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[209.132.183.28]) by mx.google.com with ESMTPS id q12si205322qvd.64.2019.02.11.10.09.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Feb 2019 10:09:49 -0800 (PST) Received-SPF: pass (google.com: domain of nitesh@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of nitesh@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=nitesh@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 74A21A82C; Mon, 11 Feb 2019 18:09:48 +0000 (UTC) Received: from [10.18.17.32] (dhcp-17-32.bos.redhat.com [10.18.17.32]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CF3D560C6B; Mon, 11 Feb 2019 18:09:42 +0000 (UTC) From: Nitesh Narayan Lal To: "Michael S. Tsirkin" Cc: Alexander Duyck , 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 References: <20190204181118.12095.38300.stgit@localhost.localdomain> <20190204181558.12095.83484.stgit@localhost.localdomain> <20190209195325-mutt-send-email-mst@kernel.org> <7fcb61d6-64f0-f3ae-5e32-0e9f587fdd49@redhat.com> <20190211091623-mutt-send-email-mst@kernel.org> <20190211123815-mutt-send-email-mst@kernel.org> Organization: Red Hat Inc, Message-ID: Date: Mon, 11 Feb 2019 13:09:40 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190211123815-mutt-send-email-mst@kernel.org> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="c5ocnaYNnPDVZBKYZaAjEHZbi4GrRb2Dg" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Mon, 11 Feb 2019 18:09:48 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --c5ocnaYNnPDVZBKYZaAjEHZbi4GrRb2Dg Content-Type: multipart/mixed; boundary="d7qNngcBe97AVwp8UkiKrXYgbgVRREpbY"; protected-headers="v1" From: Nitesh Narayan Lal To: "Michael S. Tsirkin" Cc: Alexander Duyck , 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 Message-ID: Subject: Re: [RFC PATCH 4/4] mm: Add merge page notifier --d7qNngcBe97AVwp8UkiKrXYgbgVRREpbY Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 2/11/19 12:41 PM, Michael S. Tsirkin wrote: > On Mon, Feb 11, 2019 at 11:24:02AM -0500, Nitesh Narayan Lal wrote: >> On 2/11/19 9:17 AM, Michael S. Tsirkin wrote: >>> On Mon, Feb 11, 2019 at 08:30:03AM -0500, Nitesh Narayan Lal wrote: >>>> On 2/9/19 7:57 PM, Michael S. Tsirkin wrote: >>>>> On Mon, Feb 04, 2019 at 10:15:58AM -0800, Alexander Duyck wrote: >>>>>> From: Alexander Duyck >>>>>> >>>>>> Because the implementation was limiting itself to only providing h= ints 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 the= n >>>>>> huge TLB in size and aggregated with buddies later. >>>>>> >>>>>> To address that I am adding a new call arch_merge_page which is ca= lled >>>>>> after __free_one_page has merged a pair of pages to create a highe= r order >>>>>> page. By doing this I am able to fill the gap and provide full cov= erage for >>>>>> all of the pages huge TLB order or larger. >>>>>> >>>>>> Signed-off-by: Alexander Duyck = >>>>> 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. >>>> With the current design of my patch-set, if I use this hook to repor= t >>>> free pages. I will end up making redundant hints for the same pfns. >>>> >>>> This is because the pages once freed by the host, are returned back = to >>>> the buddy. >>> Suggestions on how you'd like to fix this? You do need this if >>> you introduce a size cut-off right? >> I do, there are two ways to go about it. >> >> One is to=C2=A0 use this and have a flag in the page structure indicat= ing >> whether that page has been freed/used or not. > Not sure what do you mean. The refcount does this right? I meant a flag using which I could determine whether a PFN has been already freed by the host or not. This is to avoid repetitive free. > >> Though I am not sure if >> this will be acceptable upstream. >> Second is to find another place to invoke guest_free_page() post buddy= >> merging. > Might be easier. > >>>>>> --- >>>>>> 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/pa= ge.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 >>>>>> =20 >>>>>> #include >>>>>> 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, unsi= gned int order) >>>>>> PAGE_SIZE << order); >>>>>> } >>>>>> =20 >>>>>> +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, ta= ke >>>>>> + * advantage of this moment to notify the hypervisor of the free= >>>>>> + * memory. >>>>>> + */ >>>>>> + if (order !=3D 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 >>>>>> =20 >>>>>> /* 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 =3D page + (combined_pfn - pfn); >>>>>> pfn =3D combined_pfn; >>>>>> order++; >>>>>> + >>>>>> + arch_merge_page(zone, page, order); >>>>>> } >>>>>> if (max_order < MAX_ORDER) { >>>>>> /* If we are here, it means order is >=3D pageblock_order. >>>> --=20 >>>> Regards >>>> Nitesh >>>> >>> >> --=20 >> Regards >> Nitesh >> > > --=20 Regards Nitesh --d7qNngcBe97AVwp8UkiKrXYgbgVRREpbY-- --c5ocnaYNnPDVZBKYZaAjEHZbi4GrRb2Dg Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkXcoRVGaqvbHPuAGo4ZA3AYyozkFAlxhumQACgkQo4ZA3AYy oznUwQ/+Kqi1R0b3vCG91aTEPof4m7+/hWZAKTAtsmxfAFcIF51vEft0suA8xKZZ qBfrn4KmUlCDMEEdkwuY1G2HwuKvo4KMxXVnmIWfl6PicT3S3Hi3sjItPB08a4ou bINoBIjG3tawHsuEhKGWcLr0wc6uD3gcZhJWTwqLktFRbxLW95uUGe8pJTJibLIF zFZcRczMONVkhScgJZ5oUnmvUr8nRPlCVPlRJPNu3rkzP8ks55Af5jQdhxWvhFeS xf6DdsOzLcqjUAX7FMt5sUeiSv7pdl+8+8z91qDfYjAC3B/xLuQ6Q8SoMO2CR2AY hiE31mJMq0WLnsJqPHPhT6hBSYd/EuyhMGu0NYFjjGTuvI/CgfJ2wOYkQpb/dBX6 wsY/O/OnRb6fPt3rNW3KhT4ASV/+TPVIu70UK1EAVJER72e7pIZAcyg6R5BiMOqH T+X8d4WJBpN9Kp5KQBpo3I4iTdSSGqpwWxhOMpmGveZpb7cpZXVykECYHpDKQdAE PCnJfBi/q53LV4emdQOWeGZcjJwp8SE6ZfkSw7T1cnVZ1HcfDwxMHVgGeE5085ZT JbDgkJI82pGJ778gOKryt0vraR07xgXdgtJv9jJDCPfOVm7oyT5Oh8iWwSWVeHPI Li7uZYIYRIDpdUrIVQ8vitiq0YYNAmPBpU/1uinRE+gm2jLhogQ= =3dJa -----END PGP SIGNATURE----- --c5ocnaYNnPDVZBKYZaAjEHZbi4GrRb2Dg--