X-Git-Url: https://repo.jachan.dev/qemu.git/blobdiff_plain/49110174f8835ec3d5ca7fc076ee1f51c18564fe..b3ac5a0de9b88454e42d0ee2755cc1083ccc25bb:/aio-posix.c

diff --git a/aio-posix.c b/aio-posix.c
index 4abec38866..15855715d4 100644
--- a/aio-posix.c
+++ b/aio-posix.c
@@ -13,21 +13,180 @@
  * 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"
+#include "qemu/cutils.h"
+#include "trace.h"
+#ifdef CONFIG_EPOLL_CREATE1
+#include <sys/epoll.h>
+#endif
 
 struct AioHandler
 {
     GPollFD pfd;
     IOHandler *io_read;
     IOHandler *io_write;
+    AioPollFn *io_poll;
+    IOHandler *io_poll_begin;
+    IOHandler *io_poll_end;
     int deleted;
     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;
+    int ctl;
+
+    if (!ctx->epoll_enabled) {
+        return;
+    }
+    if (!node->pfd.events) {
+        ctl = EPOLL_CTL_DEL;
+    } else {
+        event.data.ptr = node;
+        event.events = epoll_events_from_pfd(node->pfd.events);
+        ctl = is_new ? EPOLL_CTL_ADD : EPOLL_CTL_MOD;
+    }
+
+    r = epoll_ctl(ctx->epollfd, ctl, 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;
@@ -43,31 +202,41 @@ static AioHandler *find_aio_handler(AioContext *ctx, int fd)
 
 void aio_set_fd_handler(AioContext *ctx,
                         int fd,
+                        bool is_external,
                         IOHandler *io_read,
                         IOHandler *io_write,
+                        AioPollFn *io_poll,
                         void *opaque)
 {
     AioHandler *node;
+    bool is_new = false;
+    bool deleted = false;
 
     node = find_aio_handler(ctx, fd);
 
     /* Are we deleting the fd handler? */
-    if (!io_read && !io_write) {
-        if (node) {
-            g_source_remove_poll(&ctx->source, &node->pfd);
-
-            /* If the lock is held, just mark the node as deleted */
-            if (ctx->walking_handlers) {
-                node->deleted = 1;
-                node->pfd.revents = 0;
-            } else {
-                /* Otherwise, delete it for real.  We can't just mark it as
-                 * deleted because deleted nodes are only cleaned up after
-                 * releasing the walking_handlers lock.
-                 */
-                QLIST_REMOVE(node, node);
-                g_free(node);
-            }
+    if (!io_read && !io_write && !io_poll) {
+        if (node == NULL) {
+            return;
+        }
+
+        g_source_remove_poll(&ctx->source, &node->pfd);
+
+        /* If the lock is held, just mark the node as deleted */
+        if (ctx->walking_handlers) {
+            node->deleted = 1;
+            node->pfd.revents = 0;
+        } else {
+            /* Otherwise, delete it for real.  We can't just mark it as
+             * deleted because deleted nodes are only cleaned up after
+             * releasing the walking_handlers lock.
+             */
+            QLIST_REMOVE(node, node);
+            deleted = true;
+        }
+
+        if (!node->io_poll) {
+            ctx->poll_disable_cnt--;
         }
     } else {
         if (node == NULL) {
@@ -77,29 +246,103 @@ void aio_set_fd_handler(AioContext *ctx,
             QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node);
 
             g_source_add_poll(&ctx->source, &node->pfd);
+            is_new = true;
+
+            ctx->poll_disable_cnt += !io_poll;
+        } else {
+            ctx->poll_disable_cnt += !io_poll - !node->io_poll;
         }
+
         /* Update handler with latest information */
         node->io_read = io_read;
         node->io_write = io_write;
+        node->io_poll = io_poll;
         node->opaque = opaque;
+        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_fd_poll(AioContext *ctx, int fd,
+                     IOHandler *io_poll_begin,
+                     IOHandler *io_poll_end)
+{
+    AioHandler *node = find_aio_handler(ctx, fd);
+
+    if (!node) {
+        return;
+    }
+
+    node->io_poll_begin = io_poll_begin;
+    node->io_poll_end = io_poll_end;
 }
 
 void aio_set_event_notifier(AioContext *ctx,
                             EventNotifier *notifier,
-                            EventNotifierHandler *io_read)
+                            bool is_external,
+                            EventNotifierHandler *io_read,
+                            AioPollFn *io_poll)
+{
+    aio_set_fd_handler(ctx, event_notifier_get_fd(notifier), is_external,
+                       (IOHandler *)io_read, NULL, io_poll, notifier);
+}
+
+void aio_set_event_notifier_poll(AioContext *ctx,
+                                 EventNotifier *notifier,
+                                 EventNotifierHandler *io_poll_begin,
+                                 EventNotifierHandler *io_poll_end)
 {
-    aio_set_fd_handler(ctx, event_notifier_get_fd(notifier),
-                       (IOHandler *)io_read, NULL, notifier);
+    aio_set_fd_poll(ctx, event_notifier_get_fd(notifier),
+                    (IOHandler *)io_poll_begin,
+                    (IOHandler *)io_poll_end);
+}
+
+static void poll_set_started(AioContext *ctx, bool started)
+{
+    AioHandler *node;
+
+    if (started == ctx->poll_started) {
+        return;
+    }
+
+    ctx->poll_started = started;
+
+    ctx->walking_handlers++;
+    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+        IOHandler *fn;
+
+        if (node->deleted) {
+            continue;
+        }
+
+        if (started) {
+            fn = node->io_poll_begin;
+        } else {
+            fn = node->io_poll_end;
+        }
+
+        if (fn) {
+            fn(node->opaque);
+        }
+    }
+    ctx->walking_handlers--;
 }
 
+
 bool aio_prepare(AioContext *ctx)
 {
+    /* Poll mode cannot be used with glib's event loop, disable it. */
+    poll_set_started(ctx, false);
+
     return false;
 }
 
@@ -111,10 +354,12 @@ bool aio_pending(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;
         }
     }
@@ -122,9 +367,13 @@ bool aio_pending(AioContext *ctx)
     return false;
 }
 
-bool aio_dispatch(AioContext *ctx)
+/*
+ * Note that dispatch_fds == false has the side-effect of post-poning the
+ * freeing of deleted handlers.
+ */
+bool aio_dispatch(AioContext *ctx, bool dispatch_fds)
 {
-    AioHandler *node;
+    AioHandler *node = NULL;
     bool progress = false;
 
     /*
@@ -140,7 +389,9 @@ bool aio_dispatch(AioContext *ctx)
      * We have to walk very carefully in case aio_set_fd_handler is
      * called while we're walking.
      */
-    node = QLIST_FIRST(&ctx->aio_handlers);
+    if (dispatch_fds) {
+        node = QLIST_FIRST(&ctx->aio_handlers);
+    }
     while (node) {
         AioHandler *tmp;
         int revents;
@@ -152,6 +403,7 @@ bool aio_dispatch(AioContext *ctx)
 
         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);
 
@@ -162,6 +414,7 @@ bool aio_dispatch(AioContext *ctx)
         }
         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;
@@ -230,52 +483,206 @@ static void add_pollfd(AioHandler *node)
     npfd++;
 }
 
+static bool run_poll_handlers_once(AioContext *ctx)
+{
+    bool progress = false;
+    AioHandler *node;
+
+    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+        if (!node->deleted && node->io_poll &&
+                node->io_poll(node->opaque)) {
+            progress = true;
+        }
+
+        /* Caller handles freeing deleted nodes.  Don't do it here. */
+    }
+
+    return progress;
+}
+
+/* run_poll_handlers:
+ * @ctx: the AioContext
+ * @max_ns: maximum time to poll for, in nanoseconds
+ *
+ * Polls for a given time.
+ *
+ * Note that ctx->notify_me must be non-zero so this function can detect
+ * aio_notify().
+ *
+ * Note that the caller must have incremented ctx->walking_handlers.
+ *
+ * Returns: true if progress was made, false otherwise
+ */
+static bool run_poll_handlers(AioContext *ctx, int64_t max_ns)
+{
+    bool progress;
+    int64_t end_time;
+
+    assert(ctx->notify_me);
+    assert(ctx->walking_handlers > 0);
+    assert(ctx->poll_disable_cnt == 0);
+
+    trace_run_poll_handlers_begin(ctx, max_ns);
+
+    end_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + max_ns;
+
+    do {
+        progress = run_poll_handlers_once(ctx);
+    } while (!progress && qemu_clock_get_ns(QEMU_CLOCK_REALTIME) < end_time);
+
+    trace_run_poll_handlers_end(ctx, progress);
+
+    return progress;
+}
+
+/* try_poll_mode:
+ * @ctx: the AioContext
+ * @blocking: busy polling is only attempted when blocking is true
+ *
+ * ctx->notify_me must be non-zero so this function can detect aio_notify().
+ *
+ * Note that the caller must have incremented ctx->walking_handlers.
+ *
+ * Returns: true if progress was made, false otherwise
+ */
+static bool try_poll_mode(AioContext *ctx, bool blocking)
+{
+    if (blocking && ctx->poll_max_ns && ctx->poll_disable_cnt == 0) {
+        /* See qemu_soonest_timeout() uint64_t hack */
+        int64_t max_ns = MIN((uint64_t)aio_compute_timeout(ctx),
+                             (uint64_t)ctx->poll_ns);
+
+        if (max_ns) {
+            poll_set_started(ctx, true);
+
+            if (run_poll_handlers(ctx, max_ns)) {
+                return true;
+            }
+        }
+    }
+
+    poll_set_started(ctx, false);
+
+    /* Even if we don't run busy polling, try polling once in case it can make
+     * progress and the caller will be able to avoid ppoll(2)/epoll_wait(2).
+     */
+    return run_poll_handlers_once(ctx);
+}
+
 bool aio_poll(AioContext *ctx, bool blocking)
 {
     AioHandler *node;
-    bool was_dispatching;
-    int i, ret;
+    int i;
+    int ret = 0;
     bool progress;
     int64_t timeout;
+    int64_t start = 0;
 
     aio_context_acquire(ctx);
-    was_dispatching = ctx->dispatching;
     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++;
 
-    assert(npfd == 0);
+    if (ctx->poll_max_ns) {
+        start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+    }
 
-    /* fill pollfds */
-    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
-        if (!node->deleted && node->pfd.events) {
-            add_pollfd(node);
+    if (try_poll_mode(ctx, blocking)) {
+        progress = true;
+    } else {
+        assert(npfd == 0);
+
+        /* fill pollfds */
+
+        if (!aio_epoll_enabled(ctx)) {
+            QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+                if (!node->deleted && node->pfd.events
+                    && aio_node_check(ctx, node->is_external)) {
+                    add_pollfd(node);
+                }
+            }
         }
-    }
 
-    timeout = blocking ? aio_compute_timeout(ctx) : 0;
+        timeout = blocking ? aio_compute_timeout(ctx) : 0;
+
+        /* wait until next event */
+        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 (timeout) {
+            aio_context_acquire(ctx);
+        }
+    }
 
-    /* wait until next event */
-    if (timeout) {
-        aio_context_release(ctx);
+    if (blocking) {
+        atomic_sub(&ctx->notify_me, 2);
     }
-    ret = qemu_poll_ns((GPollFD *)pollfds, npfd, timeout);
-    if (timeout) {
-        aio_context_acquire(ctx);
+
+    /* Adjust polling time */
+    if (ctx->poll_max_ns) {
+        int64_t block_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - start;
+
+        if (block_ns <= ctx->poll_ns) {
+            /* This is the sweet spot, no adjustment needed */
+        } else if (block_ns > ctx->poll_max_ns) {
+            /* We'd have to poll for too long, poll less */
+            int64_t old = ctx->poll_ns;
+
+            if (ctx->poll_shrink) {
+                ctx->poll_ns /= ctx->poll_shrink;
+            } else {
+                ctx->poll_ns = 0;
+            }
+
+            trace_poll_shrink(ctx, old, ctx->poll_ns);
+        } else if (ctx->poll_ns < ctx->poll_max_ns &&
+                   block_ns < ctx->poll_max_ns) {
+            /* There is room to grow, poll longer */
+            int64_t old = ctx->poll_ns;
+            int64_t grow = ctx->poll_grow;
+
+            if (grow == 0) {
+                grow = 2;
+            }
+
+            if (ctx->poll_ns) {
+                ctx->poll_ns *= grow;
+            } else {
+                ctx->poll_ns = 4000; /* start polling at 4 microseconds */
+            }
+
+            if (ctx->poll_ns > ctx->poll_max_ns) {
+                ctx->poll_ns = ctx->poll_max_ns;
+            }
+
+            trace_poll_grow(ctx, old, ctx->poll_ns);
+        }
     }
 
+    aio_notify_accept(ctx);
+
     /* if we have any readable fds, dispatch event */
     if (ret > 0) {
         for (i = 0; i < npfd; i++) {
@@ -287,13 +694,46 @@ bool aio_poll(AioContext *ctx, bool blocking)
     ctx->walking_handlers--;
 
     /* Run dispatch even if there were no readable fds to run timers */
-    aio_set_dispatching(ctx, true);
-    if (aio_dispatch(ctx)) {
+    if (aio_dispatch(ctx, ret > 0)) {
         progress = true;
     }
 
-    aio_set_dispatching(ctx, was_dispatching);
     aio_context_release(ctx);
 
     return progress;
 }
+
+void aio_context_setup(AioContext *ctx)
+{
+    /* TODO remove this in final patch submission */
+    if (getenv("QEMU_AIO_POLL_MAX_NS")) {
+        fprintf(stderr, "The QEMU_AIO_POLL_MAX_NS environment variable has "
+                "been replaced with -object iothread,poll-max-ns=NUM\n");
+        exit(1);
+    }
+
+#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
+}
+
+void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
+                                 int64_t grow, int64_t shrink, Error **errp)
+{
+    /* No thread synchronization here, it doesn't matter if an incorrect value
+     * is used once.
+     */
+    ctx->poll_max_ns = max_ns;
+    ctx->poll_ns = 0;
+    ctx->poll_grow = grow;
+    ctx->poll_shrink = shrink;
+
+    aio_notify(ctx);
+}