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

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Message-ID: <20180720210626.5bnyddmn4avp2l3x@kshutemo-mobl1>
Date:   Sat, 21 Jul 2018 00:06:26 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
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 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.

-- 
 Kirill A. Shutemov