From: Nadav Amit <nadav.amit@gmail.com>
To: Alexander Duyck <alexander.duyck@gmail.com>
Cc: Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kvm list <kvm@vger.kernel.org>, Radim Krcmar <rkrcmar@redhat.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
X86 ML <x86@kernel.org>, Ingo Molnar <mingo@redhat.com>,
bp@alien8.de, hpa@zytor.com, pbonzini@redhat.com,
tglx@linutronix.de, akpm@linux-foundation.org
Subject: Re: [RFC PATCH 3/4] kvm: Add guest side support for free memory hints
Date: Mon, 4 Feb 2019 15:00:18 -0800
Message-ID: <4E64E8CA-6741-47DF-87DE-88D01B01B15D@gmail.com> (raw)
In-Reply-To: <20190204181552.12095.46287.stgit@localhost.localdomain>
> On Feb 4, 2019, at 10:15 AM, Alexander Duyck <alexander.duyck@gmail.com> wrote:
>
> From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
>
> Add guest support for providing free memory hints to the KVM hypervisor for
> freed pages huge TLB size or larger. I am restricting the size to
> huge TLB order and larger because the hypercalls are too expensive to be
> performing one per 4K page. Using the huge TLB order became the obvious
> choice for the order to use as it allows us to avoid fragmentation of higher
> order memory on the host.
>
> I have limited the functionality so that it doesn't work when page
> poisoning is enabled. I did this because a write to the page after doing an
> MADV_DONTNEED would effectively negate the hint, so it would be wasting
> cycles to do so.
>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> ---
> arch/x86/include/asm/page.h | 13 +++++++++++++
> arch/x86/kernel/kvm.c | 23 +++++++++++++++++++++++
> 2 files changed, 36 insertions(+)
>
> diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
> index 7555b48803a8..4487ad7a3385 100644
> --- a/arch/x86/include/asm/page.h
> +++ b/arch/x86/include/asm/page.h
> @@ -18,6 +18,19 @@
>
> struct page;
>
> +#ifdef CONFIG_KVM_GUEST
> +#include <linux/jump_label.h>
> +extern struct static_key_false pv_free_page_hint_enabled;
> +
> +#define HAVE_ARCH_FREE_PAGE
> +void __arch_free_page(struct page *page, unsigned int order);
> +static inline void arch_free_page(struct page *page, unsigned int order)
> +{
> + if (static_branch_unlikely(&pv_free_page_hint_enabled))
> + __arch_free_page(page, order);
> +}
> +#endif
This patch and the following one assume that only KVM should be able to hook
to these events. I do not think it is appropriate for __arch_free_page() to
effectively mean “kvm_guest_free_page()”.
Is it possible to use the paravirt infrastructure for this feature,
similarly to other PV features? It is not the best infrastructure, but at least
it is hypervisor-neutral.
next prev parent reply index
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-04 18:15 [RFC PATCH 0/4] kvm: Report unused guest pages to host Alexander Duyck
2019-02-04 18:15 ` [RFC PATCH 1/4] madvise: Expose ability to set dontneed from kernel Alexander Duyck
2019-02-04 18:15 ` [RFC PATCH 2/4] kvm: Add host side support for free memory hints Alexander Duyck
2019-02-10 0:44 ` Michael S. Tsirkin
2019-02-11 17:34 ` Alexander Duyck
2019-02-11 17:36 ` Michael S. Tsirkin
2019-02-11 17:41 ` Dave Hansen
2019-02-11 17:48 ` Michael S. Tsirkin
2019-02-11 18:30 ` Alexander Duyck
2019-02-11 19:24 ` Michael S. Tsirkin
2019-02-04 18:15 ` [RFC PATCH 3/4] kvm: Add guest " Alexander Duyck
2019-02-04 19:44 ` Dave Hansen
2019-02-04 20:42 ` Alexander Duyck
2019-02-04 23:00 ` Nadav Amit [this message]
2019-02-04 23:37 ` Alexander Duyck
2019-02-05 0:03 ` Nadav Amit
2019-02-05 0:16 ` Alexander Duyck
2019-02-05 1:46 ` Nadav Amit
2019-02-05 18:09 ` Alexander Duyck
2019-02-07 18:21 ` Luiz Capitulino
2019-02-07 18:44 ` Alexander Duyck
2019-02-07 20:02 ` Luiz Capitulino
2019-02-08 21:05 ` Nitesh Narayan Lal
2019-02-08 21:31 ` Alexander Duyck
2019-02-10 0:49 ` Michael S. Tsirkin
2019-02-11 16:31 ` Alexander Duyck
2019-02-11 17:36 ` Michael S. Tsirkin
2019-02-11 18:10 ` Alexander Duyck
2019-02-11 19:54 ` Michael S. Tsirkin
2019-02-11 21:00 ` Alexander Duyck
2019-02-11 22:52 ` Michael S. Tsirkin
[not found] ` <94462313ccd927d25675f69de459456cf066c1a2.camel@linux.intel.com>
2019-02-12 0:34 ` Michael S. Tsirkin
2019-02-11 17:48 ` Dave Hansen
2019-02-11 17:58 ` Michael S. Tsirkin
2019-02-11 18:19 ` Dave Hansen
2019-02-11 19:56 ` Michael S. Tsirkin
2019-02-04 18:15 ` [RFC PATCH 4/4] mm: Add merge page notifier Alexander Duyck
2019-02-04 19:40 ` Dave Hansen
2019-02-04 19:51 ` Alexander Duyck
2019-02-10 0:57 ` Michael S. Tsirkin
2019-02-11 13:30 ` Nitesh Narayan Lal
2019-02-11 14:17 ` Michael S. Tsirkin
2019-02-11 16:24 ` Nitesh Narayan Lal
2019-02-11 17:41 ` Michael S. Tsirkin
2019-02-11 18:09 ` Nitesh Narayan Lal
2019-02-11 6:40 ` Aaron Lu
2019-02-11 15:58 ` Alexander Duyck
2019-02-12 2:09 ` Aaron Lu
2019-02-12 17:20 ` Alexander Duyck
2019-02-04 18:19 ` [RFC PATCH QEMU] i386/kvm: Enable paravirtual unused page hint mechanism Alexander Duyck
2019-02-05 17:25 ` [RFC PATCH 0/4] kvm: Report unused guest pages to host Nitesh Narayan Lal
2019-02-05 18:43 ` Alexander Duyck
2019-02-07 14:48 ` Nitesh Narayan Lal
2019-02-07 16:56 ` Alexander Duyck
2019-02-10 0:51 ` Michael S. Tsirkin
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