linux-kernel - Re: [PATCH v12 2/2] mm: page_alloc: reduce unnecessary binary search in memblock_next_valid

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Message-ID: <868f90c7-a728-9eb3-7529-f5a8a501a76a@huawei.com>
Date:   Wed, 24 Jul 2019 16:33:01 +0800
From:   Hanjun Guo <guohanjun@...wei.com>
To:     Mike Rapoport <rppt@...ux.ibm.com>
CC:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        Jia He <hejianet@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v12 2/2] mm: page_alloc: reduce unnecessary binary search
 in memblock_next_valid_pfn

On 2019/7/23 16:33, Mike Rapoport wrote:
> On Tue, Jul 23, 2019 at 01:51:13PM +0800, Hanjun Guo wrote:
>> From: Jia He <hejianet@...il.com>
>>
>> After skipping some invalid pfns in memmap_init_zone(), there is still
>> some room for improvement.
>>
>> E.g. if pfn and pfn+1 are in the same memblock region, we can simply pfn++
>> instead of doing the binary search in memblock_next_valid_pfn.
>>
>> Furthermore, if the pfn is in a gap of two memory region, skip to next
>> region directly to speedup the binary search.
> How much speed up do you see with this improvements relatively to simple
> binary search in memblock_next_valid_pfn()?

The major speedup on my platform is the previous patch in this patch set,
not this one, I think it's related to sparse memory mode for different
platforms.

Thanks
Hanjun

>