Speed-up JIT dump

Add a config option that allows routing JIT's stdout output to a
specified file. jitStartup disables stdio buffering on its stdout
created stream and that makes large dumps (such as the ones generated
by jit-diff) 2-4x slower. Simply enabling buffering is somewhat
problematic, it would require occasional flushing to avoid losing
output in the case of a crash and can also result in mingled output
if crossgen decides to print something via its own stdout stream.

file

fix

Commit migrated from https://github.com/dotnet/coreclr/commit/193e3134e3726b933111b46617be9bee05084ee2

diff --git a/src/coreclr/src/jit/ee_il_dll.cpp b/src/coreclr/src/jit/ee_il_dll.cpp
index 88612bc..5153363 100644 (file)
--- a/src/coreclr/src/jit/ee_il_dll.cpp
+++ b/src/coreclr/src/jit/ee_il_dll.cpp
@@ -80,9 +80,16 @@ extern "C" void __stdcall jitStartup(ICorJitHost* jitHost)
     assert(!JitConfig.isInitialized());
     JitConfig.initialize(jitHost);
 
-#if defined(_HOST_UNIX_)
-    jitstdout = procstdout();
-#else  // !_HOST_UNIX_
+#ifdef DEBUG
+    const wchar_t* jitStdOutFile = JitConfig.JitStdOutFile();
+    if (jitStdOutFile != nullptr)
+    {
+        jitstdout = _wfopen(jitStdOutFile, W("a"));
+        assert(jitstdout != nullptr);
+    }
+#endif // DEBUG
+
+#if !defined(_HOST_UNIX_)
     if (jitstdout == nullptr)
     {
         int stdoutFd = _fileno(procstdout());
@@ -106,6 +113,7 @@ extern "C" void __stdcall jitStartup(ICorJitHost* jitHost)
             }
         }
     }
+#endif // !_HOST_UNIX_
 
     // If jitstdout is still null, fallback to whatever procstdout() was
     // initially set to.
@@ -113,7 +121,6 @@ extern "C" void __stdcall jitStartup(ICorJitHost* jitHost)
     {
         jitstdout = procstdout();
     }
-#endif // !_HOST_UNIX_
 
 #ifdef FEATURE_TRACELOGGING
     JitTelemetry::NotifyDllProcessAttach();

diff --git a/src/coreclr/src/jit/jitconfigvalues.h b/src/coreclr/src/jit/jitconfigvalues.h
index 26c5ccc..49b8c7a 100644 (file)
--- a/src/coreclr/src/jit/jitconfigvalues.h
+++ b/src/coreclr/src/jit/jitconfigvalues.h
@@ -113,6 +113,7 @@ CONFIG_INTEGER(JitSplitFunctionSize, W("JitSplitFunctionSize"), 0) // On ARM, us
 CONFIG_INTEGER(JitSsaStress, W("JitSsaStress"), 0) // Perturb order of processing of blocks in SSA; 0 = no stress; 1 =
                                                    // use method hash; * = supplied value as random hash
 CONFIG_INTEGER(JitStackChecks, W("JitStackChecks"), 0)
+CONFIG_STRING(JitStdOutFile, W("JitStdOutFile")) // If set, sends JIT's stdout output to this file.
 CONFIG_INTEGER(JitStress, W("JitStress"), 0) // Internal Jit stress mode: 0 = no stress, 2 = all stress, other = vary
                                              // stress based on a hash of the method and this value
 CONFIG_INTEGER(JitStressBBProf, W("JitStressBBProf"), 0)               // Internal Jit stress mode