From 45978474f3d9e7e0d0eddca86121a2a0e5dfeccc Mon Sep 17 00:00:00 2001
From: Ryan Houdek <Sonicadvance1@gmail.com>
Date: Sun, 5 Oct 2025 17:07:48 -0700
Subject: [PATCH] Allocator: Name FEX's VMA regions for allocation

Will allow external tools to track how much memory FEX allocates.
Necessary since we can't use traditional memory usage tools to track FEX
memory allocation independently of guest allocations. Plus most tools
like heaptrack hook allocation symbols, which break under jemalloc.

Using this information I can see with Steam loaded with my library that
FEX consumes ~825MB. Total process resident memory is 1204M, accounting
for around 379MB being used by steam itself. This is /relatively/ close
to my desktop running steam at around 261MB. There's a bit of variance
due to what Steam chooses to do at startup.

This tracking will be the first step towards seeing where our memory
usage is going.
---
 FEXCore/Source/Interface/Core/CPUBackend.cpp |  6 ++++++
 FEXCore/Source/Utils/Allocator.cpp           |  5 +++++
 FEXCore/Source/Utils/PrctlUtils.h            | 17 +++++++++++++++++
 3 files changed, 28 insertions(+)
 create mode 100644 FEXCore/Source/Utils/PrctlUtils.h

diff --git a/FEXCore/Source/Interface/Core/CPUBackend.cpp b/FEXCore/Source/Interface/Core/CPUBackend.cpp
index 7e30d712f..2a6d2b8d0 100644
--- a/FEXCore/Source/Interface/Core/CPUBackend.cpp
+++ b/FEXCore/Source/Interface/Core/CPUBackend.cpp
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: MIT
 #include "FEXCore/IR/IR.h"
 #include "FEXCore/Utils/AllocatorHooks.h"
+#include "Utils/PrctlUtils.h"
 #include "Interface/Context/Context.h"
 #include "Interface/Core/CPUBackend.h"
 #include "Interface/Core/Dispatcher/Dispatcher.h"
@@ -9,6 +10,7 @@
 #include "LookupCache.h"
 
 #ifndef _WIN32
+#include <linux/prctl.h>
 #include <sys/prctl.h>
 #endif
 
@@ -357,6 +359,10 @@ namespace CPU {
       LogMan::Msg::EFmt("Failed to mprotect last page of code buffer.");
     }
 
+#ifndef _WIN32
+    prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, Ptr, Size, "FEXMemJIT");
+#endif
+
     LookupCache = fextl::make_unique<GuestToHostMap>();
   }
 
diff --git a/FEXCore/Source/Utils/Allocator.cpp b/FEXCore/Source/Utils/Allocator.cpp
index 062cdd444..47ccf59cb 100644
--- a/FEXCore/Source/Utils/Allocator.cpp
+++ b/FEXCore/Source/Utils/Allocator.cpp
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: MIT
 #include "Utils/Allocator/HostAllocator.h"
+#include "Utils/PrctlUtils.h"
 #include <FEXCore/Utils/Allocator.h>
 #include <FEXCore/Utils/CompilerDefs.h>
 #include <FEXCore/Utils/LogManager.h>
@@ -50,6 +51,10 @@ void* FEX_mmap(void* addr, size_t length, int prot, int flags, int fd, off_t off
     errno = -(uint64_t)Result;
     return (void*)-1;
   }
+
+  if (flags & MAP_ANONYMOUS) {
+    prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, Result, length, "FEXMem");
+  }
   return Result;
 }
 int FEX_munmap(void* addr, size_t length) {
diff --git a/FEXCore/Source/Utils/PrctlUtils.h b/FEXCore/Source/Utils/PrctlUtils.h
new file mode 100644
index 000000000..fdbe9238e
--- /dev/null
+++ b/FEXCore/Source/Utils/PrctlUtils.h
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: MIT
+#pragma once
+
+#ifndef _WIN32
+#include <linux/prctl.h>
+#include <sys/mman.h>
+#include <sys/user.h>
+#include <sys/prctl.h>
+
+#ifndef PR_SET_VMA
+#define PR_SET_VMA 0x53564d41
+#endif
+
+#ifndef PR_SET_VMA_ANON_NAME
+#define PR_SET_VMA_ANON_NAME 0
+#endif
+#endif