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Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion
From: |
Rik van Riel |
Subject: |
Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion |
Date: |
Tue, 25 Jul 2017 16:59:35 -0400 |
On Tue, 2017-07-25 at 07:46 -0700, Dan Williams wrote:
> On Tue, Jul 25, 2017 at 7:27 AM, Pankaj Gupta <address@hidden>
> wrote:
> >
> > Looks like only way to send flush(blk dev) from guest to host with
> > nvdimm
> > is using flush hint addresses. Is this the correct interface I am
> > looking?
> >
> > blkdev_issue_flush
> > submit_bio_wait
> > submit_bio
> > generic_make_request
> > pmem_make_request
> > ...
> > if (bio->bi_opf & REQ_FLUSH)
> > nvdimm_flush(nd_region);
>
> I would inject a paravirtualized version of pmem_make_request() that
> sends an async flush operation over virtio to the host. Don't try to
> use flush hint addresses for this, they don't have the proper
> semantics. The guest should be allowed to issue the flush and receive
> the completion asynchronously rather than taking a vm exist and
> blocking on that request.
That is my feeling, too. A slower IO device benefits
greatly from an asynchronous flush mechanism.
--
All rights reversed
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- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, (continued)
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Rik van Riel, 2017/07/23
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Dan Williams, 2017/07/23
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Jan Kara, 2017/07/24
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Pankaj Gupta, 2017/07/24
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Jan Kara, 2017/07/24
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Dan Williams, 2017/07/24
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Jan Kara, 2017/07/24
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Dan Williams, 2017/07/24
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Pankaj Gupta, 2017/07/25
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Dan Williams, 2017/07/25
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion,
Rik van Riel <=
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Pankaj Gupta, 2017/07/26
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Rik van Riel, 2017/07/26
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Dan Williams, 2017/07/26
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Rik van Riel, 2017/07/26
- Re: [Qemu-devel] KVM "fake DAX" flushing interface - discussion, Dan Williams, 2017/07/26