Commit ba607ca8 authored by Stefan Hajnoczi's avatar Stefan Hajnoczi
Browse files

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: 73fd282e ("aio-posix: add io_uring fd monitoring implementation")
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Tested-by: default avatarOleksandr Natalenko <oleksandr@redhat.com>
Message-id: 20200511183630.279750-3-stefanha@redhat.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent de137e44

include/block/aio.h

+3 −0
Original line number Diff line number Diff line
@@ -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

util/aio-posix.c

+12 −0
Original line number Diff line number Diff line
@@ -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)

{

util/aio-win32.c

+4 −0
Original line number Diff line number Diff line
@@ -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)

{

util/async.c

+1 −0
Original line number Diff line number Diff line
@@ -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;

}