From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: Difference between alloc_domheap_pages vs. alloc_xenheap_pages? Date: Thu, 27 Jun 2013 09:19:58 +0100 Message-ID: References: <1372320702.28443.8.camel@zakaz.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1372320702.28443.8.camel@zakaz.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell , Xinxin Jin Cc: Xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 27/06/2013 09:11, "Ian Campbell" wrote: > On Wed, 2013-06-26 at 15:41 -0700, Xinxin Jin wrote: > > >> I noticed the only difference between the two is to add PGC_xen_heap >> flag in allocated xenheap pages. So does it matter to exchange these >> two functions when allocating a heap page? > > xenheap pages are always mapped, domheap pages are only mapped on demand > with (un)map_domain_page. The big clue is that alloc_xenheap_pages > returns a void* while alloc_domheap_pages returns a struct page_info*. > > On some architectures with a large virtual address space (i.e. 64-bit > ones) the two can be combined and the distinction becomes a bit moot, > but it remains for the benefit of common code and also because even on > 64-bit architectures when you have large amounts of RAM you may still > end up with RAM which is not permanently mapped -- e.g. on x86_64 if you > have >5TB of RAM then you end up with a split again. Also xenheap-allocated pages must be explicitly freed by Xen, usually during domain destruction. > Ian. > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel