From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Christoph Lameter <clameter@sgi.com>, Ingo Molnar <mingo@elte.hu>,
LKML <linux-kernel@vger.kernel.org>,
Rusty Russell <rusty@rustcorp.com.au>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Yasunori Goto <y-goto@jp.fujitsu.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 3 of 4] sparsemem: reduce i386 PAE section size
Date: Fri, 28 Mar 2008 09:43:19 -0700 [thread overview]
Message-ID: <1206722599.7883.119.camel@nimitz.home.sr71.net> (raw)
In-Reply-To: <47EC8DD0.4090401@goop.org>
On Thu, 2008-03-27 at 23:18 -0700, Jeremy Fitzhardinge wrote:
> Christoph Lameter wrote:
> > Only works on i386 if you either use sparsemem / vmemmap or not sparsemem
> > though. Is there any need for the other sparsemem memory models? Or could
> > we disable them like on x86_64?
>
> Probably, but I don't know what the tradeoffs are. All I want is
> hotplug memory.
Developers should probably learn the tradeoffs before they go start
poking around in code and sending patches. ;)
Maybe Christoph has a good idea what the tradeoffs are for the vmemmap
variant, but the table-based one is pretty simple. Smaller sections
mean that it costs you larger sparsemem structures and more bits in
page->flags. But, the smaller the section, the more mem_map[] you might
waste.
BTW, the current 1G sections were picked because all the hardware we
knew of at the time had 512MB dimms that had to be added in pairs. So,
we didn't ever have physical hotplug of less than that.
-- Dave
next prev parent reply other threads:[~2008-03-28 16:43 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-28 0:28 [PATCH 0 of 4] [RFC] hotplug memory: minor updates Jeremy Fitzhardinge
2008-03-28 0:28 ` [PATCH 1 of 4] hotplug-memory: add add_memory_resource Jeremy Fitzhardinge
2008-03-28 0:28 ` [PATCH 2 of 4] hotplug-memory: adding non-section-aligned memory is bad Jeremy Fitzhardinge
2008-03-28 1:27 ` KAMEZAWA Hiroyuki
2008-03-28 1:34 ` Yasunori Goto
2008-03-28 1:54 ` KAMEZAWA Hiroyuki
2008-03-28 2:13 ` Jeremy Fitzhardinge
2008-03-28 2:33 ` KAMEZAWA Hiroyuki
2008-03-28 2:51 ` Jeremy Fitzhardinge
2008-03-28 3:17 ` KAMEZAWA Hiroyuki
2008-03-28 4:20 ` Jeremy Fitzhardinge
2008-03-28 4:39 ` KAMEZAWA Hiroyuki
2008-03-28 18:19 ` Jeremy Fitzhardinge
2008-03-28 18:27 ` Dave Hansen
2008-03-28 3:21 ` Yasunori Goto
2008-03-28 4:07 ` Jeremy Fitzhardinge
2008-03-28 21:30 ` Jeremy Fitzhardinge
2008-03-28 0:28 ` [PATCH 3 of 4] sparsemem: reduce i386 PAE section size Jeremy Fitzhardinge
2008-03-28 0:35 ` Christoph Lameter
2008-03-28 2:26 ` Jeremy Fitzhardinge
2008-03-28 2:27 ` Christoph Lameter
2008-03-28 6:18 ` Jeremy Fitzhardinge
2008-03-28 16:43 ` Dave Hansen [this message]
2008-03-28 18:05 ` Jeremy Fitzhardinge
2008-03-28 16:45 ` Dave Hansen
2008-03-28 0:28 ` [PATCH 4 of 4] paravirt_ops: don't steal memory resources in paravirt_disable_iospace Jeremy Fitzhardinge
2008-03-28 2:41 ` Rusty Russell
2008-03-28 9:12 ` [PATCH 0 of 4] [RFC] hotplug memory: minor updates Ingo Molnar
2008-03-28 16:07 ` Jeremy Fitzhardinge
2008-03-28 22:04 ` Ingo Molnar
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