From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx203.postini.com [74.125.245.203]) by kanga.kvack.org (Postfix) with SMTP id 2E69E6B005A for ; Tue, 30 Oct 2012 05:12:28 -0400 (EDT) Subject: Re: [PATCH 0/3] KVM: PPC: Book3S HV: More flexible allocator for linear memory Mime-Version: 1.0 (Apple Message framework v1278) Content-Type: text/plain; charset=us-ascii From: Alexander Graf In-Reply-To: <20121026011733.GA31394@drongo> Date: Tue, 30 Oct 2012 10:12:19 +0100 Content-Transfer-Encoding: quoted-printable Message-Id: <807B8637-B694-42A3-B615-97AC5E24B26E@suse.de> References: <20120912003427.GH32642@bloggs.ozlabs.ibm.com> <9650229C-2512-4684-98EC-6E252E47C4A9@suse.de> <20120914081140.GC15028@bloggs.ozlabs.ibm.com> <20120914124504.GF15028@bloggs.ozlabs.ibm.com> <20121026011733.GA31394@drongo> Sender: owner-linux-mm@kvack.org List-ID: To: Paul Mackerras Cc: kvm-ppc@vger.kernel.org, KVM list , linux-mm@kvack.org, mina86@mina86.com On 26.10.2012, at 03:17, Paul Mackerras wrote: > On Fri, Sep 14, 2012 at 03:15:32PM +0200, Alexander Graf wrote: >>=20 >> On 14.09.2012, at 14:45, Paul Mackerras wrote: >>=20 >>> On Fri, Sep 14, 2012 at 02:13:37PM +0200, Alexander Graf wrote: >>>=20 >>>> So do you think it makes more sense to reimplement a large page = allocator in KVM, as this patch set does, or improve CMA to get us = really big chunks of linear memory? >>>>=20 >>>> Let's ask the Linux mm guys too :). Maybe they have an idea. >>>=20 >>> I asked the authors of CMA, and apparently it's not limited to >>> MAX_ORDER as I feared. It has the advantage that the memory can be >>> used for other things such as page cache when it's not needed, but = not >>> for immovable allocations such as kmalloc. I'm going to try it out. >>> It will need a patch to increase the maximum alignment it allows. >>=20 >> Awesome. Thanks a lot. I'd really prefer if we can stick to generic = Linux solutions rather than invent our own :). >=20 > Turns out there is a difficulty with this. When we have a guest page > that we want to pin in memory, and that page happens to have been > allocated within the CMA region, we would need to migrate it out of > the CMA region before pinning it, since otherwise it would reduce the > amount of contiguous memory available. But it appears that there > isn't any way to do that. How does this work for other users of CMA? I can't possibly believe that = we only ever want a static amount of contiguous memory on the system. Alex -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org