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2017-02-21monitor: add poll-* properties into query-iothreads resultPavel Hrdina1-0/+3
IOthreads were recently extended by new properties that can enable/disable and configure aio polling. This will also allow other tools that uses QEMU to probe for existence of those new properties via query-qmp-schema. Signed-off-by: Pavel Hrdina <phrdina@redhat.com> Message-Id: <3163c16d6ab4257f7be9ad44fe9cc0ce8c359e5a.1486718555.git.phrdina@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
2017-02-03iothread: enable AioContext polling by defaultStefan Hajnoczi1-0/+14
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: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20170126170119.27876-1-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-01-03iothread: add poll-grow and poll-shrink parametersStefan Hajnoczi1-11/+45
These parameters control the poll time self-tuning algorithm. They are optional and will default to sane values if omitted. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20161201192652.9509-14-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-01-03aio: self-tune polling timeStefan Hajnoczi1-2/+2
This patch is based on the algorithm for the kvm.ko halt_poll_ns parameter in Linux. The initial polling time is zero. If the event loop is woken up within the maximum polling time it means polling could be effective, so grow polling time. If the event loop is woken up beyond the maximum polling time it means polling is not effective, so shrink polling time. If the event loop makes progress within the current polling time then the sweet spot has been reached. This algorithm adjusts the polling time so it can adapt to variations in workloads. The goal is to reach the sweet spot while also recognizing when polling would hurt more than help. Two new trace events, poll_grow and poll_shrink, are added for observing polling time adjustment. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20161201192652.9509-13-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-01-03iothread: add polling parametersStefan Hajnoczi1-0/+50
Poll mode can be configured with -object iothread,poll-max-ns=NUM. Polling is disabled with a value of 0 nanoseconds. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20161201192652.9509-7-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-10-28iothread: release AioContext around aio_pollPaolo Bonzini1-9/+2
This is the first step towards having fine-grained critical sections in dataplane threads, which will resolve lock ordering problems between address_space_* functions (which need the BQL when doing MMIO, even after we complete RCU-based dispatch) and the AioContext. Because AioContext does not use contention callbacks anymore, the unit test has to be changed. Previously applied as a0710f7995f914e3044e5899bd8ff6c43c62f916 and then reverted. Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <1477565348-5458-19-git-send-email-pbonzini@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
2016-10-28iothread: detach all block devices before stopping themPaolo Bonzini1-0/+13
Soon bdrv_drain will not call aio_poll itself on iothreads. If block devices are left hanging off the iothread's AioContext, there will be no one to do I/O for those poor devices. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Message-Id: <1477565348-5458-13-git-send-email-pbonzini@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
2016-10-28aio: introduce qemu_get_current_aio_contextPaolo Bonzini1-0/+9
This will be used by BDRV_POLL_WHILE (and thus by bdrv_drain) to choose how to wait for I/O completion. Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <1477565348-5458-12-git-send-email-pbonzini@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
2016-09-28iothread: check iothread->ctx before aio_context_unref to avoid assertionLin Ma1-0/+3
if iothread->ctx is set to NULL, aio_context_unref triggers the assertion: g_source_unref: assertion 'source != NULL' failed. The patch fixes it. Signed-off-by: Lin Ma <lma@suse.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20160926052958.10716-1-lma@suse.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-09-13iothread: Stop threads before main() quitsFam Zheng1-4/+20
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: Fam Zheng <famz@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 1473326931-9699-1-git-send-email-famz@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-02-04all: Clean up includesPeter Maydell1-0/+1
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: Peter Maydell <peter.maydell@linaro.org> Message-id: 1454089805-5470-16-git-send-email-peter.maydell@linaro.org
2015-12-03iothread: include id in thread namePaolo Bonzini1-1/+6
This makes it easier to find the desired thread. Use "IO" plus the id; even with the 14 character limit on the thread name, enough of the id should be readable (e.g. "IO iothreadNNN" with three characters for the number). Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Message-id: 1448372804-5034-1-git-send-email-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2015-07-24rcu: actually register threads that have RCU read-side critical sectionsPaolo Bonzini1-0/+5
Otherwise, grace periods are detected too early! Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-06-19qom: Add helper function for getting user objects rootDaniel P. Berrange1-3/+1
Add object_get_objects_root() function which is a convenience for obtaining the Object * located at /objects in the object composition tree. Convert existing code over to use the new API where appropriate. Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Andreas Färber <afaerber@suse.de>
2015-06-12Revert "iothread: release iothread around aio_poll"Stefan Hajnoczi1-2/+9
This reverts commit a0710f7995f914e3044e5899bd8ff6c43c62f916. In qemu-devel email message <556DBF87.2020908@de.ibm.com>, Christian Borntraeger writes: Having many guests all with a kernel/ramdisk (via -kernel) and several null block devices will result in hangs. All hanging guests are in partition detection code waiting for an I/O to return so very early maybe even the first I/O. Reverting that commit "fixes" the hangs. Reverting this commit for the 2.4 release. More time is needed to investigate and correct this patch. Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2015-05-08Remove various unused functionsThomas Huth1-12/+0
The functions tpm_backend_thread_tpm_reset() and iothread_find() are completely unused, let's remove them. Signed-off-by: Thomas Huth <huth@tuxfamily.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2015-04-28iothread: release iothread around aio_pollPaolo Bonzini1-9/+2
This is the first step towards having fine-grained critical sections in dataplane threads, which resolves lock ordering problems between address_space_* functions (which need the BQL when doing MMIO, even after we complete RCU-based dispatch) and the AioContext. Because AioContext does not use contention callbacks anymore, the unit test has to be changed. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 1424449612-18215-4-git-send-email-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-09-22async: aio_context_new(): Handle event_notifier_init failureChrysostomos Nanakos1-1/+10
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: Chrysostomos Nanakos <cnanakos@grnet.gr> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-07-14AioContext: do not rely on aio_poll(ctx, true) result to end a loopPaolo Bonzini1-1/+4
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: Christian Borntraeger <borntraeger@de.ibm.com> Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-04-04iothread: make IOThread struct definition publicStefan Hajnoczi1-11/+0
Make the IOThread struct definition public so objects can be embedded in parent structs. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-03-13qmp: add query-iothreads commandStefan Hajnoczi1-0/+36
The "query-iothreads" command returns a list of information about iothreads. See the patch for API documentation. Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-03-13iothread: stash thread ID awayStefan Hajnoczi1-0/+22
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: Stefan Hajnoczi <stefanha@redhat.com>
2014-03-13iothread: add I/O thread objectStefan Hajnoczi1-0/+120
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: Stefan Hajnoczi <stefanha@redhat.com>
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