linux-kernel - Re: [PATCH v3] arm64/mm: add fallback option to allocate virtually contiguous memory

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Message-ID: <541f79b6b5f3640c1e4978931ae93a38@codeaurora.org>
Date:   Fri, 16 Oct 2020 11:49:02 -0700
From:   Sudarshan Rajagopalan <sudaraja@...eaurora.org>
To:     Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Gavin Shan <gshan@...hat.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Logan Gunthorpe <logang@...tatee.com>,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Price <steven.price@....com>
Subject: Re: [PATCH v3] arm64/mm: add fallback option to allocate virtually
 contiguous memory

On 2020-10-15 01:36, Will Deacon wrote:
> On Wed, Oct 14, 2020 at 05:51:23PM -0700, Sudarshan Rajagopalan wrote:
>> When section mappings are enabled, we allocate vmemmap pages from
>> physically continuous memory of size PMD_SIZE using
>> vmemmap_alloc_block_buf(). Section mappings are good to reduce TLB
>> pressure. But when system is highly fragmented and memory blocks are
>> being hot-added at runtime, its possible that such physically 
>> continuous
>> memory allocations can fail. Rather than failing the memory hot-add
>> procedure, add a fallback option to allocate vmemmap pages from
>> discontinuous pages using vmemmap_populate_basepages().
>> 
>> Signed-off-by: Sudarshan Rajagopalan <sudaraja@...eaurora.org>
>> Reviewed-by: Gavin Shan <gshan@...hat.com>
>> Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Anshuman Khandual <anshuman.khandual@....com>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: Logan Gunthorpe <logang@...tatee.com>
>> Cc: David Hildenbrand <david@...hat.com>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Steven Price <steven.price@....com>
>> ---
>>  arch/arm64/mm/mmu.c | 7 +++++--
>>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> Please can you fix the subject? I have three copies of "PATCH v3" from
> different days in my inbox. I know it sounds trivial, but getting these
> little things right really helps with review, especially when it's 
> sitting
> amongst a sea of other patches.

Yes sure, sorry about that - will change it to "PATCH v4" to make it 
stand out from other patches.

> 
> Thanks,
> 
> Will


Sudarshan

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