From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A61C4C43381 for ; Mon, 18 Feb 2019 19:49:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6CBC5217F9 for ; Mon, 18 Feb 2019 19:49:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="lnCZINN7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727143AbfBRTtn (ORCPT ); Mon, 18 Feb 2019 14:49:43 -0500 Received: from mail-it1-f194.google.com ([209.85.166.194]:40382 "EHLO mail-it1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726316AbfBRTtm (ORCPT ); Mon, 18 Feb 2019 14:49:42 -0500 Received: by mail-it1-f194.google.com with SMTP id i2so713727ite.5 for ; Mon, 18 Feb 2019 11:49:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=0wtsBdExeMA1wwCJ28I4aSi9QBIDjm+ySXCh9WlH+r8=; b=lnCZINN7IoVMhyN6Ibb/qlSwbfdgcKLoKqRCpyFvlLWtuAoP/FCJcQKLFGQi09gDVr 5DiPNsJ3wLufD+iHIhNZDCwwyRCLWiwKRGn/GJIg8q191GC4x6c+6wVVnjJ1WaSYzq9O 3x4YrPPt0p1oh4zkAc1KgwK83gxLOg25m+qlcqCvbwwptQv/6HSlZVPVC36c+OTBDIBy APQe2ue7roT6A2u6aQFmTgeF65aUI+pCdpn/VkyjDeN3Lu2FSg8S8Dqg0Li9uFHFoFEt Kjpz3ydKeddO0GqHPTLYFF+2YmEsV0f+vPa64ELLx8sRS1MhTdY5T/XF3M1qgBM3LpeO eB8A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=0wtsBdExeMA1wwCJ28I4aSi9QBIDjm+ySXCh9WlH+r8=; b=B8TXjlXXDSHlf1dYyT4zentR5lBF/OxlgJNGae4FI8btNRr7fsRl7/vvSaGm7AnHzf CK4HD0TjDN1gF8sT+tcR2lWprxsLZWpIqYdIB6v4o9+wJP9Z+1uYJM1TffpQM5R8zTNQ giMVmQ2ykqa2qQFuf2YbmmjoDoYlJjx6/SSeoaTC2CUOxR0VXacenQqFtYC2Wwk30aWY zAIX7hYC1AfUpoDxyGciUGXtxWS2GQodVugOU1S0SZnTTBs6m4PqYAqXXOhYkUpHLsTc k5BTGUUGiqp7eKuxrzTTcVpY7vNroy8X74Q12F4tVGvwfC3wCkrakFIdw5/okfEnONWa mAOA== X-Gm-Message-State: AHQUAuZI3CRTjihXgwykARXPEki6J2Wg8od06drcItEKp85Ge1FGTqaq 7/+OG++ry7lEYHBsuwBxXy2qVw== X-Google-Smtp-Source: AHgI3IYgK3DVojWmklhiIeoLq404ESnMMVIaR2vGDGMXORI8El0uFkQrhGihzkrV0E3C0Mg6kZr77A== X-Received: by 2002:a02:c943:: with SMTP id u3mr13451152jao.96.1550519381443; Mon, 18 Feb 2019 11:49:41 -0800 (PST) Received: from google.com ([2620:15c:183:0:a0c3:519e:9276:fc96]) by smtp.gmail.com with ESMTPSA id x17sm5606036ioa.6.2019.02.18.11.49.40 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 18 Feb 2019 11:49:40 -0800 (PST) Date: Mon, 18 Feb 2019 12:49:38 -0700 From: Yu Zhao To: Will Deacon Cc: Catalin Marinas , "Aneesh Kumar K . V" , Andrew Morton , Nick Piggin , Peter Zijlstra , Joel Fernandes , "Kirill A . Shutemov" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, mark.rutland@arm.com Subject: Re: [PATCH] arm64: mm: enable per pmd page table lock Message-ID: <20190218194938.GA184109@google.com> References: <20190214211642.2200-1-yuzhao@google.com> <20190218151223.GB16091@fuggles.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190218151223.GB16091@fuggles.cambridge.arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 18, 2019 at 03:12:23PM +0000, Will Deacon wrote: > [+Mark] > > On Thu, Feb 14, 2019 at 02:16:42PM -0700, Yu Zhao wrote: > > Switch from per mm_struct to per pmd page table lock by enabling > > ARCH_ENABLE_SPLIT_PMD_PTLOCK. This provides better granularity for > > large system. > > > > I'm not sure if there is contention on mm->page_table_lock. Given > > the option comes at no cost (apart from initializing more spin > > locks), why not enable it now. > > > > Signed-off-by: Yu Zhao > > --- > > arch/arm64/Kconfig | 3 +++ > > arch/arm64/include/asm/pgalloc.h | 12 +++++++++++- > > arch/arm64/include/asm/tlb.h | 5 ++++- > > 3 files changed, 18 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > index a4168d366127..104325a1ffc3 100644 > > --- a/arch/arm64/Kconfig > > +++ b/arch/arm64/Kconfig > > @@ -872,6 +872,9 @@ config ARCH_WANT_HUGE_PMD_SHARE > > config ARCH_HAS_CACHE_LINE_SIZE > > def_bool y > > > > +config ARCH_ENABLE_SPLIT_PMD_PTLOCK > > + def_bool y > > + > > config SECCOMP > > bool "Enable seccomp to safely compute untrusted bytecode" > > ---help--- > > diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h > > index 52fa47c73bf0..dabba4b2c61f 100644 > > --- a/arch/arm64/include/asm/pgalloc.h > > +++ b/arch/arm64/include/asm/pgalloc.h > > @@ -33,12 +33,22 @@ > > > > static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr) > > { > > - return (pmd_t *)__get_free_page(PGALLOC_GFP); > > + struct page *page; > > + > > + page = alloc_page(PGALLOC_GFP); > > + if (!page) > > + return NULL; > > + if (!pgtable_pmd_page_ctor(page)) { > > + __free_page(page); > > + return NULL; > > + } > > + return page_address(page); > > I'm a bit worried as to how this interacts with the page-table code in > arch/arm64/mm/mmu.c when pgd_pgtable_alloc is used as the allocator. It > looks like that currently always calls pgtable_page_ctor(), regardless of > level. Do we now need a separate allocator function for the PMD level? Thanks for reminding me, I never noticed this. The short answer is no. I guess pgtable_page_ctor() is used on all pud/pmd/pte entries there because it's also compatible with pud, and pmd too without this patch. So your concern is valid. Thanks again. Why my answer is no? Because I don't think the ctor matters for pgd_pgtable_alloc(). The ctor is only required for userspace page tables, and that's why we don't have it in pte_alloc_one_kernel(). AFAICT, none of the pgds (efi_mm.pgd, tramp_pg_dir and init_mm.pgd) pre-populated by pgd_pgtable_alloc() is. (I doubt we pre-populate userspace page tables in any other arch). So to avoid future confusion, we might just remove the ctor from pgd_pgtable_alloc().