Enable optimized single-proc allocation helpers for single-proc x86/x64 systems only (#27014) (#27080)

Use maximum number of processors the process may run on to determine whether it is ok to use
single-proc allocation helpers. It is not sufficient to depend on current process affinity since
that can change during the process lifetime.

Also, the single-proc allocation helpers work well on x86/x64 systems only because of they depend
on atomic non-interlocked increment instruction for good performance. Such instruction is available
on x86/x64 only. Disable them everywhere else.

Fixes #26990

1 files changed, 4 insertions, 4 deletions

diff --git a/src/vm/gcheaputilities.h b/src/vm/gcheaputilities.h
index 40889e9209..11f066c512 100644
--- a/src/vm/gcheaputilities.h
+++ b/src/vm/gcheaputilities.h
@@ -122,12 +122,12 @@ public:
 
     static bool UseThreadAllocationContexts()
     {
-        // When running on a single-proc system, it's more efficient to use a single global
+        // When running on a single-proc Intel system, it's more efficient to use a single global
         // allocation context for SOH allocations than to use one for every thread.
-#if defined(_TARGET_ARM_) || defined(FEATURE_PAL) || defined(FEATURE_REDHAWK)
-        return true;
+#if (defined(_TARGET_X86_) || defined(_TARGET_AMD64_)) && !defined(FEATURE_PAL)
+        return IsServerHeap() || ::g_SystemInfo.dwNumberOfProcessors != 1 || CPUGroupInfo::CanEnableGCCPUGroups();
 #else
-        return IsServerHeap() || ::GetCurrentProcessCpuCount() != 1;
+        return true;
 #endif
 
     }