linux-kernel - Re: [PATCH v1 2/4] memblock: update initialization of reserved pages

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Message-ID: <45a7e13d-3e44-3b94-a253-2df72649a83d@redhat.com>
Date:   Tue, 20 Apr 2021 17:18:55 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Anshuman Khandual <anshuman.khandual@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Will Deacon <will@...nel.org>, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v1 2/4] memblock: update initialization of reserved pages

On 20.04.21 17:03, Mike Rapoport wrote:
> On Tue, Apr 20, 2021 at 03:56:28PM +0200, David Hildenbrand wrote:
>> On 20.04.21 11:09, Mike Rapoport wrote:
>>> From: Mike Rapoport <rppt@...ux.ibm.com>
>>>
>>> The struct pages representing a reserved memory region are initialized
>>> using reserve_bootmem_range() function. This function is called for each
>>> reserved region just before the memory is freed from memblock to the buddy
>>> page allocator.
>>>
>>> The struct pages for MEMBLOCK_NOMAP regions are kept with the default
>>> values set by the memory map initialization which makes it necessary to
>>> have a special treatment for such pages in pfn_valid() and
>>> pfn_valid_within().
>>
>> Just a general question while thinking about it:
>>
>> Would we right now initialize the memmap of these pages already via
>> memmap_init_zone()->memmap_init_range()? (IOW, not marking the
>> PageReserved?)
> 
> Yep. These pages are part of memblock.memory so they are initialized in
> memmap_init_zone()->memmap_init_range() to the default values.
> 

So instead of fully initializing them again, we mostly would only have 
to set PageReserved(). Not sure how big that memory usually is -- IOW, 
if we really care about optimizing the double-init.

-- 
Thanks,

David / dhildenb