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Mon, 03 Jul 2023 13:02:49 -0700 (PDT) MIME-Version: 1.0 References: <20230703135330.1865927-1-ryan.roberts@arm.com> <20230703135330.1865927-6-ryan.roberts@arm.com> In-Reply-To: <20230703135330.1865927-6-ryan.roberts@arm.com> From: Yu Zhao Date: Mon, 3 Jul 2023 14:02:13 -0600 Message-ID: Subject: Re: [PATCH v2 5/5] arm64: mm: Override arch_wants_pte_order() To: Ryan Roberts Cc: Andrew Morton , Matthew Wilcox , "Kirill A. Shutemov" , Yin Fengwei , David Hildenbrand , Catalin Marinas , Will Deacon , Anshuman Khandual , Yang Shi , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 4EFA340015 X-Stat-Signature: 6mc3m58gs9po7ospcswqded31pnri9jx X-HE-Tag: 1688414570-684196 X-HE-Meta: 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 eTzoPsAJ c6/bmGVTn8I6zcllcGcWeGPqSXMfcbIyQxAZIfIwovnDFMxftIoT5mUi+9VSBO/sgMeh40crUpMzHAJPhprChfV9mq6Nf6Lme02g0QLV8sIPdTRZd5yIdHN+z4vHW8my83cMfhZN0hUrN/Qog+0c/eJ8EB+HTqMzs8R5u5V/rKB4+2xdaK6TGvutZ7UmGuA5OVogEZS/GKirBJ7/0w+Y+owALOoNozevTuqOTPRsAuH0C5nM/bzT7gzfMJcFpypOQAJSn0A2wAGtV/nukKR4fbric5z+IAh9KCdYYsEKCWzTCNEB9rk9vgZWj/oySML5cKmXVkwvMpyk0Bm1ur7Blv8Mvxg== 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: On Mon, Jul 3, 2023 at 7:53=E2=80=AFAM Ryan Roberts = wrote: > > Define an arch-specific override of arch_wants_pte_order() so that when > FLEXIBLE_THP is enabled, large folios will be allocated for anonymous > memory with an order that is compatible with arm64's contpte mappings. > > arch_wants_pte_order() returns an order according to the following > policy: For the unhinted case, when THP is not requested for the vma, > don't allow anything bigger than 64K. This means we don't waste too much > memory. Additionally, for 4K pages this is the contpte size, and for > 16K, this is (usually) the HPA size when the uarch feature is > implemented. For the hinted case, when THP is requested for the vma, > allow the contpte size for all page size configurations; 64K for 4K, 2M > for 16K and 2M for 64K. > > Additionally, the THP and NOTHP order constants are defined using > Kconfig so it is possible to override them at build time. > > Signed-off-by: Ryan Roberts > --- > arch/arm64/Kconfig | 12 ++++++++++++ > arch/arm64/include/asm/pgtable.h | 4 ++++ > arch/arm64/mm/mmu.c | 8 ++++++++ > 3 files changed, 24 insertions(+) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 343e1e1cae10..689c5bf13dc1 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -281,6 +281,18 @@ config ARM64_CONT_PMD_SHIFT > default 5 if ARM64_16K_PAGES > default 4 > > +config ARM64_PTE_ORDER_NOTHP > + int > + default 0 if ARM64_64K_PAGES # 64K (1 page) > + default 2 if ARM64_16K_PAGES # 64K (4 pages; benefits from HPA= where HW supports it) > + default 4 if ARM64_4K_PAGES # 64K (16 pages; eligible for con= tpte-mapping) > + > +config ARM64_PTE_ORDER_THP > + int > + default 5 if ARM64_64K_PAGES # 2M (32 pages; eligible for con= tpte-mapping) > + default 7 if ARM64_16K_PAGES # 2M (128 pages; eligible for co= ntpte-mapping) > + default 4 if ARM64_4K_PAGES # 64K (16 pages; eligible for con= tpte-mapping) > + > config ARCH_MMAP_RND_BITS_MIN > default 14 if ARM64_64K_PAGES > default 16 if ARM64_16K_PAGES > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pg= table.h > index 6fd012663a01..8463d5f9f307 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -1117,6 +1117,10 @@ extern pte_t ptep_modify_prot_start(struct vm_area= _struct *vma, > extern void ptep_modify_prot_commit(struct vm_area_struct *vma, > unsigned long addr, pte_t *ptep, > pte_t old_pte, pte_t new_pte); > + > +#define arch_wants_pte_order arch_wants_pte_order > +extern int arch_wants_pte_order(struct vm_area_struct *vma); > + > #endif /* !__ASSEMBLY__ */ > > #endif /* __ASM_PGTABLE_H */ > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index af6bc8403ee4..8556c4a9b507 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1481,3 +1481,11 @@ void ptep_modify_prot_commit(struct vm_area_struct= *vma, unsigned long addr, pte > { > set_pte_at(vma->vm_mm, addr, ptep, pte); > } > + > +int arch_wants_pte_order(struct vm_area_struct *vma) > +{ > + if (hugepage_vma_check(vma, vma->vm_flags, false, true, true)) > + return CONFIG_ARM64_PTE_ORDER_THP; > + else > + return CONFIG_ARM64_PTE_ORDER_NOTHP; > +} I don't really like this because it's a mix of h/w preference and s/w policy -- from my POV, it's supposed to be the former only. The policy part should be left to core MM (arch-independent). That being said, no objection if ARM MM people think this is really what they want.