From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 03FBC6B026F for ; Fri, 6 Jul 2018 05:28:01 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id t78-v6so6721774pfa.8 for ; Fri, 06 Jul 2018 02:28:00 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id f7-v6sor2433445plo.52.2018.07.06.02.27.59 for (Google Transport Security); Fri, 06 Jul 2018 02:27:59 -0700 (PDT) Subject: Re: [PATCH v10 0/6] optimize memblock_next_valid_pfn and early_pfn_valid on arm and arm64 References: <1530864860-7671-1-git-send-email-hejianet@gmail.com> From: Jia He Message-ID: Date: Fri, 6 Jul 2018 17:27:37 +0800 MIME-Version: 1.0 In-Reply-To: <1530864860-7671-1-git-send-email-hejianet@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Jia He , Russell King , Andrew Morton , Michal Hocko , Catalin Marinas , Mel Gorman , Will Deacon , Mark Rutland , "H. Peter Anvin" Cc: Pavel Tatashin , Daniel Jordan , AKASHI Takahiro , Gioh Kim , Steven Sistare , Daniel Vacek , Eugeniu Rosca , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org, James Morse , Ard Biesheuvel , Steve Capper , Thomas Gleixner , Ingo Molnar , Greg Kroah-Hartman , Kate Stewart , Philippe Ombredanne , Johannes Weiner , Kemi Wang , Petr Tesarik , YASUAKI ISHIMATSU , Andrey Ryabinin , Nikolay Borisov , richard.weiyang@gmail.com, Jia He Sorry for my mistake, I have to resend this set because I missed some important maillists. Please ignore this thread. Terribly sorry about it Cheersi 1/4 ? Jia On 7/6/2018 4:14 PM, Jia He Wrote: > From: Jia He > > 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 > > Patch 1 introduces new config to make codes more generic > Patch 2 remains the memblock_next_valid_pfn on arm and arm64,this patch is > originated from b92df1de5 > Patch 3 optimizes the memblock_next_valid_pfn() > Patch 4~6 optimizes the early_pfn_valid() > > Changelog: > V10:- move codes to memblock.c, refine the performance consideration > V9: - rebase to mmotm master, refine the log description. No major changes > V8: - introduce new config and move generic code to early_pfn.h > - optimize memblock_next_valid_pfn as suggested by Matthew Wilcox > V7: - fix i386 compilation error. refine the commit description > V6: - simplify the codes, move arm/arm64 common codes to one file. > - refine patches as suggested by Danial Vacek and Ard Biesheuvel > V5: - further refining as suggested by Danial Vacek. Make codes > arm/arm64 more arch specific > V4: - refine patches as suggested by Danial Vacek and Wei Yang > - optimized on arm besides arm64 > V3: - fix 2 issues reported by kbuild test robot > V2: - rebase to mmotm latest > - remain memblock_next_valid_pfn on arm64 > - refine memblock_search_pfn_regions and pfn_valid_region > > Jia He (6): > arm: arm64: introduce CONFIG_HAVE_MEMBLOCK_PFN_VALID > mm: page_alloc: remain memblock_next_valid_pfn() on arm/arm64 > mm: page_alloc: reduce unnecessary binary search in > memblock_next_valid_pfn() > mm/memblock: introduce memblock_search_pfn_regions() > mm/memblock: introduce pfn_valid_region() > mm: page_alloc: reduce unnecessary binary search in early_pfn_valid() > > arch/arm/Kconfig | 4 +++ > arch/arm64/Kconfig | 4 +++ > include/linux/memblock.h | 2 ++ > include/linux/mmzone.h | 16 +++++++++ > mm/Kconfig | 3 ++ > mm/memblock.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++ > mm/page_alloc.c | 5 ++- > 7 files changed, 117 insertions(+), 1 deletion(-) > -- Cheers, Jia