* GNU GPL, version 2 or (at your option) any later version.
*/
+#include "qemu/osdep.h"
#include "qemu-common.h"
#include "block/block.h"
#include "qemu/queue.h"
#include "qemu/sockets.h"
+#ifdef CONFIG_EPOLL_CREATE1
+#include <sys/epoll.h>
+#endif
struct AioHandler
{
IOHandler *io_read;
IOHandler *io_write;
int deleted;
- int pollfds_idx;
void *opaque;
+ bool is_external;
QLIST_ENTRY(AioHandler) node;
};
+#ifdef CONFIG_EPOLL_CREATE1
+
+/* The fd number threashold to switch to epoll */
+#define EPOLL_ENABLE_THRESHOLD 64
+
+static void aio_epoll_disable(AioContext *ctx)
+{
+ ctx->epoll_available = false;
+ if (!ctx->epoll_enabled) {
+ return;
+ }
+ ctx->epoll_enabled = false;
+ close(ctx->epollfd);
+}
+
+static inline int epoll_events_from_pfd(int pfd_events)
+{
+ return (pfd_events & G_IO_IN ? EPOLLIN : 0) |
+ (pfd_events & G_IO_OUT ? EPOLLOUT : 0) |
+ (pfd_events & G_IO_HUP ? EPOLLHUP : 0) |
+ (pfd_events & G_IO_ERR ? EPOLLERR : 0);
+}
+
+static bool aio_epoll_try_enable(AioContext *ctx)
+{
+ AioHandler *node;
+ struct epoll_event event;
+
+ QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+ int r;
+ if (node->deleted || !node->pfd.events) {
+ continue;
+ }
+ event.events = epoll_events_from_pfd(node->pfd.events);
+ event.data.ptr = node;
+ r = epoll_ctl(ctx->epollfd, EPOLL_CTL_ADD, node->pfd.fd, &event);
+ if (r) {
+ return false;
+ }
+ }
+ ctx->epoll_enabled = true;
+ return true;
+}
+
+static void aio_epoll_update(AioContext *ctx, AioHandler *node, bool is_new)
+{
+ struct epoll_event event;
+ int r;
+
+ if (!ctx->epoll_enabled) {
+ return;
+ }
+ if (!node->pfd.events) {
+ r = epoll_ctl(ctx->epollfd, EPOLL_CTL_DEL, node->pfd.fd, &event);
+ if (r) {
+ aio_epoll_disable(ctx);
+ }
+ } else {
+ event.data.ptr = node;
+ event.events = epoll_events_from_pfd(node->pfd.events);
+ if (is_new) {
+ r = epoll_ctl(ctx->epollfd, EPOLL_CTL_ADD, node->pfd.fd, &event);
+ if (r) {
+ aio_epoll_disable(ctx);
+ }
+ } else {
+ r = epoll_ctl(ctx->epollfd, EPOLL_CTL_MOD, node->pfd.fd, &event);
+ if (r) {
+ aio_epoll_disable(ctx);
+ }
+ }
+ }
+}
+
+static int aio_epoll(AioContext *ctx, GPollFD *pfds,
+ unsigned npfd, int64_t timeout)
+{
+ AioHandler *node;
+ int i, ret = 0;
+ struct epoll_event events[128];
+
+ assert(npfd == 1);
+ assert(pfds[0].fd == ctx->epollfd);
+ if (timeout > 0) {
+ ret = qemu_poll_ns(pfds, npfd, timeout);
+ }
+ if (timeout <= 0 || ret > 0) {
+ ret = epoll_wait(ctx->epollfd, events,
+ sizeof(events) / sizeof(events[0]),
+ timeout);
+ if (ret <= 0) {
+ goto out;
+ }
+ for (i = 0; i < ret; i++) {
+ int ev = events[i].events;
+ node = events[i].data.ptr;
+ node->pfd.revents = (ev & EPOLLIN ? G_IO_IN : 0) |
+ (ev & EPOLLOUT ? G_IO_OUT : 0) |
+ (ev & EPOLLHUP ? G_IO_HUP : 0) |
+ (ev & EPOLLERR ? G_IO_ERR : 0);
+ }
+ }
+out:
+ return ret;
+}
+
+static bool aio_epoll_enabled(AioContext *ctx)
+{
+ /* Fall back to ppoll when external clients are disabled. */
+ return !aio_external_disabled(ctx) && ctx->epoll_enabled;
+}
+
+static bool aio_epoll_check_poll(AioContext *ctx, GPollFD *pfds,
+ unsigned npfd, int64_t timeout)
+{
+ if (!ctx->epoll_available) {
+ return false;
+ }
+ if (aio_epoll_enabled(ctx)) {
+ return true;
+ }
+ if (npfd >= EPOLL_ENABLE_THRESHOLD) {
+ if (aio_epoll_try_enable(ctx)) {
+ return true;
+ } else {
+ aio_epoll_disable(ctx);
+ }
+ }
+ return false;
+}
+
+#else
+
+static void aio_epoll_update(AioContext *ctx, AioHandler *node, bool is_new)
+{
+}
+
+static int aio_epoll(AioContext *ctx, GPollFD *pfds,
+ unsigned npfd, int64_t timeout)
+{
+ assert(false);
+}
+
+static bool aio_epoll_enabled(AioContext *ctx)
+{
+ return false;
+}
+
+static bool aio_epoll_check_poll(AioContext *ctx, GPollFD *pfds,
+ unsigned npfd, int64_t timeout)
+{
+ return false;
+}
+
+#endif
+
static AioHandler *find_aio_handler(AioContext *ctx, int fd)
{
AioHandler *node;
void aio_set_fd_handler(AioContext *ctx,
int fd,
+ bool is_external,
IOHandler *io_read,
IOHandler *io_write,
void *opaque)
{
AioHandler *node;
+ bool is_new = false;
+ bool deleted = false;
node = find_aio_handler(ctx, fd);
* releasing the walking_handlers lock.
*/
QLIST_REMOVE(node, node);
- g_free(node);
+ deleted = true;
}
}
} else {
if (node == NULL) {
/* Alloc and insert if it's not already there */
- node = g_malloc0(sizeof(AioHandler));
+ node = g_new0(AioHandler, 1);
node->pfd.fd = fd;
QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node);
g_source_add_poll(&ctx->source, &node->pfd);
+ is_new = true;
}
/* Update handler with latest information */
node->io_read = io_read;
node->io_write = io_write;
node->opaque = opaque;
- node->pollfds_idx = -1;
+ node->is_external = is_external;
node->pfd.events = (io_read ? G_IO_IN | G_IO_HUP | G_IO_ERR : 0);
node->pfd.events |= (io_write ? G_IO_OUT | G_IO_ERR : 0);
}
+ aio_epoll_update(ctx, node, is_new);
aio_notify(ctx);
+ if (deleted) {
+ g_free(node);
+ }
}
void aio_set_event_notifier(AioContext *ctx,
EventNotifier *notifier,
+ bool is_external,
EventNotifierHandler *io_read)
{
aio_set_fd_handler(ctx, event_notifier_get_fd(notifier),
- (IOHandler *)io_read, NULL, notifier);
+ is_external, (IOHandler *)io_read, NULL, notifier);
}
bool aio_prepare(AioContext *ctx)
int revents;
revents = node->pfd.revents & node->pfd.events;
- if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read) {
+ if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read &&
+ aio_node_check(ctx, node->is_external)) {
return true;
}
- if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write) {
+ if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write &&
+ aio_node_check(ctx, node->is_external)) {
return true;
}
}
if (!node->deleted &&
(revents & (G_IO_IN | G_IO_HUP | G_IO_ERR)) &&
+ aio_node_check(ctx, node->is_external) &&
node->io_read) {
node->io_read(node->opaque);
}
if (!node->deleted &&
(revents & (G_IO_OUT | G_IO_ERR)) &&
+ aio_node_check(ctx, node->is_external) &&
node->io_write) {
node->io_write(node->opaque);
progress = true;
return progress;
}
+/* These thread-local variables are used only in a small part of aio_poll
+ * around the call to the poll() system call. In particular they are not
+ * used while aio_poll is performing callbacks, which makes it much easier
+ * to think about reentrancy!
+ *
+ * Stack-allocated arrays would be perfect but they have size limitations;
+ * heap allocation is expensive enough that we want to reuse arrays across
+ * calls to aio_poll(). And because poll() has to be called without holding
+ * any lock, the arrays cannot be stored in AioContext. Thread-local data
+ * has none of the disadvantages of these three options.
+ */
+static __thread GPollFD *pollfds;
+static __thread AioHandler **nodes;
+static __thread unsigned npfd, nalloc;
+static __thread Notifier pollfds_cleanup_notifier;
+
+static void pollfds_cleanup(Notifier *n, void *unused)
+{
+ g_assert(npfd == 0);
+ g_free(pollfds);
+ g_free(nodes);
+ nalloc = 0;
+}
+
+static void add_pollfd(AioHandler *node)
+{
+ if (npfd == nalloc) {
+ if (nalloc == 0) {
+ pollfds_cleanup_notifier.notify = pollfds_cleanup;
+ qemu_thread_atexit_add(&pollfds_cleanup_notifier);
+ nalloc = 8;
+ } else {
+ g_assert(nalloc <= INT_MAX);
+ nalloc *= 2;
+ }
+ pollfds = g_renew(GPollFD, pollfds, nalloc);
+ nodes = g_renew(AioHandler *, nodes, nalloc);
+ }
+ nodes[npfd] = node;
+ pollfds[npfd] = (GPollFD) {
+ .fd = node->pfd.fd,
+ .events = node->pfd.events,
+ };
+ npfd++;
+}
+
bool aio_poll(AioContext *ctx, bool blocking)
{
AioHandler *node;
- bool was_dispatching;
- int ret;
+ int i, ret;
bool progress;
+ int64_t timeout;
- was_dispatching = ctx->dispatching;
+ aio_context_acquire(ctx);
progress = false;
/* aio_notify can avoid the expensive event_notifier_set if
* everything (file descriptors, bottom halves, timers) will
* be re-evaluated before the next blocking poll(). This is
* already true when aio_poll is called with blocking == false;
- * if blocking == true, it is only true after poll() returns.
- *
- * If we're in a nested event loop, ctx->dispatching might be true.
- * In that case we can restore it just before returning, but we
- * have to clear it now.
+ * if blocking == true, it is only true after poll() returns,
+ * so disable the optimization now.
*/
- aio_set_dispatching(ctx, !blocking);
+ if (blocking) {
+ atomic_add(&ctx->notify_me, 2);
+ }
ctx->walking_handlers++;
- g_array_set_size(ctx->pollfds, 0);
+ assert(npfd == 0);
/* fill pollfds */
QLIST_FOREACH(node, &ctx->aio_handlers, node) {
- node->pollfds_idx = -1;
- if (!node->deleted && node->pfd.events) {
- GPollFD pfd = {
- .fd = node->pfd.fd,
- .events = node->pfd.events,
- };
- node->pollfds_idx = ctx->pollfds->len;
- g_array_append_val(ctx->pollfds, pfd);
+ if (!node->deleted && node->pfd.events
+ && !aio_epoll_enabled(ctx)
+ && aio_node_check(ctx, node->is_external)) {
+ add_pollfd(node);
}
}
- ctx->walking_handlers--;
+ timeout = blocking ? aio_compute_timeout(ctx) : 0;
/* wait until next event */
- ret = qemu_poll_ns((GPollFD *)ctx->pollfds->data,
- ctx->pollfds->len,
- blocking ? aio_compute_timeout(ctx) : 0);
+ if (timeout) {
+ aio_context_release(ctx);
+ }
+ if (aio_epoll_check_poll(ctx, pollfds, npfd, timeout)) {
+ AioHandler epoll_handler;
+
+ epoll_handler.pfd.fd = ctx->epollfd;
+ epoll_handler.pfd.events = G_IO_IN | G_IO_OUT | G_IO_HUP | G_IO_ERR;
+ npfd = 0;
+ add_pollfd(&epoll_handler);
+ ret = aio_epoll(ctx, pollfds, npfd, timeout);
+ } else {
+ ret = qemu_poll_ns(pollfds, npfd, timeout);
+ }
+ if (blocking) {
+ atomic_sub(&ctx->notify_me, 2);
+ }
+ if (timeout) {
+ aio_context_acquire(ctx);
+ }
+
+ aio_notify_accept(ctx);
/* if we have any readable fds, dispatch event */
if (ret > 0) {
- QLIST_FOREACH(node, &ctx->aio_handlers, node) {
- if (node->pollfds_idx != -1) {
- GPollFD *pfd = &g_array_index(ctx->pollfds, GPollFD,
- node->pollfds_idx);
- node->pfd.revents = pfd->revents;
- }
+ for (i = 0; i < npfd; i++) {
+ nodes[i]->pfd.revents = pollfds[i].revents;
}
}
+ npfd = 0;
+ ctx->walking_handlers--;
+
/* Run dispatch even if there were no readable fds to run timers */
- aio_set_dispatching(ctx, true);
if (aio_dispatch(ctx)) {
progress = true;
}
- aio_set_dispatching(ctx, was_dispatching);
+ aio_context_release(ctx);
+
return progress;
}
+
+void aio_context_setup(AioContext *ctx)
+{
+#ifdef CONFIG_EPOLL_CREATE1
+ assert(!ctx->epollfd);
+ ctx->epollfd = epoll_create1(EPOLL_CLOEXEC);
+ if (ctx->epollfd == -1) {
+ fprintf(stderr, "Failed to create epoll instance: %s", strerror(errno));
+ ctx->epoll_available = false;
+ } else {
+ ctx->epoll_available = true;
+ }
+#endif
+}
projects / qemu.git / blobdiff