fixup! small cleanp

Author: Pablo Galindo Salgado

Modules/_remote_debugging/_remote_debugging.h

@@ -242,6 +242,7 @@ typedef struct {
 typedef struct {
     uintptr_t interpreter_addr;
     uintptr_t thread_state_addr;
+    uint64_t code_object_generation;
 } InterpreterThreadCacheEntry;
 
 // Carries already-read thread state and/or frame buffers across helpers so the
@@ -288,7 +289,8 @@ typedef struct {
 #define STATS_ADD(unwinder, field, val) \
     do { if (REMOTE_DEBUG_UNLIKELY((unwinder)->collect_stats)) (unwinder)->stats.field += (val); } while(0)
 
-#define STATS_BATCHED_READ(unwinder, requested, completed) \
+#if HAVE_PROCESS_VM_READV
+#  define STATS_BATCHED_READ(unwinder, requested, completed) \
     do { \
         if (REMOTE_DEBUG_UNLIKELY((unwinder)->collect_stats)) { \
             (unwinder)->stats.batched_read_attempts++; \
@@ -302,6 +304,9 @@ typedef struct {
             } \
         } \
     } while(0)
+#else
+#  define STATS_BATCHED_READ(unwinder, requested, completed) ((void)0)
+#endif
 
 typedef struct {
     PyTypeObject *RemoteDebugging_Type;
@@ -342,7 +347,6 @@ typedef struct {
     struct _Py_AsyncioModuleDebugOffsets async_debug_offsets;
     uintptr_t interpreter_addr;
     uintptr_t tstate_addr;
-    uint64_t code_object_generation;
     _Py_hashtable_t *code_object_cache;
     int debug;
     int only_active_thread;
@@ -355,9 +359,11 @@ typedef struct {
     int collect_stats;  // whether to collect statistics
     uint32_t stale_invalidation_counter;  // counter for throttling frame_cache_invalidate_stale
     // L1 single-entry shortcut over cached_tstates[]: most workloads sample one
-    // interpreter, so check this pair before hashing into the table below.
+    // interpreter, so check these pairs before hashing into the table below.
     uintptr_t cached_tstate_interpreter_addr;
     uintptr_t cached_tstate_addr;
+    uintptr_t cached_generation_interpreter_addr;
+    uint64_t cached_code_object_generation;
     RemoteDebuggingState *cached_state;
     FrameCacheEntry *frame_cache;  // preallocated array of FRAME_CACHE_MAX_THREADS entries
     UnwinderStats stats;  // statistics for performance analysis

Modules/_remote_debugging/module.c

@@ -532,14 +532,34 @@ set_cached_tstate_for_interpreter(
 static void
 refresh_generation_caches_from_interp_state(
     RemoteUnwinderObject *self,
+    uintptr_t interpreter_addr,
     const char *interp_state_buffer)
 {
     uint64_t code_object_generation = GET_MEMBER(uint64_t, interp_state_buffer,
             self->debug_offsets.interpreter_state.code_object_generation);
 
-    if (code_object_generation != self->code_object_generation) {
-        self->code_object_generation = code_object_generation;
-        _Py_hashtable_clear(self->code_object_cache);
+    if (self->cached_generation_interpreter_addr == interpreter_addr) {
+        if (code_object_generation != self->cached_code_object_generation) {
+            self->cached_code_object_generation = code_object_generation;
+            _Py_hashtable_clear(self->code_object_cache);
+        }
+    }
+    else {
+        InterpreterThreadCacheEntry *entry =
+            &self->cached_tstates[interpreter_thread_cache_index(interpreter_addr)];
+        uint64_t prev_generation = 0;
+        if (entry->interpreter_addr == interpreter_addr) {
+            prev_generation = entry->code_object_generation;
+        }
+        else {
+            entry->interpreter_addr = interpreter_addr;
+        }
+        entry->code_object_generation = code_object_generation;
+        if (code_object_generation != prev_generation) {
+            _Py_hashtable_clear(self->code_object_cache);
+        }
+        self->cached_generation_interpreter_addr = interpreter_addr;
+        self->cached_code_object_generation = code_object_generation;
     }
 
 #ifdef Py_GIL_DISABLED
@@ -567,7 +587,7 @@ refresh_generation_caches_for_interpreter(
                             "Failed to read interpreter state buffer");
         return -1;
     }
-    refresh_generation_caches_from_interp_state(self, interp_state_buffer);
+    refresh_generation_caches_from_interp_state(self, interpreter_addr, interp_state_buffer);
     return 0;
 }
 
@@ -712,7 +732,7 @@ _remote_debugging_RemoteUnwinder_get_stack_trace_impl(RemoteUnwinderObject *self
             Py_CLEAR(result);
             goto exit;
         }
-        refresh_generation_caches_from_interp_state(self, interp_state_buffer);
+        refresh_generation_caches_from_interp_state(self, current_interpreter, interp_state_buffer);
 
         uintptr_t gc_frame = 0;
         if (self->gc) {