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Subject: Re: [RESEND PATCH v10 6/6] mm: page_alloc: reduce unnecessary binary
 search in early_pfn_valid()
To:     Pasha Tatashin <Pavel.Tatashin@microsoft.com>,
        Jia He <hejianet@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>
Cc:     Wei Yang <richard.weiyang@gmail.com>,
        Kees Cook <keescook@chromium.org>,
        Laura Abbott <labbott@redhat.com>,
        Vladimir Murzin <vladimir.murzin@arm.com>,
        Philip Derrin <philip@cog.systems>,
        AKASHI Takahiro <takahiro.akashi@linaro.org>,
        James Morse <james.morse@arm.com>,
        Steve Capper <steve.capper@arm.com>,
        pavel.tatashin@microsoft.com,
        Gioh Kim <gi-oh.kim@profitbricks.com>,
        Vlastimil Babka <vbabka@suse.cz>, Mel Gorman <mgorman@suse.de>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Kemi Wang <kemi.wang@intel.com>,
        Petr Tesarik <ptesarik@suse.com>,
        YASUAKI ISHIMATSU <yasu.isimatu@gmail.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Nikolay Borisov <nborisov@suse.com>,
        Daniel Jordan <daniel.m.jordan@oracle.com>,
        Daniel Vacek <neelx@redhat.com>,
        Eugeniu Rosca <erosca@de.adit-jv.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Jia He <jia.he@hxt-semitech.com>
References: <1530867675-9018-1-git-send-email-hejianet@gmail.com>
 <1530867675-9018-7-git-send-email-hejianet@gmail.com>
 <c6ed43ee-b09e-1f75-43b3-6cd2808d13f3@microsoft.com>
From:   Pavel Tatashin <pasha.tatashin@gmail.com>
Message-ID: <831be9a1-6401-3af0-b68b-b3e25db806f9@gmail.com>
Date:   Thu, 16 Aug 2018 21:38:15 -0400
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On 8/16/18 9:35 PM, Pasha Tatashin wrote:
> 
> 
> On 7/6/18 5:01 AM, Jia He wrote:
>> Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
>> where possible") optimized the loop in memmap_init_zone(). But there is
>> still some room for improvement. E.g. in early_pfn_valid(), if pfn and
>> pfn+1 are in the same memblock region, we can record the last returned
>> memblock region index and check whether pfn++ is still in the same
>> region.
>>
>> Currently it only improve the performance on arm/arm64 and will have no
>> impact on other arches.
>>
>> For the performance 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).
> 
> This series would be a lot simpler if patches 4, 5, and 6 were dropped.
> The extra complexity does not make sense to save 0.0001s/T during not.
s/not/boot

> 
> Patches 1-3, look OK, but without patches 4-5 __init_memblock should be
> made local static as I suggested earlier.
s/__init_memblock/early_region_idx