linux-kernel - Re: [PATCH] mm: thp: remove use_zero

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Date:   Fri, 20 Jul 2018 16:51:31 -0700
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     hughd@...gle.com, rientjes@...gle.com, aaron.lu@...el.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: thp: remove use_zero_page sysfs knob



On 7/20/18 2:06 PM, Kirill A. Shutemov wrote:
> On Sat, Jul 21, 2018 at 02:13:50AM +0800, Yang Shi wrote:
>> By digging into the original review, it looks use_zero_page sysfs knob
>> was added to help ease-of-testing and give user a way to mitigate
>> refcounting overhead.
>>
>> It has been a few years since the knob was added at the first place, I
>> think we are confident that it is stable enough. And, since commit
>> 6fcb52a56ff60 ("thp: reduce usage of huge zero page's atomic counter"),
>> it looks refcounting overhead has been reduced significantly.
>>
>> Other than the above, the value of the knob is always 1 (enabled by
>> default), I'm supposed very few people turn it off by default.
>>
>> So, it sounds not worth to still keep this knob around.
> I don't think that having the knob around is huge maintenance burden.
> And since it helped to workaround a security bug relative recently I would
> rather keep it.

I agree to keep it for a while to let that security bug cool down, 
however, if there is no user anymore, it sounds pointless to still keep 
a dead knob.

>