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

From	David Hildenbrand <david@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v11 4/6] mm: function to offer a page block on the free list
Date	2017-06-20 18:50 +0200
Message-ID	<tUuvM-2D0-15@gated-at.bofh.it> (permalink)
References	<tQpEl-qv-1@gated-at.bofh.it> <tQpEl-qv-7@gated-at.bofh.it> <tRyme-3aL-9@gated-at.bofh.it> <tUuvM-2D0-1@gated-at.bofh.it>
Organization	Red Hat GmbH

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On 20.06.2017 18:44, Rik van Riel wrote:
> On Mon, 2017-06-12 at 07:10 -0700, Dave Hansen wrote:
> 
>> The hypervisor is going to throw away the contents of these pages,
>> right?  As soon as the spinlock is released, someone can allocate a
>> page, and put good data in it.  What keeps the hypervisor from
>> throwing
>> away good data?
> 
> That looks like it may be the wrong API, then?
> 
> We already have hooks called arch_free_page and
> arch_alloc_page in the VM, which are called when
> pages are freed, and allocated, respectively.
> 
> 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.

-- 

Thanks,

David

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

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