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Merge pull request #3091 from Subv/hle_request_delat

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Kernel/IPC: Add a small delay after each SyncRequest to prevent thread starvation.
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B3n30 2017-12-10 19:59:19 +01:00 committed by GitHub
commit 2146311ad1
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1 changed files with 23 additions and 5 deletions
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28
src/core/hle/kernel/server_session.cpp
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@ -67,13 +67,31 @@ ResultCode ServerSession::HandleSyncRequest(SharedPtr<Thread> thread) {
// If this ServerSession has an associated HLE handler, forward the request to it.
if (hle_handler != nullptr) {
hle_handler->HandleSyncRequest(SharedPtr<ServerSession>(this));
} else {
}
if (thread->status == THREADSTATUS_RUNNING) {
// Put the thread to sleep until the server replies, it will be awoken in
// svcReplyAndReceive.
// svcReplyAndReceive for LLE servers.
thread->status = THREADSTATUS_WAIT_IPC;
// Add the thread to the list of threads that have issued a sync request with this
// server.
pending_requesting_threads.push_back(std::move(thread));
if (hle_handler != nullptr) {
// For HLE services, we put the request threads to sleep for a short duration to
// simulate IPC overhead, but only if the HLE handler didn't put the thread to sleep for
// other reasons like an async callback. The IPC overhead is needed to prevent
// starvation when a thread only does sync requests to HLE services while a
// lower-priority thread is waiting to run.
// This delay was approximated in a homebrew application by measuring the average time
// it takes for svcSendSyncRequest to return when performing the SetLcdForceBlack IPC
// request to the GSP:GPU service in a n3DS with firmware 11.6. The measured values have
// a high variance and vary between models.
static constexpr u64 IPCDelayNanoseconds = 39000;
thread->WakeAfterDelay(IPCDelayNanoseconds);
} else {
// Add the thread to the list of threads that have issued a sync request with this
// server.
pending_requesting_threads.push_back(std::move(thread));
}
}
// If this ServerSession does not have an HLE implementation, just wake up the threads waiting