From: Stefan Hajnoczi <stefanha@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Fam Zheng" <fam@euphon.net>, "Kevin Wolf" <kwolf@redhat.com>,
qemu-block@nongnu.org, "Max Reitz" <mreitz@redhat.com>,
"Stefan Hajnoczi" <stefanha@redhat.com>,
"Marc-André Lureau" <marcandre.lureau@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>
Subject: [PATCH 4/5] aio-posix: make AioHandler deletion O(1)
Date: Fri, 14 Feb 2020 17:17:11 +0000 [thread overview]
Message-ID: <20200214171712.541358-5-stefanha@redhat.com> (raw)
In-Reply-To: <20200214171712.541358-1-stefanha@redhat.com>
It is not necessary to scan all AioHandlers for deletion. Keep a list
of deleted handlers instead of scanning the full list of all handlers.
The AioHandler->deleted field can be dropped. Let's check if the
handler has been inserted into the deleted list instead. Add a new
QLIST_IS_INSERTED() API for this check.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
include/block/aio.h | 6 ++++-
include/qemu/queue.h | 3 +++
util/aio-posix.c | 53 +++++++++++++++++++++++++++++---------------
3 files changed, 43 insertions(+), 19 deletions(-)
diff --git a/include/block/aio.h b/include/block/aio.h
index 7ba9bd7874..1a0de1508c 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -42,6 +42,7 @@ void qemu_aio_unref(void *p);
void qemu_aio_ref(void *p);
typedef struct AioHandler AioHandler;
+typedef QLIST_HEAD(, AioHandler) AioHandlerList;
typedef void QEMUBHFunc(void *opaque);
typedef bool AioPollFn(void *opaque);
typedef void IOHandler(void *opaque);
@@ -58,7 +59,10 @@ struct AioContext {
QemuRecMutex lock;
/* The list of registered AIO handlers. Protected by ctx->list_lock. */
- QLIST_HEAD(, AioHandler) aio_handlers;
+ AioHandlerList aio_handlers;
+
+ /* The list of AIO handlers to be deleted. Protected by ctx->list_lock. */
+ AioHandlerList deleted_aio_handlers;
/* Used to avoid unnecessary event_notifier_set calls in aio_notify;
* accessed with atomic primitives. If this field is 0, everything
diff --git a/include/qemu/queue.h b/include/qemu/queue.h
index a276363372..699a8a0568 100644
--- a/include/qemu/queue.h
+++ b/include/qemu/queue.h
@@ -158,6 +158,9 @@ struct { \
} \
} while (/*CONSTCOND*/0)
+/* Is elm in a list? */
+#define QLIST_IS_INSERTED(elm, field) ((elm)->field.le_prev != NULL)
+
#define QLIST_FOREACH(var, head, field) \
for ((var) = ((head)->lh_first); \
(var); \
diff --git a/util/aio-posix.c b/util/aio-posix.c
index b21bcd8e97..3a98a2acb9 100644
--- a/util/aio-posix.c
+++ b/util/aio-posix.c
@@ -31,10 +31,10 @@ struct AioHandler
AioPollFn *io_poll;
IOHandler *io_poll_begin;
IOHandler *io_poll_end;
- int deleted;
void *opaque;
bool is_external;
QLIST_ENTRY(AioHandler) node;
+ QLIST_ENTRY(AioHandler) node_deleted;
};
#ifdef CONFIG_EPOLL_CREATE1
@@ -67,7 +67,7 @@ static bool aio_epoll_try_enable(AioContext *ctx)
QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
int r;
- if (node->deleted || !node->pfd.events) {
+ if (QLIST_IS_INSERTED(node, node_deleted) || !node->pfd.events) {
continue;
}
event.events = epoll_events_from_pfd(node->pfd.events);
@@ -195,9 +195,11 @@ static AioHandler *find_aio_handler(AioContext *ctx, int fd)
AioHandler *node;
QLIST_FOREACH(node, &ctx->aio_handlers, node) {
- if (node->pfd.fd == fd)
- if (!node->deleted)
+ if (node->pfd.fd == fd) {
+ if (!QLIST_IS_INSERTED(node, node_deleted)) {
return node;
+ }
+ }
}
return NULL;
@@ -216,7 +218,7 @@ static bool aio_remove_fd_handler(AioContext *ctx, AioHandler *node)
/* If a read is in progress, just mark the node as deleted */
if (qemu_lockcnt_count(&ctx->list_lock)) {
- node->deleted = 1;
+ QLIST_INSERT_HEAD_RCU(&ctx->deleted_aio_handlers, node, node_deleted);
node->pfd.revents = 0;
return false;
}
@@ -358,7 +360,7 @@ static void poll_set_started(AioContext *ctx, bool started)
QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
IOHandler *fn;
- if (node->deleted) {
+ if (QLIST_IS_INSERTED(node, node_deleted)) {
continue;
}
@@ -415,6 +417,26 @@ bool aio_pending(AioContext *ctx)
return result;
}
+static void aio_free_deleted_handlers(AioContext *ctx)
+{
+ AioHandler *node;
+
+ if (QLIST_EMPTY_RCU(&ctx->deleted_aio_handlers)) {
+ return;
+ }
+ if (!qemu_lockcnt_dec_if_lock(&ctx->list_lock)) {
+ return; /* we are nested, let the parent do the freeing */
+ }
+
+ while ((node = QLIST_FIRST_RCU(&ctx->deleted_aio_handlers))) {
+ QLIST_REMOVE(node, node);
+ QLIST_REMOVE(node, node_deleted);
+ g_free(node);
+ }
+
+ qemu_lockcnt_inc_and_unlock(&ctx->list_lock);
+}
+
static bool aio_dispatch_handlers(AioContext *ctx)
{
AioHandler *node, *tmp;
@@ -426,7 +448,7 @@ static bool aio_dispatch_handlers(AioContext *ctx)
revents = node->pfd.revents & node->pfd.events;
node->pfd.revents = 0;
- if (!node->deleted &&
+ if (!QLIST_IS_INSERTED(node, node_deleted) &&
(revents & (G_IO_IN | G_IO_HUP | G_IO_ERR)) &&
aio_node_check(ctx, node->is_external) &&
node->io_read) {
@@ -437,21 +459,13 @@ static bool aio_dispatch_handlers(AioContext *ctx)
progress = true;
}
}
- if (!node->deleted &&
+ if (!QLIST_IS_INSERTED(node, 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;
}
-
- if (node->deleted) {
- if (qemu_lockcnt_dec_if_lock(&ctx->list_lock)) {
- QLIST_REMOVE(node, node);
- g_free(node);
- qemu_lockcnt_inc_and_unlock(&ctx->list_lock);
- }
- }
}
return progress;
@@ -462,6 +476,7 @@ void aio_dispatch(AioContext *ctx)
qemu_lockcnt_inc(&ctx->list_lock);
aio_bh_poll(ctx);
aio_dispatch_handlers(ctx);
+ aio_free_deleted_handlers(ctx);
qemu_lockcnt_dec(&ctx->list_lock);
timerlistgroup_run_timers(&ctx->tlg);
@@ -519,7 +534,7 @@ static bool run_poll_handlers_once(AioContext *ctx, int64_t *timeout)
AioHandler *node;
QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
- if (!node->deleted && node->io_poll &&
+ if (!QLIST_IS_INSERTED(node, node_deleted) && node->io_poll &&
aio_node_check(ctx, node->is_external) &&
node->io_poll(node->opaque)) {
/*
@@ -653,7 +668,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
if (!aio_epoll_enabled(ctx)) {
QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
- if (!node->deleted && node->pfd.events
+ if (!QLIST_IS_INSERTED(node, node_deleted) && node->pfd.events
&& aio_node_check(ctx, node->is_external)) {
add_pollfd(node);
}
@@ -730,6 +745,8 @@ bool aio_poll(AioContext *ctx, bool blocking)
progress |= aio_dispatch_handlers(ctx);
}
+ aio_free_deleted_handlers(ctx);
+
qemu_lockcnt_dec(&ctx->list_lock);
progress |= timerlistgroup_run_timers(&ctx->tlg);
--
2.24.1
next prev parent reply other threads:[~2020-02-14 17:19 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 17:17 [PATCH 0/5] aio-posix: towards an O(1) event loop Stefan Hajnoczi
2020-02-14 17:17 ` [PATCH 1/5] aio-posix: fix use after leaving scope in aio_poll() Stefan Hajnoczi
2020-02-19 7:02 ` Sergio Lopez
2020-02-14 17:17 ` [PATCH 2/5] aio-posix: don't pass ns timeout to epoll_wait() Stefan Hajnoczi
2020-02-19 10:12 ` Sergio Lopez
2020-02-14 17:17 ` [PATCH 3/5] qemu/queue.h: add QLIST_SAFE_REMOVE() Stefan Hajnoczi
2020-02-19 10:30 ` Sergio Lopez
2020-02-14 17:17 ` Stefan Hajnoczi [this message]
2020-02-19 10:41 ` [PATCH 4/5] aio-posix: make AioHandler deletion O(1) Sergio Lopez
2020-02-14 17:17 ` [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll Stefan Hajnoczi
2020-02-19 11:00 ` Sergio Lopez
2020-02-19 11:13 ` Paolo Bonzini
2020-02-21 12:59 ` Stefan Hajnoczi
2020-02-21 13:06 ` Paolo Bonzini
2020-02-21 14:44 ` Stefan Hajnoczi
2020-02-21 14:47 ` Stefan Hajnoczi
2020-02-21 15:04 ` Paolo Bonzini
2020-02-21 15:29 ` Stefan Hajnoczi
2020-02-21 15:37 ` Paolo Bonzini
2020-02-21 15:29 ` [PATCH 0/5] aio-posix: towards an O(1) event loop Stefan Hajnoczi
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