &Handler,
plugin::DeviceImageTy &Image) {
return Handler.isSymbolInImage(Device, Image, "__llvm_rpc_client");
}
Error RPCServerTy::initDevice(plugin::GenericDeviceTy &Device,
plugin::GenericGlobalHandlerTy &Handler,
plugin::DeviceImageTy &Image) {
uint64_t NumPorts =
std::min(Device.requestedRPCPortCount(), rpc::MAX_PORT_COUNT);
auto RPCBufferOrErr = Device.allocate(
rpc::Server::allocation_size(Device.getWarpSize(), NumPorts), nullptr,
TARGET_ALLOC_HOST);
if (!RPCBufferOrErr)
return RPCBufferOrErr.takeError();
void *RPCBuffer = *RPCBufferOrErr;
if (!RPCBuffer)
return plugin::Plugin::error(
error::ErrorCode::UNKNOWN,
"failed to initialize RPC server for device %d", Device.getDeviceId());
// Get the address of the RPC client from the device.
plugin::GlobalTy ClientGlobal("__llvm_rpc_client", sizeof(rpc::Client));
if (auto Err =
Handler.getGlobalMetadataFromDevice(Device, Image, ClientGlobal))
return Err;
rpc::Client client(NumPorts, RPCBuffer);
if (auto Err = Device.dataSubmit(ClientGlobal.getPtr(), &client,
sizeof(rpc::Client), nullptr))
return Err;
std::lock_guard<decltype(BufferMutex)> Lock(BufferMutex);
Buffers[Device.getDeviceId()] = RPCBuffer;
Devices[Device.getDeviceId()] = &Device;
return Error::success();
}
Error RPCServerTy::deinitDevice(plugin::GenericDeviceTy &Device) {
std::lock_guard<decltype(BufferMutex)> Lock(BufferMutex);
if (auto Err = Device.free(Buffers[Device.getDeviceId()], TARGET_ALLOC_HOST))
return Err;
Buffers[Device.getDeviceId()] = nullptr;
Devices[Device.getDeviceId()] = nullptr;
return Error::success();
}
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