Re: [RFC][PATCH] drivers: base: dynamic memory block creation

From: Yinghai Lu <yinghai@kernel.org>
To: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Dave Hansen <dave@sr71.net>,
	Nathan Fontenot <nfont@linux.vnet.ibm.com>,
	Cody P Schafer <cody@linux.vnet.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Lai Jiangshan <laijs@cn.fujitsu.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux MM <linux-mm@kvack.org>
Subject: Re: [RFC][PATCH] drivers: base: dynamic memory block creation
Date: Wed, 14 Aug 2013 16:20:06 -0700	[thread overview]
Message-ID: <CAE9FiQXJ85Nr6F=mn5DgfanwNA2s55=_LyQKbXLrxfTc6yZcAQ@mail.gmail.com> (raw)
In-Reply-To: <20130814215253.GC17423@variantweb.net>

On Wed, Aug 14, 2013 at 2:52 PM, Seth Jennings
<sjenning@linux.vnet.ibm.com> wrote:
> On Wed, Aug 14, 2013 at 02:37:26PM -0700, Yinghai Lu wrote:

> If I am understanding you correctly, you are suggesting we make the block size
> a boot time tunable.  It can't be a runtime tunable since the memory blocks are
> currently created a boot time.

yes.

If could make it to be tunable at run-time, could be much better.

>
> On ppc64, we can't just just choose a memory block size since it must align
> with the underlying LMB (logical memory block) size, set in the hardware ahead
> of time.

assume for x86_64, it now support 46bits physical address. so if we
change to 2G, then
big system will only need create (1<<15) aka 32k entries in /sys at most.

Thanks

Yinghai