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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 1CC1DC43381 for ; Mon, 18 Feb 2019 15:12:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE133217D9 for ; Mon, 18 Feb 2019 15:12:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730750AbfBRPMe (ORCPT ); Mon, 18 Feb 2019 10:12:34 -0500 Received: from foss.arm.com ([217.140.101.70]:33058 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729038AbfBRPMe (ORCPT ); Mon, 18 Feb 2019 10:12:34 -0500 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 81ADA15AB; Mon, 18 Feb 2019 07:12:33 -0800 (PST) Received: from fuggles.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 824503F675; Mon, 18 Feb 2019 07:12:25 -0800 (PST) Date: Mon, 18 Feb 2019 15:12:23 +0000 From: Will Deacon To: Yu Zhao 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: <20190218151223.GB16091@fuggles.cambridge.arm.com> References: <20190214211642.2200-1-yuzhao@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190214211642.2200-1-yuzhao@google.com> User-Agent: Mutt/1.11.1+86 (6f28e57d73f2) () Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [+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? Will