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Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates |
Date: |
Thu, 30 Nov 2017 12:08:06 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
* Igor Mammedov (address@hidden) wrote:
> On Wed, 29 Nov 2017 18:50:19 +0000
> "Dr. David Alan Gilbert (git)" <address@hidden> wrote:
>
> > From: "Dr. David Alan Gilbert" <address@hidden>
> >
> > Hi,
> > This is an experimental set that reworks the way the vhost
> > code handles changes in physical address space layout that
> > came from a discussion with Igor.
> Thanks for looking into it.
>
>
> > Instead of updating and trying to merge sections of address
> > space on each add/remove callback, we wait until the commit phase
> > and go through and rebuild a list by walking the Flatview of
> > memory and end up producing an ordered list.
> > We compare the list to the old list to trigger updates.
> >
> > Note, only very lightly tested so far, I'm just trying to see if it's
> > the right shape.
> >
> > Igor, is this what you were intending?
>
> I was thinking about a little less intrusive approach
>
> where vhost_region_add/del are modified to maintain
> sorted by GPA array of mem_sections, vhost_dev::mem is dropped
> altogether and vhost_memory_region array is build/used/freed
> on every vhost_commit().
> Maintaining sorted array should roughly cost us O(2 log n) if
> binary search is used.
>
> However I like your idea with iterator even more as it have
> potential to make it even faster O(n) if we get rid of
> quadratic and relatively complex vhost_update_compare_list().
Note vhost_update_compare_list is complex, but it is O(n) - it's
got nested loops, but the inner loop moves forward and oldi never
gets reset back to zero.
> Pls, see comments on individual patches.
Thanks; I have fixed a couple of bugs since I posted, so I'm
more interested in structure/shape. Any good ideas how to test
it are welcome.
Dave
>
> > Dave
> >
> > Dr. David Alan Gilbert (7):
> > memory: address_space_iterate
> > vhost: Move log_dirty check
> > vhost: New memory update functions
> > vhost: update_mem_cb implementation
> > vhost: Compare new and old memory lists
> > vhost: Copy updated region data into device state
> > vhost: Remove vhost_set_memory and children
> >
> > hw/virtio/trace-events | 8 +
> > hw/virtio/vhost.c | 424
> > ++++++++++++++++++++++---------------------------
> > include/exec/memory.h | 23 +++
> > memory.c | 22 +++
> > 4 files changed, 241 insertions(+), 236 deletions(-)
> >
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [RFC 1/7] memory: address_space_iterate, (continued)
- [Qemu-devel] [RFC 1/7] memory: address_space_iterate, Dr. David Alan Gilbert (git), 2017/11/29
- [Qemu-devel] [RFC 2/7] vhost: Move log_dirty check, Dr. David Alan Gilbert (git), 2017/11/29
- [Qemu-devel] [RFC 3/7] vhost: New memory update functions, Dr. David Alan Gilbert (git), 2017/11/29
- [Qemu-devel] [RFC 5/7] vhost: Compare new and old memory lists, Dr. David Alan Gilbert (git), 2017/11/29
- [Qemu-devel] [RFC 4/7] vhost: update_mem_cb implementation, Dr. David Alan Gilbert (git), 2017/11/29
- [Qemu-devel] [RFC 7/7] vhost: Remove vhost_set_memory and children, Dr. David Alan Gilbert (git), 2017/11/29
- [Qemu-devel] [RFC 6/7] vhost: Copy updated region data into device state, Dr. David Alan Gilbert (git), 2017/11/29
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates, Igor Mammedov, 2017/11/30
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates,
Dr. David Alan Gilbert <=
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates, Igor Mammedov, 2017/11/30
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates, Dr. David Alan Gilbert, 2017/11/30
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates, Igor Mammedov, 2017/11/30
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates, Dr. David Alan Gilbert, 2017/11/30
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates, Igor Mammedov, 2017/11/30
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates, Dr. David Alan Gilbert, 2017/11/30
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates, Igor Mammedov, 2017/11/30
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates, Dr. David Alan Gilbert, 2017/11/30
- Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates, Greg Kurz, 2017/11/30