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extmod/modselect: Add optimisation to use system poll when possible. 

A previous commit removed the unix-specific select module implementation
and made unix use the common one.

This commit adds an optimisation so that the system poll function is used
when polling objects that have a file descriptor.  With this optimisation
enabled, if code registers both file-descriptor-based objects, and non-
file-descriptor-based objects with select.poll() then the following occurs:

- the system poll is called for all file-descriptor-based objects with a
  timeout of 1ms

- then the bare-metal polling implementation is used for remaining objects,
  which calls into their ioctl method (which can be in C or Python)

In the case where all objects have file descriptors, the system poll is
called with the full timeout requested by the caller.  That makes it as
efficient as possible in the case everything has a file descriptor.

Benefits of this approach:

- all ports use the same select module implementation

- the unix port now supports polling of all objects and matches bare metal
  implementations

- it's still efficient for existing cases where only files and sockets are
  polled (on unix)

- the bare metal implementation does not change

- polling of SSL objects will now work on unix by calling in to the ioctl
  method on SSL objects (this is required for asyncio ssl support)

Note that extmod/vfs_posix_file.c has poll disable when the optimisation is
enabled, because the code is not reachable when the optimisation is used.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George 2023-08-01 12:39:39 +10:00
parent ebc6556346
commit ef71028f77
4 changed files with 284 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

308
extmod/modselect.c
View File

@ -35,6 +35,29 @@
#if MICROPY_PY_SELECT
#if MICROPY_PY_SELECT_SELECT && MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
#error "select.select is not supported with MICROPY_PY_SELECT_POSIX_OPTIMISATIONS"
#endif
#if MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
#include <poll.h>
#if !((MP_STREAM_POLL_RD) == (POLLIN) && \
(MP_STREAM_POLL_WR) == (POLLOUT) && \
(MP_STREAM_POLL_ERR) == (POLLERR) && \
(MP_STREAM_POLL_HUP) == (POLLHUP) && \
(MP_STREAM_POLL_NVAL) == (POLLNVAL))
#error "With MICROPY_PY_SELECT_POSIX_OPTIMISATIONS enabled, POLL constants must match"
#endif
// When non-file-descriptor objects are on the list to be polled (the polling of
// which involves repeatedly calling ioctl(MP_STREAM_POLL)), this variable sets
// the period between polling these objects.
#define MICROPY_PY_SELECT_IOCTL_CALL_PERIOD_MS (1)
#endif
// Flags for poll()
#define FLAG_ONESHOT (1)
@ -42,18 +65,42 @@
typedef struct _poll_obj_t {
mp_obj_t obj;
mp_uint_t (*ioctl)(mp_obj_t obj, mp_uint_t request, uintptr_t arg, int *errcode);
mp_uint_t flags;
mp_uint_t flags_ret;
#if MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
// If the pollable object has an associated file descriptor, then pollfd points to an entry
// in poll_set_t::pollfds, and the events/revents fields for this object are stored in the
// pollfd entry (and the nonfd_* members are unused).
// Otherwise the object is a non-file-descriptor object and pollfd==NULL, and the events/
// revents fields are stored in the nonfd_* members (which are named as such so that code
// doesn't accidentally mix the use of these members when this optimisation is used).
struct pollfd *pollfd;
uint16_t nonfd_events;
uint16_t nonfd_revents;
#else
mp_uint_t events;
mp_uint_t revents;
#endif
} poll_obj_t;
// A set of pollable objects.
typedef struct _poll_set_t {
// Map containing a dict with key=object to poll, value=its corresponding poll_obj_t.
mp_map_t map;
#if MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
// Array of pollfd entries for objects that have a file descriptor.
unsigned short alloc;
unsigned short len;
struct pollfd *pollfds;
#endif
} poll_set_t;
STATIC void poll_set_init(poll_set_t *poll_set, size_t n) {
mp_map_init(&poll_set->map, n);
#if MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
poll_set->alloc = 0;
poll_set->len = 0;
poll_set->pollfds = NULL;
#endif
}
#if MICROPY_PY_SELECT_SELECT
@ -62,25 +109,141 @@ STATIC void poll_set_deinit(poll_set_t *poll_set) {
}
#endif
STATIC void poll_set_add_obj(poll_set_t *poll_set, const mp_obj_t *obj, mp_uint_t obj_len, mp_uint_t flags, bool or_flags) {
#if MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
STATIC mp_uint_t poll_obj_get_events(poll_obj_t *poll_obj) {
assert(poll_obj->pollfd == NULL);
return poll_obj->nonfd_events;
}
STATIC void poll_obj_set_events(poll_obj_t *poll_obj, mp_uint_t events) {
if (poll_obj->pollfd != NULL) {
poll_obj->pollfd->events = events;
} else {
poll_obj->nonfd_events = events;
}
}
STATIC mp_uint_t poll_obj_get_revents(poll_obj_t *poll_obj) {
if (poll_obj->pollfd != NULL) {
return poll_obj->pollfd->revents;
} else {
return poll_obj->nonfd_revents;
}
}
STATIC void poll_obj_set_revents(poll_obj_t *poll_obj, mp_uint_t revents) {
if (poll_obj->pollfd != NULL) {
poll_obj->pollfd->revents = revents;
} else {
poll_obj->nonfd_revents = revents;
}
}
STATIC struct pollfd *poll_set_add_fd(poll_set_t *poll_set, int fd) {
struct pollfd *free_slot = NULL;
for (unsigned int i = 0; i < poll_set->len; ++i) {
struct pollfd *slot = &poll_set->pollfds[i];
if (slot->fd == -1) {
free_slot = slot;
break;
}
}
if (free_slot == NULL) {
if (poll_set->len >= poll_set->alloc) {
poll_set->pollfds = m_renew(struct pollfd, poll_set->pollfds, poll_set->alloc, poll_set->alloc + 4);
poll_set->alloc += 4;
}
free_slot = &poll_set->pollfds[poll_set->len++];
}
free_slot->fd = fd;
return free_slot;
}
static inline bool poll_set_all_are_fds(poll_set_t *poll_set) {
return poll_set->map.used == poll_set->len;
}
#else
static inline mp_uint_t poll_obj_get_events(poll_obj_t *poll_obj) {
return poll_obj->events;
}
static inline void poll_obj_set_events(poll_obj_t *poll_obj, mp_uint_t events) {
poll_obj->events = events;
}
static inline mp_uint_t poll_obj_get_revents(poll_obj_t *poll_obj) {
return poll_obj->revents;
}
static inline void poll_obj_set_revents(poll_obj_t *poll_obj, mp_uint_t revents) {
poll_obj->revents = revents;
}
#endif
STATIC void poll_set_add_obj(poll_set_t *poll_set, const mp_obj_t *obj, mp_uint_t obj_len, mp_uint_t events, bool or_events) {
for (mp_uint_t i = 0; i < obj_len; i++) {
mp_map_elem_t *elem = mp_map_lookup(&poll_set->map, mp_obj_id(obj[i]), MP_MAP_LOOKUP_ADD_IF_NOT_FOUND);
if (elem->value == MP_OBJ_NULL) {
// object not found; get its ioctl and add it to the poll list
const mp_stream_p_t *stream_p = mp_get_stream_raise(obj[i], MP_STREAM_OP_IOCTL);
// If an exception is raised below when adding the new object then the map entry for that
// object remains unpopulated, and methods like poll() may crash. This case is not handled.
poll_obj_t *poll_obj = m_new_obj(poll_obj_t);
poll_obj->obj = obj[i];
#if MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
int fd = -1;
if (mp_obj_is_int(obj[i])) {
// A file descriptor integer passed in as the object, so use it directly.
fd = mp_obj_get_int(obj[i]);
if (fd < 0) {
mp_raise_ValueError(NULL);
}
poll_obj->ioctl = NULL;
} else {
// An object passed in. Check if it has a file descriptor.
const mp_stream_p_t *stream_p = mp_get_stream_raise(obj[i], MP_STREAM_OP_IOCTL);
poll_obj->ioctl = stream_p->ioctl;
int err;
mp_uint_t res = stream_p->ioctl(obj[i], MP_STREAM_GET_FILENO, 0, &err);
if (res != MP_STREAM_ERROR) {
fd = res;
}
}
if (fd >= 0) {
// Object has a file descriptor so add it to pollfds.
poll_obj->pollfd = poll_set_add_fd(poll_set, fd);
} else {
// Object doesn't have a file descriptor.
poll_obj->pollfd = NULL;
}
#else
const mp_stream_p_t *stream_p = mp_get_stream_raise(obj[i], MP_STREAM_OP_IOCTL);
poll_obj->ioctl = stream_p->ioctl;
poll_obj->flags = flags;
poll_obj->flags_ret = 0;
#endif
poll_obj_set_events(poll_obj, events);
poll_obj_set_revents(poll_obj, 0);
elem->value = MP_OBJ_FROM_PTR(poll_obj);
} else {
// object exists; update its flags
if (or_flags) {
((poll_obj_t *)MP_OBJ_TO_PTR(elem->value))->flags |= flags;
} else {
((poll_obj_t *)MP_OBJ_TO_PTR(elem->value))->flags = flags;
// object exists; update its events
poll_obj_t *poll_obj = (poll_obj_t *)MP_OBJ_TO_PTR(elem->value);
#if MICROPY_PY_SELECT_SELECT
if (or_events) {
events |= poll_obj_get_events(poll_obj);
}
#else
(void)or_events;
#endif
poll_obj_set_events(poll_obj, events);
}
}
}
@ -94,9 +257,17 @@ STATIC mp_uint_t poll_set_poll_once(poll_set_t *poll_set, size_t *rwx_num) {
}
poll_obj_t *poll_obj = MP_OBJ_TO_PTR(poll_set->map.table[i].value);
#if MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
if (poll_obj->pollfd != NULL) {
// Object has file descriptor so will be polled separately by poll().
continue;
}
#endif
int errcode;
mp_int_t ret = poll_obj->ioctl(poll_obj->obj, MP_STREAM_POLL, poll_obj->flags, &errcode);
poll_obj->flags_ret = ret;
mp_int_t ret = poll_obj->ioctl(poll_obj->obj, MP_STREAM_POLL, poll_obj_get_events(poll_obj), &errcode);
poll_obj_set_revents(poll_obj, ret);
if (ret == -1) {
// error doing ioctl
@ -106,6 +277,7 @@ STATIC mp_uint_t poll_set_poll_once(poll_set_t *poll_set, size_t *rwx_num) {
if (ret != 0) {
// object is ready
n_ready += 1;
#if MICROPY_PY_SELECT_SELECT
if (rwx_num != NULL) {
if (ret & MP_STREAM_POLL_RD) {
rwx_num[0] += 1;
@ -117,21 +289,80 @@ STATIC mp_uint_t poll_set_poll_once(poll_set_t *poll_set, size_t *rwx_num) {
rwx_num[2] += 1;
}
}
#else
(void)rwx_num;
#endif
}
}
return n_ready;
}
STATIC mp_uint_t poll_set_poll_until_ready_or_timeout(poll_set_t *poll_set, size_t *rwx_num, mp_uint_t timeout) {
mp_uint_t start_tick = mp_hal_ticks_ms();
mp_uint_t start_ticks = mp_hal_ticks_ms();
#if MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
for (;;) {
MP_THREAD_GIL_EXIT();
// Compute the timeout.
int t = MICROPY_PY_SELECT_IOCTL_CALL_PERIOD_MS;
if (poll_set_all_are_fds(poll_set)) {
// All our pollables are file descriptors, so we can use a blocking
// poll and let it (the underlying system) handle the timeout.
if (timeout == (mp_uint_t)-1) {
t = -1;
} else {
mp_uint_t delta = mp_hal_ticks_ms() - start_ticks;
if (delta >= timeout) {
t = 0;
} else {
t = timeout - delta;
}
}
}
// Call system poll for those objects that have a file descriptor.
int n_ready = poll(poll_set->pollfds, poll_set->len, t);
MP_THREAD_GIL_ENTER();
// The call to poll() may have been interrupted, but per PEP 475 we must retry if the
// signal is EINTR (this implements a special case of calling MP_HAL_RETRY_SYSCALL()).
if (n_ready == -1) {
int err = errno;
if (err != EINTR) {
mp_raise_OSError(err);
}
n_ready = 0;
}
// Explicitly poll any objects that do not have a file descriptor.
if (!poll_set_all_are_fds(poll_set)) {
n_ready += poll_set_poll_once(poll_set, rwx_num);
}
// Return if an object is ready, or if the timeout expired.
if (n_ready > 0 || (timeout != (mp_uint_t)-1 && mp_hal_ticks_ms() - start_ticks >= timeout)) {
return n_ready;
}
// This would be MICROPY_EVENT_POLL_HOOK but the call to poll() above already includes a delay.
mp_handle_pending(true);
}
#else
for (;;) {
// poll the objects
mp_uint_t n_ready = poll_set_poll_once(poll_set, rwx_num);
if (n_ready > 0 || (timeout != (mp_uint_t)-1 && mp_hal_ticks_ms() - start_tick >= timeout)) {
if (n_ready > 0 || (timeout != (mp_uint_t)-1 && mp_hal_ticks_ms() - start_ticks >= timeout)) {
return n_ready;
}
MICROPY_EVENT_POLL_HOOK
}
#endif
}
#if MICROPY_PY_SELECT_SELECT
@ -181,13 +412,13 @@ STATIC mp_obj_t select_select(size_t n_args, const mp_obj_t *args) {
continue;
}
poll_obj_t *poll_obj = MP_OBJ_TO_PTR(poll_set.map.table[i].value);
if (poll_obj->flags_ret & MP_STREAM_POLL_RD) {
if (poll_obj->revents & MP_STREAM_POLL_RD) {
((mp_obj_list_t *)MP_OBJ_TO_PTR(list_array[0]))->items[rwx_len[0]++] = poll_obj->obj;
}
if (poll_obj->flags_ret & MP_STREAM_POLL_WR) {
if (poll_obj->revents & MP_STREAM_POLL_WR) {
((mp_obj_list_t *)MP_OBJ_TO_PTR(list_array[1]))->items[rwx_len[1]++] = poll_obj->obj;
}
if ((poll_obj->flags_ret & ~(MP_STREAM_POLL_RD | MP_STREAM_POLL_WR)) != 0) {
if ((poll_obj->revents & ~(MP_STREAM_POLL_RD | MP_STREAM_POLL_WR)) != 0) {
((mp_obj_list_t *)MP_OBJ_TO_PTR(list_array[2]))->items[rwx_len[2]++] = poll_obj->obj;
}
}
@ -210,13 +441,13 @@ typedef struct _mp_obj_poll_t {
// register(obj[, eventmask])
STATIC mp_obj_t poll_register(size_t n_args, const mp_obj_t *args) {
mp_obj_poll_t *self = MP_OBJ_TO_PTR(args[0]);
mp_uint_t flags;
mp_uint_t events;
if (n_args == 3) {
flags = mp_obj_get_int(args[2]);
events = mp_obj_get_int(args[2]);
} else {
flags = MP_STREAM_POLL_RD | MP_STREAM_POLL_WR;
events = MP_STREAM_POLL_RD | MP_STREAM_POLL_WR;
}
poll_set_add_obj(&self->poll_set, &args[1], 1, flags, false);
poll_set_add_obj(&self->poll_set, &args[1], 1, events, false);
return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(poll_register_obj, 2, 3, poll_register);
@ -224,7 +455,20 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(poll_register_obj, 2, 3, poll_register);
// unregister(obj)
STATIC mp_obj_t poll_unregister(mp_obj_t self_in, mp_obj_t obj_in) {
mp_obj_poll_t *self = MP_OBJ_TO_PTR(self_in);
mp_map_lookup(&self->poll_set.map, mp_obj_id(obj_in), MP_MAP_LOOKUP_REMOVE_IF_FOUND);
mp_map_elem_t *elem = mp_map_lookup(&self->poll_set.map, mp_obj_id(obj_in), MP_MAP_LOOKUP_REMOVE_IF_FOUND);
#if MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
if (elem != NULL) {
poll_obj_t *poll_obj = (poll_obj_t *)MP_OBJ_TO_PTR(elem->value);
if (poll_obj->pollfd != NULL) {
poll_obj->pollfd->fd = -1;
}
elem->value = MP_OBJ_NULL;
}
#else
(void)elem;
#endif
// TODO raise KeyError if obj didn't exist in map
return mp_const_none;
}
@ -237,7 +481,7 @@ STATIC mp_obj_t poll_modify(mp_obj_t self_in, mp_obj_t obj_in, mp_obj_t eventmas
if (elem == NULL) {
mp_raise_OSError(MP_ENOENT);
}
((poll_obj_t *)MP_OBJ_TO_PTR(elem->value))->flags = mp_obj_get_int(eventmask_in);
poll_obj_set_events((poll_obj_t *)MP_OBJ_TO_PTR(elem->value), mp_obj_get_int(eventmask_in));
return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_3(poll_modify_obj, poll_modify);
@ -277,12 +521,12 @@ STATIC mp_obj_t poll_poll(size_t n_args, const mp_obj_t *args) {
continue;
}
poll_obj_t *poll_obj = MP_OBJ_TO_PTR(self->poll_set.map.table[i].value);
if (poll_obj->flags_ret != 0) {
mp_obj_t tuple[2] = {poll_obj->obj, MP_OBJ_NEW_SMALL_INT(poll_obj->flags_ret)};
if (poll_obj_get_revents(poll_obj) != 0) {
mp_obj_t tuple[2] = {poll_obj->obj, MP_OBJ_NEW_SMALL_INT(poll_obj_get_revents(poll_obj))};
ret_list->items[n_ready++] = mp_obj_new_tuple(2, tuple);
if (self->flags & FLAG_ONESHOT) {
// Don't poll next time, until new event flags will be set explicitly
poll_obj->flags = 0;
// Don't poll next time, until new event mask will be set explicitly
poll_obj_set_events(poll_obj, 0);
}
}
}
@ -320,13 +564,13 @@ STATIC mp_obj_t poll_iternext(mp_obj_t self_in) {
continue;
}
poll_obj_t *poll_obj = MP_OBJ_TO_PTR(self->poll_set.map.table[i].value);
if (poll_obj->flags_ret != 0) {
if (poll_obj_get_revents(poll_obj) != 0) {
mp_obj_tuple_t *t = MP_OBJ_TO_PTR(self->ret_tuple);
t->items[0] = poll_obj->obj;
t->items[1] = MP_OBJ_NEW_SMALL_INT(poll_obj->flags_ret);
t->items[1] = MP_OBJ_NEW_SMALL_INT(poll_obj_get_revents(poll_obj));
if (self->flags & FLAG_ONESHOT) {
// Don't poll next time, until new event flags will be set explicitly
poll_obj->flags = 0;
// Don't poll next time, until new event mask will be set explicitly
poll_obj_set_events(poll_obj, 0);
}
return MP_OBJ_FROM_PTR(t);
}

2
extmod/vfs_posix_file.c
View File

@ -188,7 +188,7 @@ STATIC mp_uint_t vfs_posix_file_ioctl(mp_obj_t o_in, mp_uint_t request, uintptr_
return 0;
case MP_STREAM_GET_FILENO:
return o->fd;
#if MICROPY_PY_SELECT
#if MICROPY_PY_SELECT && !MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
case MP_STREAM_POLL: {
#ifdef _WIN32
mp_raise_NotImplementedError(MP_ERROR_TEXT("poll on file not available on win32"));

1
ports/unix/variants/mpconfigvariant_common.h
View File

@ -107,6 +107,7 @@
#endif
// The "select" module is enabled by default, but disable select.select().
#define MICROPY_PY_SELECT_POSIX_OPTIMISATIONS (1)
#define MICROPY_PY_SELECT_SELECT (0)
// Enable the "websocket" module.

7
py/mpconfig.h
View File

@ -1485,11 +1485,16 @@ typedef double mp_float_t;
#define MICROPY_PY_ERRNO_ERRORCODE (1)
#endif
// Whether to provide "select" module (baremetal implementation)
// Whether to provide "select" module
#ifndef MICROPY_PY_SELECT
#define MICROPY_PY_SELECT (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_EXTRA_FEATURES)
#endif
// Whether to enable POSIX optimisations in the "select" module (requires system poll)
#ifndef MICROPY_PY_SELECT_POSIX_OPTIMISATIONS
#define MICROPY_PY_SELECT_POSIX_OPTIMISATIONS (0)
#endif
// Whether to enable the select() function in the "select" module (baremetal
// implementation). This is present for compatibility but can be disabled to
// save space.