[libc-commits] [PATCH] D150065: [libc][rpc][nfc] Change to private mailbox pointers
Jon Chesterfield via Phabricator via libc-commits
libc-commits at lists.llvm.org
Sun May 7 07:03:45 PDT 2023
JonChesterfield updated this revision to Diff 520181.
JonChesterfield added a comment.
- comments
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D150065/new/
https://reviews.llvm.org/D150065
Files:
libc/src/__support/RPC/rpc.h
Index: libc/src/__support/RPC/rpc.h
===================================================================
--- libc/src/__support/RPC/rpc.h
+++ libc/src/__support/RPC/rpc.h
@@ -106,11 +106,14 @@
uint64_t port_count;
uint32_t lane_size;
+
+private:
cpp::Atomic<uint32_t> *lock;
cpp::Atomic<uint32_t> *inbox;
cpp::Atomic<uint32_t> *outbox;
Packet *packet;
+public:
/// Initialize the communication channels.
LIBC_INLINE void reset(uint64_t port_count, uint32_t lane_size, void *lock,
void *inbox, void *outbox, void *packet) {
@@ -146,6 +149,22 @@
return InvertInbox ? !i : i;
}
+ /// Retrieve the outbox state from memory shared between processes.
+ /// Never needs to invert the associated read.
+ LIBC_INLINE uint32_t load_outbox(uint64_t index) {
+ return outbox[index].load(cpp::MemoryOrder::RELAXED);
+ }
+
+ /// Signal to the other process that this one is finished with the buffer.
+ /// Equivalent to loading outbox followed by store of the inverted value
+ /// The outbox is write only by this warp and tracking the value locally is
+ /// cheaper than calling load_outbox to get the value to store.
+ LIBC_INLINE uint32_t invert_outbox(uint64_t index, uint32_t current_outbox) {
+ uint32_t inverted_outbox = !current_outbox;
+ outbox[index].store(inverted_outbox, cpp::MemoryOrder::RELAXED);
+ return inverted_outbox;
+ }
+
/// Determines if this process needs to wait for ownership of the buffer.
LIBC_INLINE static bool buffer_unavailable(uint32_t in, uint32_t out) {
return in != out;
@@ -301,9 +320,8 @@
// Apply the \p fill function to initialize the buffer and release the memory.
process.invoke_rpc(fill, process.get_packet(index));
- out = !out;
atomic_thread_fence(cpp::MemoryOrder::RELEASE);
- process.outbox[index].store(out, cpp::MemoryOrder::RELAXED);
+ out = process.invert_outbox(index, out);
}
/// Applies \p use to the shared buffer and acknowledges the send.
@@ -319,8 +337,7 @@
// Apply the \p use function to read the memory out of the buffer.
process.invoke_rpc(use, process.get_packet(index));
- out = !out;
- process.outbox[index].store(out, cpp::MemoryOrder::RELAXED);
+ out = process.invert_outbox(index, out);
}
/// Combines a send and receive into a single function.
@@ -426,7 +443,7 @@
atomic_thread_fence(cpp::MemoryOrder::ACQUIRE);
uint32_t in = load_inbox(index);
- uint32_t out = outbox[index].load(cpp::MemoryOrder::RELAXED);
+ uint32_t out = load_outbox(index);
// Once we acquire the index we need to check if we are in a valid sending
// state.
@@ -460,7 +477,7 @@
// Perform a naive linear scan for a port that has a pending request.
for (uint64_t index = 0; index < port_count; ++index) {
uint32_t in = load_inbox(index);
- uint32_t out = outbox[index].load(cpp::MemoryOrder::RELAXED);
+ uint32_t out = load_outbox(index);
// The server is passive, if there is no work pending don't bother
// opening a port.
@@ -477,7 +494,7 @@
atomic_thread_fence(cpp::MemoryOrder::ACQUIRE);
in = load_inbox(index);
- out = outbox[index].load(cpp::MemoryOrder::RELAXED);
+ out = load_outbox(index);
if (buffer_unavailable(in, out)) {
unlock(lane_mask, index);
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