Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH] mm/huge_memory: disable thp if thp page size is too large
To:     Hao Peng <flyingpenghao@gmail.com>
Cc:     akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <CAPm50aLBfe7N_udxCkS3-PKbTmUvSpqu0sL7U6qHXZ=OWGQnTQ@mail.gmail.com>
 <914a0b38-cb44-f4be-43aa-bc42bee1553b@redhat.com>
 <CAPm50aKRTg2=WMDw+vWvXA5+wADfSo8Kk-PHpAagftGypArU+g@mail.gmail.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
Message-ID: <6813b6fa-5587-7967-1f16-87b1c49084a1@redhat.com>
Date:   Wed, 6 Oct 2021 10:20:20 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.11.0
MIME-Version: 1.0
In-Reply-To: <CAPm50aKRTg2=WMDw+vWvXA5+wADfSo8Kk-PHpAagftGypArU+g@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 06.10.21 10:16, Hao Peng wrote:
> On Thu, Sep 30, 2021 at 9:19 PM David Hildenbrand <david@redhat.com> wrote:
>>
>> On 30.09.21 04:14, Hao Peng wrote:
>>> From: Peng Hao <flyingpeng@tencent.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