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Tue, 11 Jan 2022 14:27:12 -0800 (PST) Date: Tue, 11 Jan 2022 15:27:08 -0700 From: Yu Zhao To: Will Deacon Cc: Andrew Morton , Linus Torvalds , Andi Kleen , Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Jesse Barnes , Johannes Weiner , Jonathan Corbet , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Rik van Riel , Vlastimil Babka , Ying Huang , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, page-reclaim@google.com, x86@kernel.org, Konstantin Kharlamov Subject: Re: [PATCH v6 1/9] mm: x86, arm64: add arch_has_hw_pte_young() Message-ID: References: <20220104202227.2903605-1-yuzhao@google.com> <20220104202227.2903605-2-yuzhao@google.com> <20220105104526.GA3015@willie-the-truck> <20220106103009.GA4420@willie-the-truck> <20220111141901.GA10338@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220111141901.GA10338@willie-the-truck> X-Rspamd-Queue-Id: 7CA711C000C X-Stat-Signature: 5b3o89kg6ncabsqbwt7pphbiuajkz5mt Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=gPYtqtvf; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf18.hostedemail.com: domain of yuzhao@google.com designates 209.85.166.41 as permitted sender) smtp.mailfrom=yuzhao@google.com X-Rspamd-Server: rspam02 X-HE-Tag: 1641940033-927517 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 Tue, Jan 11, 2022 at 02:19:02PM +0000, Will Deacon wrote: > On Fri, Jan 07, 2022 at 12:25:07AM -0700, Yu Zhao wrote: > > On Thu, Jan 06, 2022 at 10:30:09AM +0000, Will Deacon wrote: > > > On Wed, Jan 05, 2022 at 01:47:08PM -0700, Yu Zhao wrote: > > > > On Wed, Jan 05, 2022 at 10:45:26AM +0000, Will Deacon wrote: > > > > > On Tue, Jan 04, 2022 at 01:22:20PM -0700, Yu Zhao wrote: > > > > > > diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps > > > > > > index 870c39537dd0..56e4ef5d95fa 100644 > > > > > > --- a/arch/arm64/tools/cpucaps > > > > > > +++ b/arch/arm64/tools/cpucaps > > > > > > @@ -36,6 +36,7 @@ HAS_STAGE2_FWB > > > > > > HAS_SYSREG_GIC_CPUIF > > > > > > HAS_TLB_RANGE > > > > > > HAS_VIRT_HOST_EXTN > > > > > > +HW_AF > > > > > > HW_DBM > > > > > > KVM_PROTECTED_MODE > > > > > > MISMATCHED_CACHE_TYPE > > > > > > > > > > As discussed in the previous threads, we really don't need the complexity > > > > > of the additional cap for the arm64 part. Please can you just use the > > > > > existing code instead? It's both simpler and, as you say, it's equivalent > > > > > for existing hardware. > > > > > > > > > > That way, this patch just ends up being a renaming exercise and we're all > > > > > good. > > > > > > > > No, renaming alone isn't enough. A caller needs to disable preemption > > > > before calling system_has_hw_af(), and I don't think it's reasonable > > > > to ask this caller to do it on x86 as well. > > > > > > > > It seems you really prefer not to have HW_AF. So the best I can > > > > accommodate, considering other potential archs, e.g., risc-v (I do > > > > plan to provide benchmark results on risc-v, btw), is: > > > > > > > > static inline bool arch_has_hw_pte_young(bool local) > > > > { > > > > bool hw_af; > > > > > > > > if (local) { > > > > WARN_ON(preemptible()); > > > > return cpu_has_hw_af(); > > > > } > > > > > > > > preempt_disable(); > > > > hw_af = system_has_hw_af(); > > > > preempt_enable(); > > > > > > > > return hw_af; > > > > } > > > > > > > > Or please give me something else I can call without disabling > > > > preemption, sounds good? > > > > > > Sure thing, let me take a look. Do you have your series on a public git > > > tree someplace? > > > > Thanks! > > > > This patch (updated) on Gerrit: > > https://linux-mm-review.googlesource.com/c/page-reclaim/+/1500/1 > > How about folding in something like the diff below? I've basically removed > that 'bool local' argument and dropped the preemptible() check from the > arm64 code. This looks great, thanks.