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aio-posix: make AioHandler deletion O(1)

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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>
Reviewed-by: Sergio Lopez <slp@redhat.com>
Message-id: 20200214171712.541358-5-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2020-02-14 17:17:11 +00:00
parent 195ed8cb36
commit 4749079ce0
3 changed files with 43 additions and 19 deletions
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6
include/block/aio.h
View File

@ -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);
@ -71,7 +72,10 @@ 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

3
include/qemu/queue.h
View File

@ -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); \

53
util/aio-posix.c
View File

@ -32,10 +32,10 @@ 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
@ -68,7 +68,7 @@ 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);
@ -196,9 +196,11 @@ 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;
@ -217,7 +219,7 @@ 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;
}
@ -359,7 +361,7 @@ 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;
}
@ -416,6 +418,26 @@ 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;
@ -427,7 +449,7 @@ 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) {
@ -438,21 +460,13 @@ 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;
@ -463,6 +477,7 @@ 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);
@ -530,7 +545,7 @@ static bool run_poll_handlers_once(AioContext *ctx, int64_t *timeout)
RCU_READ_LOCK_GUARD();
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)) {
/*
@ -664,7 +679,7 @@ 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);
}
@ -741,6 +756,8 @@ 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);