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b=dPT+kdRJmrc++E4JgaDg0HvOn87ub1fN81aujiL3JuYrC+XABLmrn8IKbujtOxjox 06UW28/7RYwaB1AdZehoyv5pTGVprSBAXjHnoKbjSL+FhOIiMfHk/eazN5xF1ef35L iI2y5+BgESdTBJPjDJ0iyZWOBGh7c+XsGh6M04pYgwNZsjWk51POupKSyh33gdm0EP 45y5/jkWLrEhutdIoC4OWF5kMcmkisDNjsD7jjLCsAiCX9ZO+pgaVPoMulUmJlaGb9 4LERACYZwJIsl5lju9+IsQAyONXCgmYbWkB3p/ehSBdOllMUN3kNW2OC6dfYrgwBMJ Dugsm9vMMNdlA== Message-ID: <355d3bf3-c6bc-403e-9f19-89259d868611@kernel.org> Date: Mon, 17 Nov 2025 17:57:58 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 7/7] mm: make PT_RECLAIM depend on MMU_GATHER_RCU_TABLE_FREE && 64BIT To: Qi Zheng , will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org, dev.jain@arm.com, akpm@linux-foundation.org, ioworker0@gmail.com Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-um@lists.infradead.org, Qi Zheng References: <0a4d1e6f0bf299cafd1fc624f965bd1ca542cea8.1763117269.git.zhengqi.arch@bytedance.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <0a4d1e6f0bf299cafd1fc624f965bd1ca542cea8.1763117269.git.zhengqi.arch@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 5C19B140015 X-Stat-Signature: xx9p1u8x1nza3fmwqgqxno399n67sk3r X-Rspam-User: X-HE-Tag: 1763398686-997378 X-HE-Meta: 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 ZzKYsDtu 5t65FxOvfbJUagpMad+ZW7PrWAyt0uRfZUZZm8v89LKoU6S3nXx89Lwrq5ISdlIDrkVI3IafaO4dK+9dEWbh7ThJCPiPZ5cwOXLL6KRWGYl/wrjTwAkjOZTDkVlx+k0GZwq2BAu4s/SLHrLwgWbr7l18TW8Y6PH07CEGckjNMHWlzzp/eO2+QhbrJntuzqH8N5cGWBfAbCaaXd0tQV7caVrGVCsogHLoHX3xWTqvp0cUqEToPF+5Gg4QD0iGhBiR3p3TqphvlOHR9yqsyTIWGNRyo2L8Q/+JwuklIlIjk5eGE4jjzCMsIzjI0Xb1CtXWkysRRWrrbuUTvpTs= 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: List-Subscribe: List-Unsubscribe: On 14.11.25 12:11, Qi Zheng wrote: > From: Qi Zheng Subject: s/&&/&/ > > Make PT_RECLAIM depend on MMU_GATHER_RCU_TABLE_FREE so that PT_RECLAIM can > be enabled by default on all architectures that support > MMU_GATHER_RCU_TABLE_FREE. > > Considering that a large number of PTE page table pages (such as 100GB+) > can only be caused on a 64-bit system, let PT_RECLAIM also depend on > 64BIT. > > Signed-off-by: Qi Zheng > --- > arch/x86/Kconfig | 1 - > mm/Kconfig | 6 +----- > 2 files changed, 1 insertion(+), 6 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index eac2e86056902..96bff81fd4787 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -330,7 +330,6 @@ config X86 > select FUNCTION_ALIGNMENT_4B > imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI > select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE > - select ARCH_SUPPORTS_PT_RECLAIM if X86_64 > select ARCH_SUPPORTS_SCHED_SMT if SMP > select SCHED_SMT if SMP > select ARCH_SUPPORTS_SCHED_CLUSTER if SMP > diff --git a/mm/Kconfig b/mm/Kconfig > index a5a90b169435d..e795fbd69e50c 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -1440,14 +1440,10 @@ config ARCH_HAS_USER_SHADOW_STACK > The architecture has hardware support for userspace shadow call > stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss). > > -config ARCH_SUPPORTS_PT_RECLAIM > - def_bool n > - > config PT_RECLAIM > bool "reclaim empty user page table pages" > default y > - depends on ARCH_SUPPORTS_PT_RECLAIM && MMU && SMP > - select MMU_GATHER_RCU_TABLE_FREE > + depends on MMU_GATHER_RCU_TABLE_FREE && MMU && SMP && 64BIT Who would we have MMU_GATHER_RCU_TABLE_FREE without MMU? (can we drop the MMU part) Why do we care about SMP in the first place? (can we frop SMP) But I also wonder why we need "MMU_GATHER_RCU_TABLE_FREE && 64BIT": Would it be harmful on 32bit (sure, we might not reclaim as much, but still there is memory to be reclaimed?)? If all 64BIT support MMU_GATHER_RCU_TABLE_FREE (as you previously state), why can't we only check for 64BIT? -- Cheers David