From: Geoff Levand <geoffrey.levand@am•sony.com>
To: benh@kernel•crashing.org
Cc: linuxppc-dev list <linuxppc-dev@ozlabs•org>
Subject: Re: [RFC] [PATCH] vmemmap fixes to use smaller pages
Date: Thu, 1 May 2008 14:46:56 -0700 [thread overview]
Message-ID: <481A3A50.3060101@am.sony.com> (raw)
In-Reply-To: <1209534108.18023.221.camel@pasglop>
Benjamin Herrenschmidt wrote:
> This patch changes vmemmap to use a different region (region 0xf) of the
> address space whose page size can be dynamically configured at boot.
>
> The problem with the current approach of always using 16M pages is that
> it's not well suited to machines that have small amounts of memory such
> as small partitions on pseries, or PS3's.
>
> In fact, on the PS3, failure to allocate the 16M page backing vmmemmap
> tends to prevent hotplugging the HV's "additional" memory, thus limiting
> the available memory even more, from my experience down to something
> like 80M total, which makes it really not very useable.
>
> The logic used by my match to choose the vmemmap page size is:
>
> - If 16M pages are available and there's 1G or more RAM at boot, use that size.
> - Else if 64K pages are available, use that
> - Else use 4K pages
It doesn't seem to cause problems on PS3, and I added it into ps3-linux.git
as other/powerpc-vmemmap-variable-page-size.diff, but I couldn't get it to
fail without the patch...
Could you send me your kernel .config?
-Geoff
next prev parent reply other threads:[~2008-05-01 21:47 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-30 5:41 [RFC] [PATCH] vmemmap fixes to use smaller pages Benjamin Herrenschmidt
2008-04-30 19:06 ` Geoff Levand
2008-04-30 21:18 ` Benjamin Herrenschmidt
2008-05-01 21:46 ` Geoff Levand [this message]
2008-05-01 22:39 ` Benjamin Herrenschmidt
2008-05-02 22:21 ` Geoff Levand
2008-05-15 20:07 ` Geoff Levand
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