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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 A7F5AC43334 for ; Thu, 6 Sep 2018 10:46:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C158206BA for ; Thu, 6 Sep 2018 10:46:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6C158206BA 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-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727637AbeIFPVp (ORCPT ); Thu, 6 Sep 2018 11:21:45 -0400 Received: from foss.arm.com ([217.140.101.70]:43048 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725918AbeIFPVo (ORCPT ); Thu, 6 Sep 2018 11:21:44 -0400 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 2E7147A9; Thu, 6 Sep 2018 03:46:53 -0700 (PDT) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id F26C03F557; Thu, 6 Sep 2018 03:46:52 -0700 (PDT) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id B2DD21AE358D; Thu, 6 Sep 2018 11:47:07 +0100 (BST) Date: Thu, 6 Sep 2018 11:47:07 +0100 From: Will Deacon To: Andrew Morton Cc: Jia He , Russell King , Catalin Marinas , Mark Rutland , Ard Biesheuvel , Michal Hocko , Wei Yang , Kees Cook , Laura Abbott , Vladimir Murzin , Philip Derrin , AKASHI Takahiro , James Morse , Steve Capper , Gioh Kim , Vlastimil Babka , Mel Gorman , Johannes Weiner , Kemi Wang , Petr Tesarik , YASUAKI ISHIMATSU , Andrey Ryabinin , Nikolay Borisov , Daniel Jordan , Daniel Vacek , Eugeniu Rosca , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jia He Subject: Re: [PATCH v11 0/3] remain and optimize memblock_next_valid_pfn on arm and arm64 Message-ID: <20180906104707.GL3592@arm.com> References: <1534907237-2982-1-git-send-email-jia.he@hxt-semitech.com> <20180905145755.cc89819d446f311e4b8e8f95@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180905145755.cc89819d446f311e4b8e8f95@linux-foundation.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 05, 2018 at 02:57:55PM -0700, Andrew Morton wrote: > On Wed, 22 Aug 2018 11:07:14 +0800 Jia He wrote: > > > Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns > > where possible") optimized the loop in memmap_init_zone(). But it causes > > possible panic bug. So Daniel Vacek reverted it later. > > > > But as suggested by Daniel Vacek, it is fine to using memblock to skip > > gaps and finding next valid frame with CONFIG_HAVE_ARCH_PFN_VALID. > > > > More from what Daniel said: > > "On arm and arm64, memblock is used by default. But generic version of > > pfn_valid() is based on mem sections and memblock_next_valid_pfn() does > > not always return the next valid one but skips more resulting in some > > valid frames to be skipped (as if they were invalid). And that's why > > kernel was eventually crashing on some !arm machines." > > > > About the performance consideration: > > As said by James in b92df1de5, > > "I have tested this patch on a virtual model of a Samurai CPU with a > > sparse memory map. The kernel boot time drops from 109 to 62 seconds." > > Thus it would be better if we remain memblock_next_valid_pfn on arm/arm64. > > > > Besides we can remain memblock_next_valid_pfn, there is still some room > > for improvement. After this set, I can see the time overhead of memmap_init > > is reduced from 27956us to 13537us in my armv8a server(QDF2400 with 96G > > memory, pagesize 64k). I believe arm server will benefit more if memory is > > larger than TBs > > Thanks. I switched to v11. It would be nice to see some confirmation > from ARM people please? I'll take a look... Will