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Subject: Re: [PATCH] mm: thp: remove use_zero_page sysfs knob
To:     "Kirill A. Shutemov" <kirill@shutemov.name>
Cc:     hughd@google.com, rientjes@google.com, aaron.lu@intel.com,
        akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <1532110430-115278-1-git-send-email-yang.shi@linux.alibaba.com>
 <20180720210626.5bnyddmn4avp2l3x@kshutemo-mobl1>
From:   Yang Shi <yang.shi@linux.alibaba.com>
Message-ID: <3118b646-681e-a2aa-dc7b-71d4821fa50f@linux.alibaba.com>
Date:   Fri, 20 Jul 2018 16:51:31 -0700
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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.

>