KVM Archive on lore.kernel.org
 help / color / Atom feed
From: "Longpeng (Mike)" <longpeng2@huawei.com>
To: Alex Williamson <alex.williamson@redhat.com>, <pbonzini@redhat.com>
Cc: <qemu-devel@nongnu.org>, <kvm@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>,
	"Longpeng(Mike)" <longpeng.mike@gmail.com>,
	Gonglei <arei.gonglei@huawei.com>,
	Huangzhichao <huangzhichao@huawei.com>
Subject: vfio_pin_map_dma cause synchronize_sched wait too long
Date: Mon, 2 Dec 2019 17:10:26 +0800
Message-ID: <2e53a9f0-3225-d416-98ff-55bd337330bc@huawei.com> (raw)

Hi guys,

Suppose there're two VMs: VM1 is bind to node-0 and calling vfio_pin_map_dma(),
VM2 is a migrate incoming VM which bind to node-1. We found the vm_start( QEMU
function) of VM2 will take too long occasionally, the reason is as follow.

- VM2 -
qemu: vm_start
        vm_start_notify
          virtio_vmstate_change
            virtio_pci_vmstate_change
              virtio_pci_start_ioeventfd
                virtio_device_start_ioeventfd_impl
                  event_notifier_init
                    eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC) <-- too long
kern: sys_eventfd2
        get_unused_fd_flags
          __alloc_fd
            expand_files
              expand_fdtable
                synchronize_sched <-- too long

- VM1 -
The VM1 is doing vfio_pin_map_dma at the same time.

The CPU must finish vfio_pin_map_dma and then rcu-sched grace period can be
elapsed, so synchronize_sched would wait for a long time.

Is there any solution to this ? Any suggestion would be greatly appreciated, thanks!

-- 
Regards,
Longpeng(Mike)


             reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-02  9:10 Longpeng (Mike) [this message]
2019-12-02  9:31 ` Paolo Bonzini
2019-12-02  9:42   ` Longpeng (Mike)
2019-12-02 10:06     ` Paolo Bonzini
2019-12-02 10:47       ` Longpeng (Mike)

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=2e53a9f0-3225-d416-98ff-55bd337330bc@huawei.com \
    --to=longpeng2@huawei.com \
    --cc=alex.williamson@redhat.com \
    --cc=arei.gonglei@huawei.com \
    --cc=huangzhichao@huawei.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=longpeng.mike@gmail.com \
    --cc=pbonzini@redhat.com \
    --cc=qemu-devel@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvm/0 kvm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvm kvm/ https://lore.kernel.org/kvm \
		kvm@vger.kernel.org
	public-inbox-index kvm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.kvm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git