Skip to content
Snippets Groups Projects
Select Git revision
  • feature/libtcg-rebase default protected
1 result
Search by author
  • Any Author
  • Anton Anton anjo
1 author
  1. Feb 03, 2017
    • Stefan Hajnoczi's avatar
      iothread: enable AioContext polling by default · cdd7abfd
      Stefan Hajnoczi authored 
      
IOThread AioContexts are likely to consist only of event sources like
virtqueue ioeventfds and LinuxAIO completion eventfds that are pollable
from userspace (without system calls).

We recently merged the AioContext polling feature but didn't enable it
by default yet.  I have gone back over the performance data on the
mailing list and picked a default polling value that gave good results.

Let's enable AioContext polling by default so users don't have another
switch they need to set manually.  If performance regressions are found
we can still disable this for the QEMU 2.9 release.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Karl Rister <krister@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170126170119.27876-1-stefanha@redhat.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
      cdd7abfd
  3. Jan 03, 2017
  5. Oct 28, 2016
  7. Sep 28, 2016
  9. Sep 13, 2016
    • Fam Zheng's avatar
      iothread: Stop threads before main() quits · dce8921b
      Fam Zheng authored 
      
Right after main_loop ends, we release various things but keep iothread
alive. The latter is not prepared to the sudden change of resources.

Specifically, after bdrv_close_all(), virtio-scsi dataplane get a
surprise at the empty BlockBackend:

(gdb) bt
    at /usr/src/debug/qemu-2.6.0/hw/scsi/virtio-scsi.c:543
    at /usr/src/debug/qemu-2.6.0/hw/scsi/virtio-scsi.c:577

It is because the d->conf.blk->root is set to NULL, then
blk_get_aio_context() returns qemu_aio_context, whereas s->ctx is still
pointing to the iothread:

    hw/scsi/virtio-scsi.c:543:

    if (s->dataplane_started) {
        assert(blk_get_aio_context(d->conf.blk) == s->ctx);
    }

To fix this, let's stop iothreads before doing bdrv_close_all().

Cc: qemu-stable@nongnu.org
Signed-off-by: default avatarFam Zheng <famz@redhat.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-id: 1473326931-9699-1-git-send-email-famz@redhat.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
      dce8921b
  11. Feb 04, 2016
    • Peter Maydell's avatar
      all: Clean up includes · d38ea87a
      Peter Maydell authored 
      
Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.

This commit was created with scripts/clean-includes.

Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Message-id: 1454089805-5470-16-git-send-email-peter.maydell@linaro.org
      d38ea87a
  13. Dec 03, 2015
  15. Jul 24, 2015
  17. Jun 19, 2015
  19. Jun 12, 2015
  21. May 08, 2015
  23. Apr 28, 2015
  25. Sep 22, 2014
    • Chrysostomos Nanakos's avatar
      async: aio_context_new(): Handle event_notifier_init failure · 2f78e491
      Chrysostomos Nanakos authored 
      
On a system with a low limit of open files the initialization
of the event notifier could fail and QEMU exits without printing any
error information to the user.

The problem can be easily reproduced by enforcing a low limit of open
files and start QEMU with enough I/O threads to hit this limit.

The same problem raises, without the creation of I/O threads, while
QEMU initializes the main event loop by enforcing an even lower limit of
open files.

This commit adds an error message on failure:

 # qemu [...] -object iothread,id=iothread0 -object iothread,id=iothread1
 qemu: Failed to initialize event notifier: Too many open files in system

Signed-off-by: default avatarChrysostomos Nanakos <cnanakos@grnet.gr>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
      2f78e491
  27. Jul 14, 2014
    • Paolo Bonzini's avatar
      AioContext: do not rely on aio_poll(ctx, true) result to end a loop · acfb23ad
      Paolo Bonzini authored 
      
Currently, whenever aio_poll(ctx, true) has completed all pending
work it returns true *and* the next call to aio_poll(ctx, true)
will not block.

This invariant has its roots in qemu_aio_flush()'s implementation
as "while (qemu_aio_wait()) {}".  However, qemu_aio_flush() does
not exist anymore and bdrv_drain_all() is implemented differently;
and this invariant is complicated to maintain and subtly different
from the return value of GMainLoop's g_main_context_iteration.

All calls to aio_poll(ctx, true) except one are guarded by a
while() loop checking for a request to be incomplete, or a
BlockDriverState to be idle.  The one remaining call (in
iothread.c) uses this to delay the aio_context_release/acquire
pair until the AioContext is quiescent, however:

- we can do the same just by using non-blocking aio_poll,
  similar to how vl.c invokes main_loop_wait

- it is buggy, because it does not ensure that the AioContext
  is released between an aio_notify and the next time the
  iothread goes to sleep.  This leads to hangs when stopping
  the dataplane thread.

In the end, these semantics are a bad match for the current
users of AioContext.  So modify that one exception in iothread.c,
which also fixes the hangs, as well as the testcase so that
it use the same idiom as the actual QEMU code.

Reported-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Tested-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
      acfb23ad
  29. Apr 04, 2014
  31. Mar 13, 2014
    • Stefan Hajnoczi's avatar
      qmp: add query-iothreads command · dc3dd0d2
      Stefan Hajnoczi authored 
      
The "query-iothreads" command returns a list of information about
iothreads.  See the patch for API documentation.

Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
      dc3dd0d2
    • Stefan Hajnoczi's avatar
      iothread: stash thread ID away · 88eb7c29
      Stefan Hajnoczi authored 
      
Keep the thread ID around so we can report it via QMP.

There's only one problem: qemu_get_thread_id() (gettid() wrapper on
Linux) must be called from the thread itself.  There is no way to get
the thread ID outside the thread.

This patch uses a condvar to wait for iothread_run() to populate the
thread_id inside the thread.

Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
      88eb7c29
    • Stefan Hajnoczi's avatar
      iothread: add I/O thread object · be8d8537
      Stefan Hajnoczi authored 
      
This is a stand-in for Michael Roth's QContext.  I expect this to be
replaced once QContext is completed.

The IOThread object is an AioContext event loop thread.  This patch adds
the concept of multiple event loop threads, allowing users to define
them.

When SMP guests run on SMP hosts it makes sense to instantiate multiple
IOThreads.  This spreads event loop processing across multiple cores.
Note that additional patches are required to actually bind a device to
an IOThread.

[Andreas Färber <afaerber@suse.de> pointed out that the embedded parent
object instance should be called "parent_obj" and have a newline
afterwards.  This patch has been changed to reflect this.
-- Stefan]

Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
      be8d8537