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authorStefan Hajnoczi <stefanha@redhat.com>2016-12-01 19:26:40 +0000
committerStefan Hajnoczi <stefanha@redhat.com>2017-01-03 16:38:47 +0000
commit721671ade77f4046b45893fbb7864ca84b9504cd (patch)
tree46a5e927a01342c5818e6ba99f137a6ad6fbb9f8
parent0891ee111217101bce683e30ed9f08cf0cfcffd7 (diff)
downloadqemu-arm-721671ade77f4046b45893fbb7864ca84b9504cd.tar.gz
aio: add flag to skip fds to aio_dispatch()
Polling mode will not call ppoll(2)/epoll_wait(2). Therefore we know there are no fds ready and should avoid looping over fd handlers in aio_dispatch(). Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20161201192652.9509-2-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
-rw-r--r--aio-posix.c14
-rw-r--r--aio-win32.c6
-rw-r--r--async.c2
-rw-r--r--include/block/aio.h6
4 files changed, 20 insertions, 8 deletions
diff --git a/aio-posix.c b/aio-posix.c
index e13b9ab2b0..4ac2346370 100644
--- a/aio-posix.c
+++ b/aio-posix.c
@@ -290,9 +290,13 @@ 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;
/*
@@ -308,7 +312,9 @@ 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;
@@ -473,7 +479,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
ctx->walking_handlers--;
/* Run dispatch even if there were no readable fds to run timers */
- if (aio_dispatch(ctx)) {
+ if (aio_dispatch(ctx, ret > 0)) {
progress = true;
}
diff --git a/aio-win32.c b/aio-win32.c
index c8c249e260..3ef8ea4caa 100644
--- a/aio-win32.c
+++ b/aio-win32.c
@@ -271,12 +271,14 @@ static bool aio_dispatch_handlers(AioContext *ctx, HANDLE event)
return progress;
}
-bool aio_dispatch(AioContext *ctx)
+bool aio_dispatch(AioContext *ctx, bool dispatch_fds)
{
bool progress;
progress = aio_bh_poll(ctx);
- progress |= aio_dispatch_handlers(ctx, INVALID_HANDLE_VALUE);
+ if (dispatch_fds) {
+ progress |= aio_dispatch_handlers(ctx, INVALID_HANDLE_VALUE);
+ }
progress |= timerlistgroup_run_timers(&ctx->tlg);
return progress;
}
diff --git a/async.c b/async.c
index b2de360c23..52bdb8fb39 100644
--- a/async.c
+++ b/async.c
@@ -251,7 +251,7 @@ aio_ctx_dispatch(GSource *source,
AioContext *ctx = (AioContext *) source;
assert(callback == NULL);
- aio_dispatch(ctx);
+ aio_dispatch(ctx, true);
return true;
}
diff --git a/include/block/aio.h b/include/block/aio.h
index ca551e346f..c1519ec83a 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -295,8 +295,12 @@ bool aio_pending(AioContext *ctx);
/* Dispatch any pending callbacks from the GSource attached to the AioContext.
*
* This is used internally in the implementation of the GSource.
+ *
+ * @dispatch_fds: true to process fds, false to skip them
+ * (can be used as an optimization by callers that know there
+ * are no fds ready)
*/
-bool aio_dispatch(AioContext *ctx);
+bool aio_dispatch(AioContext *ctx, bool dispatch_fds);
/* Progress in completing AIO work to occur. This can issue new pending
* aio as a result of executing I/O completion or bh callbacks.