gh-91048: Fix external inspection multi-threaded performance (#136005)

Python/remote_debug.h

@@ -110,14 +110,6 @@ get_page_size(void) {
     return page_size;
 }
 
-typedef struct page_cache_entry {
-    uintptr_t page_addr; // page-aligned base address
-    char *data;
-    int valid;
-    struct page_cache_entry *next;
-} page_cache_entry_t;
-
-#define MAX_PAGES 1024
 
 // Define a platform-independent process handle structure
 typedef struct {
@@ -129,27 +121,9 @@ typedef struct {
 #elif defined(__linux__)
     int memfd;
 #endif
-    page_cache_entry_t pages[MAX_PAGES];
     Py_ssize_t page_size;
 } proc_handle_t;
 
-static void
-_Py_RemoteDebug_FreePageCache(proc_handle_t *handle)
-{
-    for (int i = 0; i < MAX_PAGES; i++) {
-        PyMem_RawFree(handle->pages[i].data);
-        handle->pages[i].data = NULL;
-        handle->pages[i].valid = 0;
-    }
-}
-
-UNUSED static void
-_Py_RemoteDebug_ClearCache(proc_handle_t *handle)
-{
-    for (int i = 0; i < MAX_PAGES; i++) {
-        handle->pages[i].valid = 0;
-    }
-}
 
 #if defined(__APPLE__) && defined(TARGET_OS_OSX) && TARGET_OS_OSX
 static mach_port_t pid_to_task(pid_t pid);
@@ -178,10 +152,6 @@ _Py_RemoteDebug_InitProcHandle(proc_handle_t *handle, pid_t pid) {
     handle->memfd = -1;
 #endif
     handle->page_size = get_page_size();
-    for (int i = 0; i < MAX_PAGES; i++) {
-        handle->pages[i].data = NULL;
-        handle->pages[i].valid = 0;
-    }
     return 0;
 }
 
@@ -200,7 +170,6 @@ _Py_RemoteDebug_CleanupProcHandle(proc_handle_t *handle) {
     }
 #endif
     handle->pid = 0;
-    _Py_RemoteDebug_FreePageCache(handle);
 }
 
 #if defined(__APPLE__) && defined(TARGET_OS_OSX) && TARGET_OS_OSX
@@ -1066,53 +1035,6 @@ _Py_RemoteDebug_PagedReadRemoteMemory(proc_handle_t *handle,
                                       size_t size,
                                       void *out)
 {
-    size_t page_size = handle->page_size;
-    uintptr_t page_base = addr & ~(page_size - 1);
-    size_t offset_in_page = addr - page_base;
-
-    if (offset_in_page + size > page_size) {
-        return _Py_RemoteDebug_ReadRemoteMemory(handle, addr, size, out);
-    }
-
-    // Search for valid cached page
-    for (int i = 0; i < MAX_PAGES; i++) {
-        page_cache_entry_t *entry = &handle->pages[i];
-        if (entry->valid && entry->page_addr == page_base) {
-            memcpy(out, entry->data + offset_in_page, size);
-            return 0;
-        }
-    }
-
-    // Find reusable slot
-    for (int i = 0; i < MAX_PAGES; i++) {
-        page_cache_entry_t *entry = &handle->pages[i];
-        if (!entry->valid) {
-            if (entry->data == NULL) {
-                entry->data = PyMem_RawMalloc(page_size);
-                if (entry->data == NULL) {
-                    _set_debug_exception_cause(PyExc_MemoryError,
-                        "Cannot allocate %zu bytes for page cache entry "
-                        "during read from PID %d at address 0x%lx",
-                        page_size, handle->pid, addr);
-                    return -1;
-                }
-            }
-
-            if (_Py_RemoteDebug_ReadRemoteMemory(handle, page_base, page_size, entry->data) < 0) {
-                // Try to just copy the exact ammount as a fallback
-                PyErr_Clear();
-                goto fallback;
-            }
-
-            entry->page_addr = page_base;
-            entry->valid = 1;
-            memcpy(out, entry->data + offset_in_page, size);
-            return 0;
-        }
-    }
-
-fallback:
-    // Cache full — fallback to uncached read
     return _Py_RemoteDebug_ReadRemoteMemory(handle, addr, size, out);
 }