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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6c162db0986sm10643056d6.97.2024.08.22.12.16.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Aug 2024 12:16:58 -0700 (PDT) Date: Thu, 22 Aug 2024 15:16:55 -0400 From: Peter Xu To: LEROY Christophe Cc: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Vlastimil Babka , David Hildenbrand , Oscar Salvador , "linux-s390@vger.kernel.org" , Andrew Morton , Matthew Wilcox , Dan Williams , Michal Hocko , "linux-riscv@lists.infradead.org" , "sparclinux@vger.kernel.org" , Alex Williamson , Jason Gunthorpe , "x86@kernel.org" , Alistair Popple , "linuxppc-dev@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" , Ryan Roberts , Hugh Dickins , Axel Rasmussen Subject: Re: [PATCH RFC 2/6] mm: PGTABLE_HAS_P[MU]D_LEAVES config options Message-ID: References: <20240717220219.3743374-1-peterx@redhat.com> <20240717220219.3743374-3-peterx@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Aug 22, 2024 at 05:22:03PM +0000, LEROY Christophe wrote: > > > Le 18/07/2024 à 00:02, Peter Xu a écrit : > > Introduce two more sub-options for PGTABLE_HAS_HUGE_LEAVES: > > > > - PGTABLE_HAS_PMD_LEAVES: set when there can be PMD mappings > > - PGTABLE_HAS_PUD_LEAVES: set when there can be PUD mappings > > > > It will help to identify whether the current build may only want PMD > > helpers but not PUD ones, as these sub-options will also check against the > > arch support over HAVE_ARCH_TRANSPARENT_HUGEPAGE[_PUD]. > > > > Note that having them depend on HAVE_ARCH_TRANSPARENT_HUGEPAGE[_PUD] is > > still some intermediate step. The best way is to have an option say > > "whether arch XXX supports PMD/PUD mappings" and so on. However let's > > leave that for later as that's the easy part. So far, we use these options > > to stably detect per-arch huge mapping support. > > > > Signed-off-by: Peter Xu > > --- > > include/linux/huge_mm.h | 10 +++++++--- > > mm/Kconfig | 6 ++++++ > > 2 files changed, 13 insertions(+), 3 deletions(-) > > > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > > index 711632df7edf..37482c8445d1 100644 > > --- a/include/linux/huge_mm.h > > +++ b/include/linux/huge_mm.h > > @@ -96,14 +96,18 @@ extern struct kobj_attribute thpsize_shmem_enabled_attr; > > #define thp_vma_allowable_order(vma, vm_flags, tva_flags, order) \ > > (!!thp_vma_allowable_orders(vma, vm_flags, tva_flags, BIT(order))) > > > > -#ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES > > -#define HPAGE_PMD_SHIFT PMD_SHIFT > > +#ifdef CONFIG_PGTABLE_HAS_PUD_LEAVES > > #define HPAGE_PUD_SHIFT PUD_SHIFT > > #else > > -#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) > > #define HPAGE_PUD_SHIFT ({ BUILD_BUG(); 0; }) > > #endif > > > > +#ifdef CONFIG_PGTABLE_HAS_PMD_LEAVES > > +#define HPAGE_PMD_SHIFT PMD_SHIFT > > +#else > > +#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) > > +#endif > > + > > #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT) > > #define HPAGE_PMD_NR (1< > #define HPAGE_PMD_MASK (~(HPAGE_PMD_SIZE - 1)) > > diff --git a/mm/Kconfig b/mm/Kconfig > > index 60796402850e..2dbdc088dee8 100644 > > --- a/mm/Kconfig > > +++ b/mm/Kconfig > > @@ -860,6 +860,12 @@ endif # TRANSPARENT_HUGEPAGE > > config PGTABLE_HAS_HUGE_LEAVES > > def_bool TRANSPARENT_HUGEPAGE || HUGETLB_PAGE > > > > +config PGTABLE_HAS_PMD_LEAVES > > + def_bool HAVE_ARCH_TRANSPARENT_HUGEPAGE && PGTABLE_HAS_HUGE_LEAVES > > + > > +config PGTABLE_HAS_PUD_LEAVES > > + def_bool HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD && PGTABLE_HAS_HUGE_LEAVES > > + > > What if an architecture has hugepages at PMD and/or PUD level and > doesn't support THP ? What's the arch to be discussed here? The whole purpose of this series so far is trying to make some pmd/pud helpers that only defined with CONFIG_THP=on to be available even if not. It means this series alone (or any future plan) shouldn't affect any arch that has CONFIG_THP=off always. But logically I think we should need some config option just to say "this arch supports pmd mappings" indeed, even if CONFIG_THP=off. When that's there, we should perhaps add that option into this equation so PGTABLE_HAS_*_LEAVES will also be selected in that case. -- Peter Xu