From: "Michael S. Tsirkin" <mst@redhat.com>
To: Alexander Duyck <alexander.duyck@gmail.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, rkrcmar@redhat.com,
alexander.h.duyck@linux.intel.com, x86@kernel.org,
mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
pbonzini@redhat.com, tglx@linutronix.de,
akpm@linux-foundation.org
Subject: Re: [RFC PATCH 4/4] mm: Add merge page notifier
Date: Sat, 9 Feb 2019 19:57:31 -0500 [thread overview]
Message-ID: <20190209195325-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20190204181558.12095.83484.stgit@localhost.localdomain>
On Mon, Feb 04, 2019 at 10:15:58AM -0800, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
>
> Because the implementation was limiting itself to only providing hints on
> pages huge TLB order sized or larger we introduced the possibility for free
> pages to slip past us because they are freed as something less then
> huge TLB in size and aggregated with buddies later.
>
> To address that I am adding a new call arch_merge_page which is called
> after __free_one_page has merged a pair of pages to create a higher order
> page. By doing this I am able to fill the gap and provide full coverage for
> all of the pages huge TLB order or larger.
>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Looks like this will be helpful whenever active free page
hints are added. So I think it's a good idea to
add a hook.
However, could you split adding the hook to a separate
patch from the KVM hypercall based implementation?
Then e.g. Nilal's patches could reuse it too.
> ---
> arch/x86/include/asm/page.h | 12 ++++++++++++
> arch/x86/kernel/kvm.c | 28 ++++++++++++++++++++++++++++
> include/linux/gfp.h | 4 ++++
> mm/page_alloc.c | 2 ++
> 4 files changed, 46 insertions(+)
>
> diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
> index 4487ad7a3385..9540a97c9997 100644
> --- a/arch/x86/include/asm/page.h
> +++ b/arch/x86/include/asm/page.h
> @@ -29,6 +29,18 @@ 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);
> }
> +
> +struct zone;
> +
> +#define HAVE_ARCH_MERGE_PAGE
> +void __arch_merge_page(struct zone *zone, struct page *page,
> + unsigned int order);
> +static inline void arch_merge_page(struct zone *zone, struct page *page,
> + unsigned int order)
> +{
> + if (static_branch_unlikely(&pv_free_page_hint_enabled))
> + __arch_merge_page(zone, page, order);
> +}
> #endif
>
> #include <linux/range.h>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 09c91641c36c..957bb4f427bb 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -785,6 +785,34 @@ void __arch_free_page(struct page *page, unsigned int order)
> PAGE_SIZE << order);
> }
>
> +void __arch_merge_page(struct zone *zone, struct page *page,
> + unsigned int order)
> +{
> + /*
> + * The merging logic has merged a set of buddies up to the
> + * KVM_PV_UNUSED_PAGE_HINT_MIN_ORDER. Since that is the case, take
> + * advantage of this moment to notify the hypervisor of the free
> + * memory.
> + */
> + if (order != KVM_PV_UNUSED_PAGE_HINT_MIN_ORDER)
> + return;
> +
> + /*
> + * Drop zone lock while processing the hypercall. This
> + * should be safe as the page has not yet been added
> + * to the buddy list as of yet and all the pages that
> + * were merged have had their buddy/guard flags cleared
> + * and their order reset to 0.
> + */
> + spin_unlock(&zone->lock);
> +
> + kvm_hypercall2(KVM_HC_UNUSED_PAGE_HINT, page_to_phys(page),
> + PAGE_SIZE << order);
> +
> + /* reacquire lock and resume freeing memory */
> + spin_lock(&zone->lock);
> +}
> +
> #ifdef CONFIG_PARAVIRT_SPINLOCKS
>
> /* Kick a cpu by its apicid. Used to wake up a halted vcpu */
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index fdab7de7490d..4746d5560193 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -459,6 +459,10 @@ static inline struct zonelist *node_zonelist(int nid, gfp_t flags)
> #ifndef HAVE_ARCH_FREE_PAGE
> static inline void arch_free_page(struct page *page, int order) { }
> #endif
> +#ifndef HAVE_ARCH_MERGE_PAGE
> +static inline void
> +arch_merge_page(struct zone *zone, struct page *page, int order) { }
> +#endif
> #ifndef HAVE_ARCH_ALLOC_PAGE
> static inline void arch_alloc_page(struct page *page, int order) { }
> #endif
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index c954f8c1fbc4..7a1309b0b7c5 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -913,6 +913,8 @@ static inline void __free_one_page(struct page *page,
> page = page + (combined_pfn - pfn);
> pfn = combined_pfn;
> order++;
> +
> + arch_merge_page(zone, page, order);
> }
> if (max_order < MAX_ORDER) {
> /* If we are here, it means order is >= pageblock_order.
next prev parent reply other threads:[~2019-02-10 1:01 UTC|newest]
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
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 [this message]
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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