From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from outbound3-wa4-R.bigfish.com (outbound-wa4.frontbridge.com [216.32.181.16]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "*.bigfish.com", Issuer "*.bigfish.com" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 1E46FDDD0B for ; Fri, 2 May 2008 07:47:24 +1000 (EST) Message-ID: <481A3A50.3060101@am.sony.com> Date: Thu, 1 May 2008 14:46:56 -0700 From: Geoff Levand MIME-Version: 1.0 To: benh@kernel.crashing.org Subject: Re: [RFC] [PATCH] vmemmap fixes to use smaller pages References: <1209534108.18023.221.camel@pasglop> In-Reply-To: <1209534108.18023.221.camel@pasglop> Content-Type: text/plain; charset="UTF-8" Cc: linuxppc-dev list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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