aio-posix: disable fdmon-io_uring when GSource is used

The glib event loop does not call fdmon_io_uring_wait() so fd handlers
waiting to be submitted build up in the list. There is no benefit is
using io_uring when the glib GSource is being used, so disable it
instead of implementing a more complex fix.

This fixes a memory leak where AioHandlers would build up and increasing
amounts of CPU time were spent iterating them in aio_pending(). The
symptom is that guests become slow when QEMU is built with io_uring
support.

Buglink: https://bugs.launchpad.net/qemu/+bug/1877716
Fixes: 73fd282e7b ("aio-posix: add io_uring fd monitoring implementation")
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Oleksandr Natalenko <oleksandr@redhat.com>
Message-id: 20200511183630.279750-3-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2020-05-11 19:36:30 +01:00
parent de137e44f7
commit ba607ca8bf
4 changed files with 20 additions and 0 deletions

View file

@ -701,6 +701,9 @@ void aio_context_setup(AioContext *ctx);
*/
void aio_context_destroy(AioContext *ctx);
/* Used internally, do not call outside AioContext code */
void aio_context_use_g_source(AioContext *ctx);
/**
* aio_context_set_poll_params:
* @ctx: the aio context

View file

@ -682,6 +682,18 @@ void aio_context_destroy(AioContext *ctx)
aio_free_deleted_handlers(ctx);
}
void aio_context_use_g_source(AioContext *ctx)
{
/*
* Disable io_uring when the glib main loop is used because it doesn't
* support mixed glib/aio_poll() usage. It relies on aio_poll() being
* called regularly so that changes to the monitored file descriptors are
* submitted, otherwise a list of pending fd handlers builds up.
*/
fdmon_io_uring_destroy(ctx);
aio_free_deleted_handlers(ctx);
}
void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
int64_t grow, int64_t shrink, Error **errp)
{

View file

@ -414,6 +414,10 @@ void aio_context_destroy(AioContext *ctx)
{
}
void aio_context_use_g_source(AioContext *ctx)
{
}
void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
int64_t grow, int64_t shrink, Error **errp)
{

View file

@ -362,6 +362,7 @@ static GSourceFuncs aio_source_funcs = {
GSource *aio_get_g_source(AioContext *ctx)
{
aio_context_use_g_source(ctx);
g_source_ref(&ctx->source);
return &ctx->source;
}