diff --git a/Misc/NEWS.d/next/Library/2026-05-10-19-26-50.gh-issue-149584.x7Qm9A.rst b/Misc/NEWS.d/next/Library/2026-05-10-19-26-50.gh-issue-149584.x7Qm9A.rst new file mode 100644 index 00000000000000..6734250fdd6af3 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-05-10-19-26-50.gh-issue-149584.x7Qm9A.rst @@ -0,0 +1,4 @@ +Fix excessive overhead in the Tachyon profiler when inspecting a remote +process by avoiding repeated remote page-cache scans, batching predicted +remote reads, and reusing cached profiler result objects. Patch by Pablo +Galindo and Maurycy Pawłowski-Wieroński. diff --git a/Modules/_remote_debugging/_remote_debugging.h b/Modules/_remote_debugging/_remote_debugging.h index 7369cd1514c296..422fe9e09873e8 100644 --- a/Modules/_remote_debugging/_remote_debugging.h +++ b/Modules/_remote_debugging/_remote_debugging.h @@ -215,6 +215,8 @@ typedef struct { PyObject *file_name; int first_lineno; PyObject *linetable; // bytes + PyObject *last_frame_info; + ptrdiff_t last_addrq; uintptr_t addr_code_adaptive; } CachedCodeMetadata; @@ -224,8 +226,10 @@ typedef struct { typedef struct { uint64_t thread_id; // 0 = empty slot + uintptr_t thread_state_addr; uintptr_t addrs[FRAME_CACHE_MAX_FRAMES]; Py_ssize_t num_addrs; + PyObject *thread_id_obj; // owned reference, NULL if empty PyObject *frame_list; // owned reference, NULL if empty } FrameCacheEntry; @@ -302,6 +306,7 @@ typedef struct { int cache_frames; int collect_stats; // whether to collect statistics uint32_t stale_invalidation_counter; // counter for throttling frame_cache_invalidate_stale + uintptr_t cached_tstate_addr; // predicted first thread for batched reads RemoteDebuggingState *cached_state; FrameCacheEntry *frame_cache; // preallocated array of FRAME_CACHE_MAX_THREADS entries UnwinderStats stats; // statistics for performance analysis @@ -361,11 +366,14 @@ typedef struct { typedef struct { /* Inputs */ uintptr_t frame_addr; // Starting frame address + uintptr_t thread_state_addr; // Owning thread state address uintptr_t base_frame_addr; // Sentinel at bottom (for validation) uintptr_t gc_frame; // GC frame address (0 if not tracking) uintptr_t last_profiled_frame; // Last cached frame (0 if no cache) StackChunkList *chunks; // Pre-copied stack chunks int skip_first_frame; // Skip frame_addr itself (continue from its caller) + const char *prefetched_frame; // Optional already-read frame buffer + uintptr_t prefetched_frame_addr; // Remote address for prefetched_frame /* Outputs */ PyObject *frame_info; // List to append FrameInfo objects @@ -548,6 +556,7 @@ extern int process_frame_chain( extern int frame_cache_init(RemoteUnwinderObject *unwinder); extern void frame_cache_cleanup(RemoteUnwinderObject *unwinder); extern FrameCacheEntry *frame_cache_find(RemoteUnwinderObject *unwinder, uint64_t thread_id); +extern FrameCacheEntry *frame_cache_find_by_tstate(RemoteUnwinderObject *unwinder, uintptr_t tstate_addr); extern int clear_last_profiled_frames(RemoteUnwinderObject *unwinder); extern void frame_cache_invalidate_stale(RemoteUnwinderObject *unwinder, PyObject *result); extern int frame_cache_lookup_and_extend( @@ -566,6 +575,7 @@ extern int frame_cache_store( PyObject *frame_list, const uintptr_t *addrs, Py_ssize_t num_addrs, + uintptr_t thread_state_addr, uintptr_t base_frame_addr, uintptr_t last_frame_visited); @@ -605,7 +615,11 @@ extern PyObject* unwind_stack_for_thread( uintptr_t *current_tstate, uintptr_t gil_holder_tstate, uintptr_t gc_frame, - uintptr_t main_thread_tstate + uintptr_t main_thread_tstate, + const char *prefetched_tstate, + uintptr_t prefetched_tstate_addr, + const char *prefetched_frame, + uintptr_t prefetched_frame_addr ); /* Thread stopping functions (for blocking mode) */ diff --git a/Modules/_remote_debugging/code_objects.c b/Modules/_remote_debugging/code_objects.c index 7b95c0f2d4fa8d..2ac6edb3f662f6 100644 --- a/Modules/_remote_debugging/code_objects.c +++ b/Modules/_remote_debugging/code_objects.c @@ -405,6 +405,8 @@ parse_code_object(RemoteUnwinderObject *unwinder, meta->func_name = func; meta->file_name = file; meta->linetable = linetable; + meta->last_frame_info = NULL; + meta->last_addrq = -1; meta->first_lineno = GET_MEMBER(int, code_object, unwinder->debug_offsets.code_object.firstlineno); meta->addr_code_adaptive = real_address + (uintptr_t)unwinder->debug_offsets.code_object.co_code_adaptive; @@ -482,6 +484,12 @@ parse_code_object(RemoteUnwinderObject *unwinder, addrq = (uint16_t *)ip - (uint16_t *)meta->addr_code_adaptive; #endif ; // Empty statement to avoid C23 extension warning + + if (!unwinder->opcodes && meta->last_frame_info != NULL && meta->last_addrq == addrq) { + *result = Py_NewRef(meta->last_frame_info); + return 0; + } + LocationInfo info = {0}; bool ok = parse_linetable(addrq, PyBytes_AS_STRING(meta->linetable), PyBytes_GET_SIZE(meta->linetable), @@ -529,6 +537,11 @@ parse_code_object(RemoteUnwinderObject *unwinder, goto error; } + if (!unwinder->opcodes) { + Py_XSETREF(meta->last_frame_info, Py_NewRef(tuple)); + meta->last_addrq = addrq; + } + *result = tuple; return 0; diff --git a/Modules/_remote_debugging/frame_cache.c b/Modules/_remote_debugging/frame_cache.c index b6566d7cff7b54..19fc406bca9ac9 100644 --- a/Modules/_remote_debugging/frame_cache.c +++ b/Modules/_remote_debugging/frame_cache.c @@ -30,6 +30,7 @@ frame_cache_cleanup(RemoteUnwinderObject *unwinder) return; } for (int i = 0; i < FRAME_CACHE_MAX_THREADS; i++) { + Py_CLEAR(unwinder->frame_cache[i].thread_id_obj); Py_CLEAR(unwinder->frame_cache[i].frame_list); } PyMem_Free(unwinder->frame_cache); @@ -53,6 +54,21 @@ frame_cache_find(RemoteUnwinderObject *unwinder, uint64_t thread_id) return NULL; } +FrameCacheEntry * +frame_cache_find_by_tstate(RemoteUnwinderObject *unwinder, uintptr_t tstate_addr) +{ + if (!unwinder->frame_cache || tstate_addr == 0) { + return NULL; + } + for (int i = 0; i < FRAME_CACHE_MAX_THREADS; i++) { + if (unwinder->frame_cache[i].thread_state_addr == tstate_addr) { + assert(unwinder->frame_cache[i].num_addrs <= FRAME_CACHE_MAX_FRAMES); + return &unwinder->frame_cache[i]; + } + } + return NULL; +} + // Allocate a cache slot for a thread // Returns NULL if cache is full (graceful degradation) static FrameCacheEntry * @@ -127,8 +143,10 @@ frame_cache_invalidate_stale(RemoteUnwinderObject *unwinder, PyObject *result) } if (!found) { // Clear this entry + Py_CLEAR(unwinder->frame_cache[i].thread_id_obj); Py_CLEAR(unwinder->frame_cache[i].frame_list); unwinder->frame_cache[i].thread_id = 0; + unwinder->frame_cache[i].thread_state_addr = 0; unwinder->frame_cache[i].num_addrs = 0; STATS_INC(unwinder, stale_cache_invalidations); } @@ -216,6 +234,7 @@ frame_cache_store( PyObject *frame_list, const uintptr_t *addrs, Py_ssize_t num_addrs, + uintptr_t thread_state_addr, uintptr_t base_frame_addr, uintptr_t last_frame_visited) { @@ -257,6 +276,13 @@ frame_cache_store( return -1; } entry->thread_id = thread_id; + entry->thread_state_addr = thread_state_addr; + if (entry->thread_id_obj == NULL) { + entry->thread_id_obj = PyLong_FromUnsignedLongLong(thread_id); + if (entry->thread_id_obj == NULL) { + return -1; + } + } memcpy(entry->addrs, addrs, num_addrs * sizeof(uintptr_t)); entry->num_addrs = num_addrs; assert(entry->num_addrs == num_addrs); diff --git a/Modules/_remote_debugging/frames.c b/Modules/_remote_debugging/frames.c index bbdfce3f7201d9..1eafd3588db50b 100644 --- a/Modules/_remote_debugging/frames.c +++ b/Modules/_remote_debugging/frames.c @@ -186,30 +186,16 @@ is_frame_valid( return 1; } -int -parse_frame_object( +static int +parse_frame_buffer( RemoteUnwinderObject *unwinder, PyObject** result, - uintptr_t address, + const char *frame, uintptr_t* address_of_code_object, uintptr_t* previous_frame ) { - char frame[SIZEOF_INTERP_FRAME]; *address_of_code_object = 0; - Py_ssize_t bytes_read = _Py_RemoteDebug_PagedReadRemoteMemory( - &unwinder->handle, - address, - SIZEOF_INTERP_FRAME, - frame - ); - if (bytes_read < 0) { - set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read interpreter frame"); - return -1; - } - STATS_INC(unwinder, memory_reads); - STATS_ADD(unwinder, memory_bytes_read, SIZEOF_INTERP_FRAME); - *previous_frame = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.previous); uintptr_t code_object = GET_MEMBER_NO_TAG(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.executable); int frame_valid = is_frame_valid(unwinder, (uintptr_t)frame, code_object); @@ -237,6 +223,31 @@ parse_frame_object( return parse_code_object(unwinder, result, &code_ctx); } +int +parse_frame_object( + RemoteUnwinderObject *unwinder, + PyObject** result, + uintptr_t address, + uintptr_t* address_of_code_object, + uintptr_t* previous_frame +) { + char frame[SIZEOF_INTERP_FRAME]; + Py_ssize_t bytes_read = _Py_RemoteDebug_ReadRemoteMemory( + &unwinder->handle, + address, + SIZEOF_INTERP_FRAME, + frame + ); + if (bytes_read < 0) { + set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read interpreter frame"); + return -1; + } + STATS_INC(unwinder, memory_reads); + STATS_ADD(unwinder, memory_bytes_read, SIZEOF_INTERP_FRAME); + + return parse_frame_buffer(unwinder, result, frame, address_of_code_object, previous_frame); +} + int parse_frame_from_chunks( RemoteUnwinderObject *unwinder, @@ -312,15 +323,32 @@ process_frame_chain( } assert(frame_count <= MAX_FRAMES); - if (parse_frame_from_chunks(unwinder, &frame, frame_addr, &next_frame_addr, &stackpointer, ctx->chunks) < 0) { + if (ctx->chunks && ctx->chunks->count > 0) { + if (parse_frame_from_chunks(unwinder, &frame, frame_addr, &next_frame_addr, &stackpointer, ctx->chunks) == 0) { + goto parsed_frame; + } PyErr_Clear(); + } + { uintptr_t address_of_code_object = 0; - if (parse_frame_object(unwinder, &frame, frame_addr, &address_of_code_object, &next_frame_addr) < 0) { + int parse_result; + if (ctx->prefetched_frame && ctx->prefetched_frame_addr == frame_addr) { + parse_result = parse_frame_buffer( + unwinder, &frame, ctx->prefetched_frame, + &address_of_code_object, &next_frame_addr); + } + else { + parse_result = parse_frame_object( + unwinder, &frame, frame_addr, + &address_of_code_object, &next_frame_addr); + } + if (parse_result < 0) { set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to parse frame object in chain"); return -1; } } +parsed_frame: // Skip first frame if requested (used for cache miss continuation) if (ctx->skip_first_frame && frame_count == 1) { Py_XDECREF(frame); @@ -501,41 +529,37 @@ try_full_cache_hit( PyObject *current_frame = NULL; uintptr_t code_object_addr = 0; uintptr_t previous_frame = 0; - int parse_result = parse_frame_object(unwinder, ¤t_frame, ctx->frame_addr, + int parse_result; + if (ctx->prefetched_frame && ctx->prefetched_frame_addr == ctx->frame_addr) { + parse_result = parse_frame_buffer(unwinder, ¤t_frame, + ctx->prefetched_frame, &code_object_addr, &previous_frame); + } + else { + parse_result = parse_frame_object(unwinder, ¤t_frame, ctx->frame_addr, + &code_object_addr, &previous_frame); + } if (parse_result < 0) { return -1; } - Py_ssize_t cached_size = PyList_GET_SIZE(entry->frame_list); - PyObject *parent_slice = NULL; - if (cached_size > 1) { - parent_slice = PyList_GetSlice(entry->frame_list, 1, cached_size); - if (!parent_slice) { - Py_XDECREF(current_frame); - return -1; - } - } - if (current_frame != NULL) { if (PyList_Append(ctx->frame_info, current_frame) < 0) { Py_DECREF(current_frame); - Py_XDECREF(parent_slice); return -1; } Py_DECREF(current_frame); STATS_ADD(unwinder, frames_read_from_memory, 1); } - if (parent_slice) { - Py_ssize_t cur_size = PyList_GET_SIZE(ctx->frame_info); - int result = PyList_SetSlice(ctx->frame_info, cur_size, cur_size, parent_slice); - Py_DECREF(parent_slice); - if (result < 0) { + Py_ssize_t cached_size = PyList_GET_SIZE(entry->frame_list); + for (Py_ssize_t i = 1; i < cached_size; i++) { + PyObject *cached_frame = PyList_GET_ITEM(entry->frame_list, i); + if (PyList_Append(ctx->frame_info, cached_frame) < 0) { return -1; } - STATS_ADD(unwinder, frames_read_from_cache, cached_size - 1); } + STATS_ADD(unwinder, frames_read_from_cache, cached_size > 1 ? cached_size - 1 : 0); STATS_INC(unwinder, frame_cache_hits); return 1; @@ -606,7 +630,8 @@ collect_frames_with_cache( } if (frame_cache_store(unwinder, thread_id, ctx->frame_info, ctx->frame_addrs, ctx->num_addrs, - ctx->base_frame_addr, ctx->last_frame_visited) < 0) { + ctx->thread_state_addr, ctx->base_frame_addr, + ctx->last_frame_visited) < 0) { return -1; } diff --git a/Modules/_remote_debugging/module.c b/Modules/_remote_debugging/module.c index efdd2e1a2d7b7a..25928b658fd147 100644 --- a/Modules/_remote_debugging/module.c +++ b/Modules/_remote_debugging/module.c @@ -166,6 +166,7 @@ cached_code_metadata_destroy(void *ptr) Py_DECREF(meta->func_name); Py_DECREF(meta->file_name); Py_DECREF(meta->linetable); + Py_XDECREF(meta->last_frame_info); PyMem_RawFree(meta); } @@ -360,6 +361,7 @@ _remote_debugging_RemoteUnwinder___init___impl(RemoteUnwinderObject *self, self->cache_frames = cache_frames; self->collect_stats = stats; self->stale_invalidation_counter = 0; + self->cached_tstate_addr = 0; self->debug = debug; self->only_active_thread = only_active_thread; self->mode = mode; @@ -473,6 +475,46 @@ _remote_debugging_RemoteUnwinder___init___impl(RemoteUnwinderObject *self, return 0; } +static int +read_interp_state_and_maybe_thread_frame( + RemoteUnwinderObject *unwinder, + uintptr_t interpreter_addr, + char *interp_state_buffer, + uintptr_t predicted_tstate_addr, + char *tstate_buffer, + int *tstate_read, + uintptr_t predicted_frame_addr, + char *frame_buffer, + int *frame_read) +{ + *tstate_read = 0; + *frame_read = 0; + if (predicted_tstate_addr != 0) { + size_t tstate_size = (size_t)unwinder->debug_offsets.thread_state.size; + _Py_RemoteReadSegment segments[3] = { + {interpreter_addr, interp_state_buffer, INTERP_STATE_BUFFER_SIZE}, + {predicted_tstate_addr, tstate_buffer, tstate_size}, + {predicted_frame_addr, frame_buffer, SIZEOF_INTERP_FRAME}, + }; + int nsegs = predicted_frame_addr != 0 ? 3 : 2; + Py_ssize_t nread = _Py_RemoteDebug_BatchedReadRemoteMemory( + &unwinder->handle, segments, nsegs); + if (nread >= (Py_ssize_t)INTERP_STATE_BUFFER_SIZE) { + Py_ssize_t with_tstate = (Py_ssize_t)INTERP_STATE_BUFFER_SIZE + + (Py_ssize_t)tstate_size; + *tstate_read = nread >= with_tstate; + *frame_read = nsegs == 3 + && nread == with_tstate + (Py_ssize_t)SIZEOF_INTERP_FRAME; + return 0; + } + } + return _Py_RemoteDebug_ReadRemoteMemory( + &unwinder->handle, + interpreter_addr, + INTERP_STATE_BUFFER_SIZE, + interp_state_buffer); +} + /*[clinic input] @permit_long_docstring_body @critical_section @@ -537,11 +579,29 @@ _remote_debugging_RemoteUnwinder_get_stack_trace_impl(RemoteUnwinderObject *self while (current_interpreter != 0) { // Read interpreter state to get the interpreter ID char interp_state_buffer[INTERP_STATE_BUFFER_SIZE]; - if (_Py_RemoteDebug_PagedReadRemoteMemory( - &self->handle, + char prefetched_tstate[SIZEOF_THREAD_STATE]; + char prefetched_frame[SIZEOF_INTERP_FRAME]; + int have_prefetched_tstate = 0; + int have_prefetched_frame = 0; + uintptr_t predicted_tstate_addr = self->cache_frames ? self->cached_tstate_addr : 0; + uintptr_t predicted_frame_addr = 0; + if (predicted_tstate_addr != 0) { + FrameCacheEntry *entry = frame_cache_find_by_tstate(self, predicted_tstate_addr); + if (entry && entry->num_addrs > 0) { + predicted_frame_addr = entry->addrs[0]; + } + } + + if (read_interp_state_and_maybe_thread_frame( + self, current_interpreter, - INTERP_STATE_BUFFER_SIZE, - interp_state_buffer) < 0) { + interp_state_buffer, + predicted_tstate_addr, + prefetched_tstate, + &have_prefetched_tstate, + predicted_frame_addr, + prefetched_frame, + &have_prefetched_frame) < 0) { set_exception_cause(self, PyExc_RuntimeError, "Failed to read interpreter state buffer"); Py_CLEAR(result); goto exit; @@ -611,6 +671,9 @@ _remote_debugging_RemoteUnwinder_get_stack_trace_impl(RemoteUnwinderObject *self // Target specific thread (only process first interpreter) current_tstate = self->tstate_addr; } + if (current_tstate != 0) { + self->cached_tstate_addr = current_tstate; + } // Acquire main thread state information uintptr_t main_thread_tstate = GET_MEMBER(uintptr_t, interp_state_buffer, @@ -621,7 +684,11 @@ _remote_debugging_RemoteUnwinder_get_stack_trace_impl(RemoteUnwinderObject *self PyObject* frame_info = unwind_stack_for_thread(self, ¤t_tstate, gil_holder_tstate, gc_frame, - main_thread_tstate); + main_thread_tstate, + have_prefetched_tstate ? prefetched_tstate : NULL, + predicted_tstate_addr, + have_prefetched_frame ? prefetched_frame : NULL, + predicted_frame_addr); if (!frame_info) { // Check if this was an intentional skip due to mode-based filtering if ((self->mode == PROFILING_MODE_CPU || self->mode == PROFILING_MODE_GIL || diff --git a/Modules/_remote_debugging/threads.c b/Modules/_remote_debugging/threads.c index 4daa5e5f92bcd9..3e3164094480ea 100644 --- a/Modules/_remote_debugging/threads.c +++ b/Modules/_remote_debugging/threads.c @@ -289,13 +289,44 @@ typedef struct { unsigned int :24; } _thread_status; +static int +read_thread_state_and_maybe_frame( + RemoteUnwinderObject *unwinder, + uintptr_t tstate_addr, + size_t tstate_size, + char *tstate_buffer, + uintptr_t predicted_frame_addr, + char *frame_buffer, + int *frame_read) +{ + *frame_read = 0; + if (predicted_frame_addr != 0) { + _Py_RemoteReadSegment segments[2] = { + {tstate_addr, tstate_buffer, tstate_size}, + {predicted_frame_addr, frame_buffer, SIZEOF_INTERP_FRAME}, + }; + Py_ssize_t nread = _Py_RemoteDebug_BatchedReadRemoteMemory( + &unwinder->handle, segments, 2); + if (nread >= (Py_ssize_t)tstate_size) { + *frame_read = nread == (Py_ssize_t)(tstate_size + SIZEOF_INTERP_FRAME); + return 0; + } + } + return _Py_RemoteDebug_ReadRemoteMemory( + &unwinder->handle, tstate_addr, tstate_size, tstate_buffer); +} + PyObject* unwind_stack_for_thread( RemoteUnwinderObject *unwinder, uintptr_t *current_tstate, uintptr_t gil_holder_tstate, uintptr_t gc_frame, - uintptr_t main_thread_tstate + uintptr_t main_thread_tstate, + const char *prefetched_tstate, + uintptr_t prefetched_tstate_addr, + const char *prefetched_frame, + uintptr_t prefetched_frame_addr ) { PyObject *frame_info = NULL; PyObject *thread_id = NULL; @@ -303,14 +334,57 @@ unwind_stack_for_thread( StackChunkList chunks = {0}; char ts[SIZEOF_THREAD_STATE]; - int bytes_read = _Py_RemoteDebug_PagedReadRemoteMemory( - &unwinder->handle, *current_tstate, (size_t)unwinder->debug_offsets.thread_state.size, ts); - if (bytes_read < 0) { - set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read thread state"); - goto error; + char local_prefetched_frame[SIZEOF_INTERP_FRAME]; + const char *prefetched_frame_for_ctx = NULL; + int have_prefetched_frame = 0; + uintptr_t predicted_frame_addr = 0; + if (prefetched_tstate && prefetched_tstate_addr == *current_tstate) { + memcpy(ts, prefetched_tstate, (size_t)unwinder->debug_offsets.thread_state.size); + if (prefetched_frame && prefetched_frame_addr != 0) { + have_prefetched_frame = 1; + prefetched_frame_for_ctx = prefetched_frame; + predicted_frame_addr = prefetched_frame_addr; + } + } + else if (unwinder->cache_frames) { + FrameCacheEntry *entry = frame_cache_find_by_tstate(unwinder, *current_tstate); + if (entry && entry->num_addrs > 0) { + predicted_frame_addr = entry->addrs[0]; + } + + int bytes_read = read_thread_state_and_maybe_frame( + unwinder, + *current_tstate, + (size_t)unwinder->debug_offsets.thread_state.size, + ts, + predicted_frame_addr, + local_prefetched_frame, + &have_prefetched_frame); + if (bytes_read < 0) { + set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read thread state"); + goto error; + } + if (have_prefetched_frame) { + prefetched_frame_for_ctx = local_prefetched_frame; + } + } + else { + int bytes_read = _Py_RemoteDebug_ReadRemoteMemory( + &unwinder->handle, + *current_tstate, + (size_t)unwinder->debug_offsets.thread_state.size, + ts); + if (bytes_read < 0) { + set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read thread state"); + goto error; + } } STATS_INC(unwinder, memory_reads); STATS_ADD(unwinder, memory_bytes_read, unwinder->debug_offsets.thread_state.size); + if (have_prefetched_frame) { + STATS_INC(unwinder, memory_reads); + STATS_ADD(unwinder, memory_bytes_read, SIZEOF_INTERP_FRAME); + } long tid = GET_MEMBER(long, ts, unwinder->debug_offsets.thread_state.native_thread_id); @@ -432,9 +506,12 @@ unwind_stack_for_thread( uintptr_t addrs[FRAME_CACHE_MAX_FRAMES]; FrameWalkContext ctx = { .frame_addr = frame_addr, + .thread_state_addr = *current_tstate, .base_frame_addr = base_frame_addr, .gc_frame = gc_frame, .chunks = &chunks, + .prefetched_frame = have_prefetched_frame ? prefetched_frame_for_ctx : NULL, + .prefetched_frame_addr = predicted_frame_addr, .frame_info = frame_info, .frame_addrs = addrs, .num_addrs = 0, @@ -469,10 +546,18 @@ unwind_stack_for_thread( *current_tstate = GET_MEMBER(uintptr_t, ts, unwinder->debug_offsets.thread_state.next); - thread_id = PyLong_FromLongLong(tid); + if (unwinder->cache_frames) { + FrameCacheEntry *entry = frame_cache_find(unwinder, (uint64_t)tid); + if (entry && entry->thread_id_obj) { + thread_id = Py_NewRef(entry->thread_id_obj); + } + } if (thread_id == NULL) { - set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to create thread ID"); - goto error; + thread_id = PyLong_FromLongLong(tid); + if (thread_id == NULL) { + set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to create thread ID"); + goto error; + } } RemoteDebuggingState *state = RemoteDebugging_GetStateFromObject((PyObject*)unwinder); diff --git a/Python/remote_debug.h b/Python/remote_debug.h index 6c089a834dcd40..7b2c4f3bcb8077 100644 --- a/Python/remote_debug.h +++ b/Python/remote_debug.h @@ -147,6 +147,7 @@ typedef struct { int memfd; #endif page_cache_entry_t pages[MAX_PAGES]; + int page_cache_count; Py_ssize_t page_size; } proc_handle_t; @@ -185,14 +186,16 @@ _Py_RemoteDebug_FreePageCache(proc_handle_t *handle) handle->pages[i].data = NULL; handle->pages[i].valid = 0; } + handle->page_cache_count = 0; } UNUSED static void _Py_RemoteDebug_ClearCache(proc_handle_t *handle) { - for (int i = 0; i < MAX_PAGES; i++) { + for (int i = 0; i < handle->page_cache_count; i++) { handle->pages[i].valid = 0; } + handle->page_cache_count = 0; } #if defined(__APPLE__) && defined(TARGET_OS_OSX) && TARGET_OS_OSX @@ -222,6 +225,7 @@ _Py_RemoteDebug_InitProcHandle(proc_handle_t *handle, pid_t pid) { handle->memfd = -1; #endif handle->page_size = get_page_size(); + handle->page_cache_count = 0; for (int i = 0; i < MAX_PAGES; i++) { handle->pages[i].data = NULL; handle->pages[i].valid = 0; @@ -1287,8 +1291,9 @@ _Py_RemoteDebug_PagedReadRemoteMemory(proc_handle_t *handle, return _Py_RemoteDebug_ReadRemoteMemory(handle, addr, size, out); } - // Search for valid cached page - for (int i = 0; i < MAX_PAGES; i++) { + // Search only the pages used since the last clear. The cache is cleared + // between profiler samples, so entries are packed at the front. + for (int i = 0; i < handle->page_cache_count; 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); @@ -1296,33 +1301,31 @@ _Py_RemoteDebug_PagedReadRemoteMemory(proc_handle_t *handle, } } - // Find reusable slot - for (int i = 0; i < MAX_PAGES; i++) { - page_cache_entry_t *entry = &handle->pages[i]; - if (!entry->valid) { + if (handle->page_cache_count < MAX_PAGES) { + page_cache_entry_t *entry = &handle->pages[handle->page_cache_count]; + if (entry->data == NULL) { + entry->data = PyMem_RawMalloc(page_size); if (entry->data == NULL) { - entry->data = PyMem_RawMalloc(page_size); - if (entry->data == NULL) { - PyErr_NoMemory(); - _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 amount as a fallback - PyErr_Clear(); - goto fallback; + PyErr_NoMemory(); + _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; } + } - entry->page_addr = page_base; - entry->valid = 1; - memcpy(out, entry->data + offset_in_page, size); - return 0; + if (_Py_RemoteDebug_ReadRemoteMemory(handle, page_base, page_size, entry->data) < 0) { + // Try to just copy the exact amount as a fallback + PyErr_Clear(); + goto fallback; } + + entry->page_addr = page_base; + entry->valid = 1; + handle->page_cache_count++; + memcpy(out, entry->data + offset_in_page, size); + return 0; } fallback: @@ -1330,6 +1333,49 @@ _Py_RemoteDebug_PagedReadRemoteMemory(proc_handle_t *handle, return _Py_RemoteDebug_ReadRemoteMemory(handle, addr, size, out); } +typedef struct { + uintptr_t remote_addr; + void *local_buf; + size_t size; +} _Py_RemoteReadSegment; + +#define _PY_REMOTE_DEBUG_MAX_BATCHED_SEGMENTS 4 + +// Batched read of multiple remote regions in a single syscall when supported. +// Returns total bytes read (>= 0) on success, -1 if batched reads are +// unavailable or the syscall failed. Callers compare the return value against +// cumulative segment sizes to determine which segments were fully populated. +UNUSED static Py_ssize_t +_Py_RemoteDebug_BatchedReadRemoteMemory( + proc_handle_t *handle, + const _Py_RemoteReadSegment *segments, + int nsegs) +{ +#if defined(__linux__) && HAVE_PROCESS_VM_READV + if (handle->memfd == -1 + && nsegs > 0 + && nsegs <= _PY_REMOTE_DEBUG_MAX_BATCHED_SEGMENTS) { + struct iovec local[_PY_REMOTE_DEBUG_MAX_BATCHED_SEGMENTS]; + struct iovec remote[_PY_REMOTE_DEBUG_MAX_BATCHED_SEGMENTS]; + for (int i = 0; i < nsegs; i++) { + local[i].iov_base = segments[i].local_buf; + local[i].iov_len = segments[i].size; + remote[i].iov_base = (void *)segments[i].remote_addr; + remote[i].iov_len = segments[i].size; + } + ssize_t nread = process_vm_readv(handle->pid, local, nsegs, remote, nsegs, 0); + if (nread >= 0) { + return (Py_ssize_t)nread; + } + } +#else + (void)handle; + (void)segments; + (void)nsegs; +#endif + return -1; +} + UNUSED static int _Py_RemoteDebug_ReadDebugOffsets( proc_handle_t *handle,