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Re: [Qemu-devel] [PATCH 17/23] hyperv: add synic message delivery
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 17/23] hyperv: add synic message delivery |
Date: |
Wed, 14 Jun 2017 17:32:12 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 |
On 14/06/2017 17:28, Roman Kagan wrote:
> On Wed, Jun 14, 2017 at 05:08:02PM +0200, Paolo Bonzini wrote:
>>
>>
>> On 06/06/2017 20:19, Roman Kagan wrote:
>>> + sint_route->msg_status = ret;
>>> + /* notify the msg originator of the progress made; if the slot was
>>> busy we
>>> + * set msg_pending flag in it so it will be the guest who will do EOM
>>> and
>>> + * trigger the notification from KVM via sint_ack_notifier */
>>> + if (ret != -EAGAIN) {
>>> + qemu_bh_schedule(sint_route->msg_bh);
>>> + }
>>
>> It may be faster to use aio_bh_schedule_oneshot, depending on the number
>> of devices.
>
> Messages aren't used on fast paths, they are only exchanged at device
> setup/teardown. So I cared more about readability than speed here.
Then you really want to use aio_bh_schedule_oneshot, because bottom
halves incur a (small) cost even when you don't use them: each iteration
of the event loop visits the list of bottom halves.
Persistent bottom halves, thus, are only a good idea if they are
expected to trigger very often on a busy VM. If this bottom half is
only triggered at setup/teardown, it shouldn't use them.
Paolo
- Re: [Qemu-devel] [PATCH 13/23] hyperv: qdev-ify SynIC, (continued)
[Qemu-devel] [PATCH 15/23] hyperv: make overlay pages for SynIC, Roman Kagan, 2017/06/06
[Qemu-devel] [PATCH 19/23] hyperv: process SIGNAL_EVENT hypercall, Roman Kagan, 2017/06/06
[Qemu-devel] [PATCH 18/23] hyperv: add synic event flag signaling, Roman Kagan, 2017/06/06
[Qemu-devel] [PATCH 17/23] hyperv: add synic message delivery, Roman Kagan, 2017/06/06
[Qemu-devel] [PATCH 22/23] MAINTAINERS: add myself and eyakovlev@ for hyperv*, Roman Kagan, 2017/06/06
[Qemu-devel] [PATCH 20/23] hyperv: process POST_MESSAGE hypercall, Roman Kagan, 2017/06/06
[Qemu-devel] [PATCH 21/23] hyperv_testdev: add SynIC message and event testmodes, Roman Kagan, 2017/06/06
[Qemu-devel] [PATCH 16/23] hyperv: map overlay pages after updating msrs, Roman Kagan, 2017/06/06