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[217.140.101.70]) by mx.google.com with ESMTP id x2si459659edr.373.2019.02.13.03.21.44 for ; Wed, 13 Feb 2019 03:21:45 -0800 (PST) Received-SPF: pass (google.com: domain of catalin.marinas@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of catalin.marinas@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=catalin.marinas@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 10C951596; Wed, 13 Feb 2019 03:21:44 -0800 (PST) Received: from c02tf0j2hf1t.cambridge.arm.com (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 100593F557; Wed, 13 Feb 2019 03:21:40 -0800 (PST) Date: Wed, 13 Feb 2019 11:21:36 +0000 From: Catalin Marinas To: Anshuman Khandual Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org, kirill@shutemov.name, kirill.shutemov@linux.intel.com, vbabka@suse.cz, will.deacon@arm.com, dave.hansen@intel.com Subject: Re: [RFC 0/4] mm: Introduce lazy exec permission setting on a page Message-ID: <20190213112135.GA9296@c02tf0j2hf1t.cambridge.arm.com> References: <1550045191-27483-1-git-send-email-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1550045191-27483-1-git-send-email-anshuman.khandual@arm.com> User-Agent: Mutt/1.11.2 (2019-01-07) 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 Wed, Feb 13, 2019 at 01:36:27PM +0530, Anshuman Khandual wrote: > Setting an exec permission on a page normally triggers I-cache invalidation > which might be expensive. I-cache invalidation is not mandatory on a given > page if there is no immediate exec access on it. Non-fault modification of > user page table from generic memory paths like migration can be improved if > setting of the exec permission on the page can be deferred till actual use. > There was a performance report [1] which highlighted the problem. [...] > [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-December/620357.html FTR, this performance regression has been addressed by commit 132fdc379eb1 ("arm64: Do not issue IPIs for user executable ptes"). That said, I still think this patch series is valuable for further optimising the page migration path on arm64 (and can be extended to other architectures that currently require I/D cache maintenance for executable pages). BTW, if you are going to post new versions of this series, please include linux-arch and linux-arm-kernel. -- Catalin