From 729e4c2abd4ab4eda4051579c57410dd64d4e7a9 Mon Sep 17 00:00:00 2001
From: Cory Fields <cory-nospam-@coryfields.com>
Date: Wed, 1 Oct 2025 16:14:08 +0000
Subject: [PATCH] multiprocess: align our logging with libmultiprocess's

Without this change, logging (even if unused) may account for a
substantial portion of bitcoin-node's and/or client's runtime cpu usage, due
to libmultiprocess's expensive message serialization.

This (along with some recent upstream changes) avoids the overhead by opting
out of log handling for messages that we're not interested in.

Info, Warning, and Error are logged unconditionally to match our behavior
elsewhere. See BCLog::Logger::GetCategoryLogLevel .

Github-Pull: #33517
Rebased-From: 0626b90f507db68610a69feec86deb712dd095a1
---
 src/ipc/capnp/protocol.cpp | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/ipc/capnp/protocol.cpp b/src/ipc/capnp/protocol.cpp
index 4263aebd284..27ef73e84e5 100644
--- a/src/ipc/capnp/protocol.cpp
+++ b/src/ipc/capnp/protocol.cpp
@@ -30,9 +30,35 @@
 namespace ipc {
 namespace capnp {
 namespace {
+
+BCLog::Level ConvertIPCLogLevel(mp::Log level)
+{
+    switch (level) {
+        case mp::Log::Trace: return BCLog::Level::Trace;
+        case mp::Log::Debug: return BCLog::Level::Debug;
+        case mp::Log::Info: return BCLog::Level::Info;
+        case mp::Log::Warning: return BCLog::Level::Warning;
+        case mp::Log::Error: return BCLog::Level::Error;
+        case mp::Log::Raise: return BCLog::Level::Error;
+    } // no default case, so the compiler can warn about missing cases
+
+    // Be conservative and assume that if MP ever adds a new log level, it
+    // should only be shown at our most verbose level.
+    return BCLog::Level::Trace;
+}
+
+mp::Log GetRequestedIPCLogLevel()
+{
+    if (LogAcceptCategory(BCLog::IPC, BCLog::Level::Trace)) return mp::Log::Trace;
+    if (LogAcceptCategory(BCLog::IPC, BCLog::Level::Debug)) return mp::Log::Debug;
+
+    // Info, Warning, and Error are logged unconditionally
+    return mp::Log::Info;
+}
+
 void IpcLogFn(mp::LogMessage message)
 {
-    LogDebug(BCLog::IPC, "%s\n", message.message);
+    LogPrintLevel(BCLog::IPC, ConvertIPCLogLevel(message.level), "%s\n", message.message);
     if (message.level == mp::Log::Raise) throw Exception(message.message);
 }
 
@@ -64,6 +90,7 @@ public:
         mp::g_thread_context.thread_name = mp::ThreadName(exe_name);
         mp::LogOptions opts = {
             .log_fn = IpcLogFn,
+            .log_level = GetRequestedIPCLogLevel()
         };
         m_loop.emplace(exe_name, std::move(opts), &m_context);
         if (ready_fn) ready_fn();
@@ -95,6 +122,7 @@ public:
             util::ThreadRename("capnp-loop");
             mp::LogOptions opts = {
                 .log_fn = IpcLogFn,
+                .log_level = GetRequestedIPCLogLevel()
             };
             m_loop.emplace(exe_name, std::move(opts), &m_context);
             m_loop_ref.emplace(*m_loop);