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[65.49.234.56]) by smtp.gmail.com with ESMTPSA id l28-v6sm18423664pfi.4.2018.07.06.02.27.37 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 06 Jul 2018 02:27:58 -0700 (PDT) Subject: Re: [PATCH v10 0/6] optimize memblock_next_valid_pfn and early_pfn_valid on arm and arm64 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 References: <1530864860-7671-1-git-send-email-hejianet@gmail.com> From: Jia He Message-ID: Date: Fri, 6 Jul 2018 17:27:37 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 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: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sorry for my mistake, I have to resend this set because I missed some important maillists. Please ignore this thread. Terribly sorry about it Cheers， 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