Re: [PATCH 2/3] mm: make the threshold of enabling THP configurable

[Cong Wang]

ä 2011å06æ22æ 19:15, Mel Gorman åé:
> On Wed, Jun 22, 2011 at 06:46:39PM +0800, Cong Wang wrote:
> > ??? 2011???06???22??? 17:16, Mel Gorman ??????:
> > > What I meant was that there is a rational reason why 512M is the
> > > default for enabling THP by default. Tuning it lower than that by any
> > > means makes very little sense. Tuning it higher might make some sense
> > > but it is more likely that THP would simply be disabled via sysctl. I
> > > see very little advantage to introducing this Kconfig option other
> > > than as a source of confusion when running make oldconfig.
> >
> > The tunable range is (512, 8192), so 512M is the minimum.
> >
> > Sure, I knew it can be disabled via /sys, actually we can do even
> > more in user-space, that is totally move the 512M check out of kernel,
> > why we didn't?
>
> Because the reason why 512M is the default is not obvious and there
> was no guarantee all distros would chose a reasonable default for
> an init script (or know that an init script was even necessary).
> This is one of the few cases where there is a sensible default that
> is the least surprising.

Putting a well-explained Kconfig help would solve this problem,
so I don't think this is a surprising thing.
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