linux-kernel - Re: [PATCH] mm/huge_memory: disable thp if thp page size is too large

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Message-ID: <6813b6fa-5587-7967-1f16-87b1c49084a1@redhat.com>
Date:   Wed, 6 Oct 2021 10:20:20 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Hao Peng <flyingpenghao@...il.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/huge_memory: disable thp if thp page size is too large

On 06.10.21 10:16, Hao Peng wrote:
> On Thu, Sep 30, 2021 at 9:19 PM David Hildenbrand <david@...hat.com> wrote:
>>
>> On 30.09.21 04:14, Hao Peng wrote:
>>> From: Peng Hao <flyingpeng@...cent.com>
>>
>> "disable thp if thp page size is too large" you disable thp if there is
>> not sufficient memory installed in the system (and for that, you use THP
>> size), something doesn't add up here.
>>
> In addition, if THP is enabled, min_free_kbytes will be recalculated.
> At this time,
> min_free_kbytes is calculated based on the size of THP. If the size of
> THP is too l
> arge, OOM will easily be triggered.

Right, I was pointing at the misleading $subject. What about something like:

"mm/huge_memory: disable THP with large THP size on small present memory" ?

>>>
>>> After seting the page size to 64k on ARM64, the supported huge page
>>
>> s/seting/setting/
>>
>> Fortunately, most distributions already switched to 4k, because 512MB
>> THP is pretty much useless, especially on any system that doesn't have
>> memory in the range of hundreds of megabytes or terrabytes.
> But the ARM64 Server distribution version I use, such as CentOS for ARM64,
>   has a page size of 16KB or 64KB.

Yeah, RHEL8 and CENTOS8 are the last remaining "recent distirbutions" 
I'm aware of.


-- 
Thanks,

David / dhildenb