From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 99FAFC4829A for ; Tue, 13 Feb 2024 16:44:15 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4TZ6by1VkWz3vYG for ; Wed, 14 Feb 2024 03:44:14 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=mark.rutland@arm.com; receiver=lists.ozlabs.org) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4TZ6bW1qpkz3cB2 for ; Wed, 14 Feb 2024 03:43:50 +1100 (AEDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 020EEDA7; Tue, 13 Feb 2024 08:44:00 -0800 (PST) Received: from FVFF77S0Q05N.cambridge.arm.com (FVFF77S0Q05N.cambridge.arm.com [10.1.36.130]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 009A73F5A1; Tue, 13 Feb 2024 08:43:14 -0800 (PST) Date: Tue, 13 Feb 2024 16:43:11 +0000 From: Mark Rutland To: Ryan Roberts Subject: Re: [PATCH v5 21/25] arm64/mm: Implement new [get_and_]clear_full_ptes() batch APIs Message-ID: References: <20240202080756.1453939-1-ryan.roberts@arm.com> <20240202080756.1453939-22-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240202080756.1453939-22-ryan.roberts@arm.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kefeng Wang , x86@kernel.org, David Hildenbrand , Catalin Marinas , Yang Shi , Dave Hansen , linux-mm@kvack.org, Andrey Ryabinin , "H. Peter Anvin" , Will Deacon , Ard Biesheuvel , Marc Zyngier , Alistair Popple , Barry Song <21cnbao@gmail.com>, Matthew Wilcox , "Aneesh Kumar K.V" , Ingo Molnar , Zi Yan , "Naveen N. Rao" , John Hubbard , Nicholas Piggin , Borislav Petkov , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, James Morse , Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, Feb 02, 2024 at 08:07:52AM +0000, Ryan Roberts wrote: > Optimize the contpte implementation to fix some of the > exit/munmap/dontneed performance regression introduced by the initial > contpte commit. Subsequent patches will solve it entirely. > > During exit(), munmap() or madvise(MADV_DONTNEED), mappings must be > cleared. Previously this was done 1 PTE at a time. But the core-mm > supports batched clear via the new [get_and_]clear_full_ptes() APIs. So > let's implement those APIs and for fully covered contpte mappings, we no > longer need to unfold the contpte. This significantly reduces unfolding > operations, reducing the number of tlbis that must be issued. > > Tested-by: John Hubbard > Signed-off-by: Ryan Roberts > --- > arch/arm64/include/asm/pgtable.h | 67 ++++++++++++++++++++++++++++++++ > arch/arm64/mm/contpte.c | 17 ++++++++ > 2 files changed, 84 insertions(+) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index c07f0d563733..ad04adb7b87f 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -965,6 +965,37 @@ static inline pte_t __ptep_get_and_clear(struct mm_struct *mm, > return pte; > } > > +static inline void __clear_full_ptes(struct mm_struct *mm, unsigned long addr, > + pte_t *ptep, unsigned int nr, int full) > +{ > + for (;;) { > + __ptep_get_and_clear(mm, addr, ptep); > + if (--nr == 0) > + break; > + ptep++; > + addr += PAGE_SIZE; > + } > +} The loop construct is a bit odd; can't this be: while (nr--) { __ptep_get_and_clear(mm, addr, ptep); ptep++; addr += PAGE_SIZE; } ... or: do { __ptep_get_and_clear(mm, addr, ptep); ptep++; addr += PAGE_SIZE; } while (--nr); ... ? Otherwise, this looks good to me. Mark. > + > +static inline pte_t __get_and_clear_full_ptes(struct mm_struct *mm, > + unsigned long addr, pte_t *ptep, > + unsigned int nr, int full) > +{ > + pte_t pte, tmp_pte; > + > + pte = __ptep_get_and_clear(mm, addr, ptep); > + while (--nr) { > + ptep++; > + addr += PAGE_SIZE; > + tmp_pte = __ptep_get_and_clear(mm, addr, ptep); > + if (pte_dirty(tmp_pte)) > + pte = pte_mkdirty(pte); > + if (pte_young(tmp_pte)) > + pte = pte_mkyoung(pte); > + } > + return pte; > +} > + > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > #define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR > static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, > @@ -1167,6 +1198,11 @@ extern pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte); > extern pte_t contpte_ptep_get_lockless(pte_t *orig_ptep); > extern void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, > pte_t *ptep, pte_t pte, unsigned int nr); > +extern void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr, > + pte_t *ptep, unsigned int nr, int full); > +extern pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm, > + unsigned long addr, pte_t *ptep, > + unsigned int nr, int full); > extern int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, > unsigned long addr, pte_t *ptep); > extern int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, > @@ -1254,6 +1290,35 @@ static inline void pte_clear(struct mm_struct *mm, > __pte_clear(mm, addr, ptep); > } > > +#define clear_full_ptes clear_full_ptes > +static inline void clear_full_ptes(struct mm_struct *mm, unsigned long addr, > + pte_t *ptep, unsigned int nr, int full) > +{ > + if (likely(nr == 1)) { > + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); > + __clear_full_ptes(mm, addr, ptep, nr, full); > + } else { > + contpte_clear_full_ptes(mm, addr, ptep, nr, full); > + } > +} > + > +#define get_and_clear_full_ptes get_and_clear_full_ptes > +static inline pte_t get_and_clear_full_ptes(struct mm_struct *mm, > + unsigned long addr, pte_t *ptep, > + unsigned int nr, int full) > +{ > + pte_t pte; > + > + if (likely(nr == 1)) { > + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); > + pte = __get_and_clear_full_ptes(mm, addr, ptep, nr, full); > + } else { > + pte = contpte_get_and_clear_full_ptes(mm, addr, ptep, nr, full); > + } > + > + return pte; > +} > + > #define __HAVE_ARCH_PTEP_GET_AND_CLEAR > static inline pte_t ptep_get_and_clear(struct mm_struct *mm, > unsigned long addr, pte_t *ptep) > @@ -1338,6 +1403,8 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, > #define set_pte __set_pte > #define set_ptes __set_ptes > #define pte_clear __pte_clear > +#define clear_full_ptes __clear_full_ptes > +#define get_and_clear_full_ptes __get_and_clear_full_ptes > #define __HAVE_ARCH_PTEP_GET_AND_CLEAR > #define ptep_get_and_clear __ptep_get_and_clear > #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG > diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c > index c85e64baf03b..80346108450b 100644 > --- a/arch/arm64/mm/contpte.c > +++ b/arch/arm64/mm/contpte.c > @@ -207,6 +207,23 @@ void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, > } > EXPORT_SYMBOL(contpte_set_ptes); > > +void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr, > + pte_t *ptep, unsigned int nr, int full) > +{ > + contpte_try_unfold_partial(mm, addr, ptep, nr); > + __clear_full_ptes(mm, addr, ptep, nr, full); > +} > +EXPORT_SYMBOL(contpte_clear_full_ptes); > + > +pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm, > + unsigned long addr, pte_t *ptep, > + unsigned int nr, int full) > +{ > + contpte_try_unfold_partial(mm, addr, ptep, nr); > + return __get_and_clear_full_ptes(mm, addr, ptep, nr, full); > +} > +EXPORT_SYMBOL(contpte_get_and_clear_full_ptes); > + > int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, > unsigned long addr, pte_t *ptep) > { > -- > 2.25.1 >