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Mon, 03 Jul 2023 20:02:43 -0700 (PDT) MIME-Version: 1.0 References: <20230703135330.1865927-1-ryan.roberts@arm.com> <20230703135330.1865927-4-ryan.roberts@arm.com> In-Reply-To: From: Yu Zhao Date: Mon, 3 Jul 2023 21:02:07 -0600 Message-ID: Subject: Re: [PATCH v2 3/5] mm: Default implementation of arch_wants_pte_order() To: "Yin, Fengwei" Cc: Ryan Roberts , Andrew Morton , Matthew Wilcox , "Kirill A. Shutemov" , 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-Rspamd-Queue-Id: 0D601C0014 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 57tj4xsnug4rzanqwf4u9gogho8dejah X-HE-Tag: 1688439764-458081 X-HE-Meta: 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 OPMB7AQv Z+NP+CdHmYBLkkZ4GFP3twqHWfWSAKAHJhF70eWhx2vcxjHoFkyc6a+kKQbDILRcrbizBnKnuo7t1yKBWiUZEbhLA1GutvDBt07jD2SQfOJ2sihE0KD8c8jiS1sXe6jmJBZperhWhFkK8ITYIThTGmqID++nokFKUm+az3koomH8qw8wVEsUlDCnuBvBJXMOHVfYZRr6YMrtYotu+sJUH3/aF5n9e+U4DpRkWzKO3Mei9DRNZ2toDGJQ20cVD+m5gyDLku31lrMUhU/5vAyx170T1N38D8BHqur/rfEbVITwWZrcfxRNaHR8CoNbwH1+uQ8tzMnHYPnUMjAhEWU6kfM9quwnknbcycVkqKUaFo8hMSF8= 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 8:23=E2=80=AFPM Yin, Fengwei = wrote: > > > > On 7/3/2023 9:53 PM, Ryan Roberts wrote: > > arch_wants_pte_order() can be overridden by the arch to return the > > preferred folio order for pte-mapped memory. This is useful as some > > architectures (e.g. arm64) can coalesce TLB entries when the physical > > memory is suitably contiguous. > > > > The first user for this hint will be FLEXIBLE_THP, which aims to > > allocate large folios for anonymous memory to reduce page faults and > > other per-page operation costs. > > > > Here we add the default implementation of the function, used when the > > architecture does not define it, which returns the order corresponding > > to 64K. > > > > Signed-off-by: Ryan Roberts > > --- > > include/linux/pgtable.h | 13 +++++++++++++ > > 1 file changed, 13 insertions(+) > > > > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > > index a661a17173fa..f7e38598f20b 100644 > > --- a/include/linux/pgtable.h > > +++ b/include/linux/pgtable.h > > @@ -13,6 +13,7 @@ > > #include > > #include > > #include > > +#include > > > > #if 5 - defined(__PAGETABLE_P4D_FOLDED) - defined(__PAGETABLE_PUD_FOLD= ED) - \ > > defined(__PAGETABLE_PMD_FOLDED) !=3D CONFIG_PGTABLE_LEVELS > > @@ -336,6 +337,18 @@ static inline bool arch_has_hw_pte_young(void) > > } > > #endif > > > > +#ifndef arch_wants_pte_order > > +/* > > + * Returns preferred folio order for pte-mapped memory. Must be in ran= ge [0, > > + * PMD_SHIFT-PAGE_SHIFT) and must not be order-1 since THP requires la= rge folios > > + * to be at least order-2. > > + */ > > +static inline int arch_wants_pte_order(struct vm_area_struct *vma) > > +{ > > + return ilog2(SZ_64K >> PAGE_SHIFT); > Default value which is not related with any silicon may be: PAGE_ALLOC_CO= STLY_ORDER? > > Also, current pcp list support cache page with order 0...PAGE_ALLOC_COSTL= Y_ORDER, 9. > If the pcp could cover the page, the pressure to zone lock will be reduce= d by pcp. The value of PAGE_ALLOC_COSTLY_ORDER is reasonable but again it's a s/w policy not a h/w preference. Besides, I don't think we can include mmzone.h in pgtable.h.