Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1670982

Re: [PATCH v11 4/6] mm: function to offer a page block on the free list

Show all headers | View raw

[Multipart message — attachments visible in raw view] - view raw

On Tue, 2017-06-20 at 18:49 +0200, David Hildenbrand wrote:
> On 20.06.2017 18:44, Rik van Riel wrote:

> > Nitesh Lal (on the CC list) is working on a way
> > to efficiently batch recently freed pages for
> > free page hinting to the hypervisor.
> > 
> > If that is done efficiently enough (eg. with
> > MADV_FREE on the hypervisor side for lazy freeing,
> > and lazy later re-use of the pages), do we still
> > need the harder to use batch interface from this
> > patch?
> > 
> 
> David's opinion incoming:
> 
> No, I think proper free page hinting would be the optimum solution,
> if
> done right. This would avoid the batch interface and even turn
> virtio-balloon in some sense useless.

I agree with that.  Let me go into some more detail of
what Nitesh is implementing:

1) In arch_free_page, the being-freed page is added
   to a per-cpu set of freed pages.
2) Once that set is full, arch_free_pages goes into a
   slow path, which:
   2a) Iterates over the set of freed pages, and
   2b) Checks whether they are still free, and
   2c) Adds the still free pages to a list that is
       to be passed to the hypervisor, to be MADV_FREEd.
   2d) Makes that hypercall.

Meanwhile all arch_alloc_pages has to do is make sure it
does not allocate a page while it is currently being
MADV_FREEd on the hypervisor side.

The code Wei is working on looks like it could be 
suitable for steps (2c) and (2d) above. Nitesh already
has code for steps 1 through 2b.

-- 
All rights reversed

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list Rik van Riel <riel@redhat.com> - 2017-06-20 18:50 +0200
  Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list David Hildenbrand <david@redhat.com> - 2017-06-20 18:50 +0200
    Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list Rik van Riel <riel@redhat.com> - 2017-06-20 19:30 +0200
      Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list "Michael S. Tsirkin" <mst@redhat.com> - 2017-06-20 20:30 +0200
        Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list Rik van Riel <riel@redhat.com> - 2017-06-20 22:00 +0200
          Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list "Michael S. Tsirkin" <mst@redhat.com> - 2017-06-21 14:50 +0200
      Re: [Qemu-devel] [PATCH v11 4/6] mm: function to offer a page block  on the free list Wei Wang <wei.w.wang@intel.com> - 2017-06-21 10:40 +0200
    Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list "Michael S. Tsirkin" <mst@redhat.com> - 2017-06-20 20:20 +0200
      Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list "Michael S. Tsirkin" <mst@redhat.com> - 2017-06-20 21:00 +0200
        Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list David Hildenbrand <david@redhat.com> - 2017-06-20 21:10 +0200
      Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list David Hildenbrand <david@redhat.com> - 2017-06-20 21:00 +0200
    Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list Christian Borntraeger <borntraeger@de.ibm.com> - 2017-06-21 15:00 +0200
      Re: [PATCH v11 4/6] mm: function to offer a page block on the free  list David Hildenbrand <david@redhat.com> - 2017-06-21 15:50 +0200

csiph-web