From: "Michael S. Tsirkin" <mst@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: wei.w.wang@intel.com, virtio-dev@lists.oasis-open.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
virtualization <virtualization@lists.linux-foundation.org>,
KVM list <kvm@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
Michal Hocko <mhocko@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Paolo Bonzini <pbonzini@redhat.com>,
liliang.opensource@gmail.com, yang.zhang.wz@gmail.com,
quan.xu0@gmail.com, nilal@redhat.com,
Rik van Riel <riel@redhat.com>,
peterx@redhat.com
Subject: Re: [PATCH v33 1/4] mm: add a function to get free page blocks
Date: Wed, 27 Jun 2018 22:07:02 +0300 [thread overview]
Message-ID: <20180627220402-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CA+55aFwFpDPvfL=KPdabO-x1r0FnwpfPk5oN8+e01TKqAPNYbw@mail.gmail.com>
On Wed, Jun 27, 2018 at 09:05:39AM -0700, Linus Torvalds wrote:
> [ Sorry for slow reply, my travels have made a mess of my inbox ]
>
> On Mon, Jun 25, 2018 at 6:55 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > Linus, do you think it would be ok to have get_from_free_page_list
> > actually pop entries from the free list and use them as the buffer
> > to store PAs?
>
> Honestly, what I think the best option would be is to get rid of this
> interface *entirely*, and just have the balloon code do
>
> #define GFP_MINFLAGS (__GFP_NORETRY | __GFP_NOWARN |
> __GFP_THISNODE | __GFP_NOMEMALLOC)
>
> struct page *page = alloc_pages(GFP_MINFLAGS, MAX_ORDER-1);
>
> which is not a new interface, and simply removes the max-order page
> from the list if at all possible.
>
> The above has the advantage of "just working", and not having any races.
>
> Now, because you don't want to necessarily *entirely* deplete the max
> order, I'd suggest that the *one* new interface you add is just a "how
> many max-order pages are there" interface. So then you can query
> (either before or after getting the max-order page) just how many of
> them there were and whether you want to give that page back.
>
> Notice? No need for any page lists or physical addresses. No races. No
> complex new functions.
>
> The physical address you can just get from the "struct page" you got.
>
> And if you run out of memory because of getting a page, you get all
> the usual "hey, we ran out of memory" responses..
>
> Wouldn't the above be sufficient?
>
> Linus
I think so, thanks!
Wei, to put it in balloon terms, I think there's one thing we missed: if
you do manage to allocate a page, and you don't have a use for it, then
hey, you can just give it to the host because you know it's free - you
are going to return it to the free list.
--
MST
next prev parent reply other threads:[~2018-06-27 19:07 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-15 4:43 [PATCH v33 0/4] Virtio-balloon: support free page reporting Wei Wang
2018-06-15 4:43 ` [PATCH v33 1/4] mm: add a function to get free page blocks Wei Wang
2018-06-15 23:08 ` Linus Torvalds
2018-06-16 1:19 ` Wang, Wei W
2018-06-26 1:55 ` Michael S. Tsirkin
2018-06-27 16:05 ` Linus Torvalds
2018-06-27 19:07 ` Michael S. Tsirkin [this message]
2018-06-28 8:39 ` Wei Wang
2018-06-16 4:50 ` Matthew Wilcox
2018-06-17 0:07 ` Wang, Wei W
2018-06-18 2:16 ` Michael S. Tsirkin
2018-06-15 4:43 ` [PATCH v33 2/4] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT Wei Wang
2018-06-15 11:42 ` Michael S. Tsirkin
2018-06-15 14:11 ` Wang, Wei W
2018-06-15 14:29 ` Michael S. Tsirkin
2018-06-16 1:09 ` Wang, Wei W
2018-06-18 2:28 ` Michael S. Tsirkin
2018-06-19 1:06 ` [virtio-dev] " Wang, Wei W
2018-06-19 3:05 ` Michael S. Tsirkin
2018-06-19 12:13 ` Wei Wang
2018-06-19 14:43 ` Michael S. Tsirkin
2018-06-20 9:11 ` Wang, Wei W
2018-06-20 14:14 ` Michael S. Tsirkin
2018-06-15 4:43 ` [PATCH v33 3/4] mm/page_poison: expose page_poisoning_enabled to kernel modules Wei Wang
2018-06-15 4:43 ` [PATCH v33 4/4] virtio-balloon: VIRTIO_BALLOON_F_PAGE_POISON Wei Wang
2018-06-15 11:29 ` [PATCH v33 0/4] Virtio-balloon: support free page reporting Michael S. Tsirkin
2018-06-15 14:28 ` Wang, Wei W
2018-06-15 14:38 ` Michael S. Tsirkin
2018-06-15 19:21 ` Luiz Capitulino
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