Re: [PATCH v2 2/4] mm: make the threshold of enabling THP configurable

From: Cong Wang <amwang@redhat.com>
To: David Rientjes <rientjes@google.com>
Cc: linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	dave@linux.vnet.ibm.com, Andrea Arcangeli <aarcange@redhat.com>,
	Mel Gorman <mel@csn.ul.ie>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Rik van Riel <riel@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
	linux-mm@kvack.org
Subject: Re: [PATCH v2 2/4] mm: make the threshold of enabling THP configurable
Date: Wed, 22 Jun 2011 11:06:30 +0800	[thread overview]
Message-ID: <4E015C36.2050005@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1106211817340.5205@chino.kir.corp.google.com>

于 2011年06月22日 09:23, David Rientjes 写道:
> On Tue, 21 Jun 2011, Amerigo Wang wrote:
>
>> Don't hard-code 512M as the threshold in kernel, make it configruable,
>> and set 512M by default.
>>
>> And print info when THP is disabled automatically on small systems.
>>
>> V2: Add more description in help messages, correct some typos,
>> print the mini threshold too.
>>
>
> I like the printk that notifies users why THP was disabled because it
> could potentially be a source of confusion (and fixing the existing typos
> in hugepage_init() would also be good).  However, I disagree that we need
> to have this as a config option: you either want the feature for your
> systems or you don't.  Perhaps add a "transparent_hugepage=force" option
> that will act as "always" but also force it to be enabled in all
> scenarios, even without X86_FEATURE_PSE, that will override all the logic
> that thinks it knows better?

I think that is overkill, because we can still enable THP via /sys
for small systems.

Thanks.