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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 67F81C43381 for ; Mon, 11 Mar 2019 12:12:49 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 372582075C for ; Mon, 11 Mar 2019 12:12:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="RX3ejb+z" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 372582075C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=/S/HSM1RUKFBfCfv7zHbinUuQzfTaTUOsplW7lJkuFI=; b=RX3ejb+zuJZOhh YHc6G0xJwhWLB8/85Yd1RpaN6V8vd2IRDbLewPX4bi9IyMQuTePjCaGKe1vKhj6gkT5bv+MKSbhaH Ao/TmfIO0nKwWXhDGqnFRfrOanFrAIPRTY6Zb0fFQcCN8oIiKMylhGv+wAcMvwxrZU5BlvcYxa83X 8zyZl3Zrev+0DvDS8dEHjZSGt+lLslGDp0/6Oj20Fwe+HhzUGkcwFjwMBPdrUzim7DK2rnOEHBMyO yNEYwOeVGxC3kBs3qYtTTMaEKbd451+KaSNKLrdHeJG0uLptMtrqBbVxwI1OJCKWSrPuRhnqLnPe4 HeNoAcHYxX06Z8s8Zpcg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h3JnP-0007ju-O5; Mon, 11 Mar 2019 12:12:43 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h3JnL-0007ix-GR for linux-arm-kernel@lists.infradead.org; Mon, 11 Mar 2019 12:12:41 +0000 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 22B80374; Mon, 11 Mar 2019 05:12:36 -0700 (PDT) Received: from lakrids.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 2E8FE3F703; Mon, 11 Mar 2019 05:12:33 -0700 (PDT) Date: Mon, 11 Mar 2019 12:12:28 +0000 From: Mark Rutland To: Yu Zhao , Anshuman Khandual Subject: Re: [PATCH v3 3/3] arm64: mm: enable per pmd page table lock Message-ID: <20190311121147.GA23361@lakrids.cambridge.arm.com> References: <20190218231319.178224-1-yuzhao@google.com> <20190310011906.254635-1-yuzhao@google.com> <20190310011906.254635-3-yuzhao@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190310011906.254635-3-yuzhao@google.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190311_051239_559503_B9930349 X-CRM114-Status: GOOD ( 26.31 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Ard Biesheuvel , Peter Zijlstra , Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Nick Piggin , Jun Yao , linux-mm@kvack.org, "Aneesh Kumar K . V" , Chintan Pandya , Joel Fernandes , "Kirill A . Shutemov" , Andrew Morton , Laura Abbott , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On Sat, Mar 09, 2019 at 06:19:06PM -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. > > We only do so when pmd is not folded, so we don't mistakenly call > pgtable_pmd_page_ctor() on pud or p4d in pgd_pgtable_alloc(). (We > check shift against PMD_SHIFT, which is same as PUD_SHIFT when pmd > is folded). Just to check, I take it pgtable_pmd_page_ctor() is now a NOP when the PMD is folded, and this last paragraph is stale? > 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 cfbf307d6dc4..a3b1b789f766 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 if PGTABLE_LEVELS > 2 > + > 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); > } > > static inline void pmd_free(struct mm_struct *mm, pmd_t *pmdp) > { > BUG_ON((unsigned long)pmdp & (PAGE_SIZE-1)); > + pgtable_pmd_page_dtor(virt_to_page(pmdp)); > free_page((unsigned long)pmdp); > } It looks like arm64's existing stage-2 code is inconsistent across alloc/free, and IIUC this change might turn that into a real problem. Currently we allocate all levels of stage-2 table with __get_free_page(), but free them with p?d_free(). We always miss the ctor and always use the dtor. Other than that, this patch looks fine to me, but I'd feel more comfortable if we could first fix the stage-2 code to free those stage-2 tables without invoking the dtor. Anshuman, IIRC you had a patch to fix the stage-2 code to not invoke the dtors. If so, could you please post that so that we could take it as a preparatory patch for this series? Thanks, Mark. > diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h > index 106fdc951b6e..4e3becfed387 100644 > --- a/arch/arm64/include/asm/tlb.h > +++ b/arch/arm64/include/asm/tlb.h > @@ -62,7 +62,10 @@ static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, > static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp, > unsigned long addr) > { > - tlb_remove_table(tlb, virt_to_page(pmdp)); > + struct page *page = virt_to_page(pmdp); > + > + pgtable_pmd_page_dtor(page); > + tlb_remove_table(tlb, page); > } > #endif > > -- > 2.21.0.360.g471c308f928-goog > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel