Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932107Ab2BHQmY (ORCPT ); Wed, 8 Feb 2012 11:42:24 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:45610 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755661Ab2BHQmW (ORCPT ); Wed, 8 Feb 2012 11:42:22 -0500 Message-ID: <4F32A55E.8010401@linux.vnet.ibm.com> Date: Wed, 08 Feb 2012 08:39:58 -0800 From: Dave Hansen User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.24) Gecko/20111109 Lightning/1.0b2 Thunderbird/3.1.16 MIME-Version: 1.0 To: Seth Jennings CC: Greg Kroah-Hartman , Nitin Gupta , Dan Magenheimer , Brian King , Konrad Wilk , linux-mm@kvack.org, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/5] staging: zsmalloc: zsmalloc memory allocation library References: <1326149520-31720-1-git-send-email-sjenning@linux.vnet.ibm.com> <1326149520-31720-2-git-send-email-sjenning@linux.vnet.ibm.com> <4F21A5AF.6010605@linux.vnet.ibm.com> <4F300D41.5050105@linux.vnet.ibm.com> In-Reply-To: <4F300D41.5050105@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12020816-7282-0000-0000-00000653D252 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1305 Lines: 29 On 02/06/2012 09:26 AM, Seth Jennings wrote: > On 01/26/2012 01:12 PM, Dave Hansen wrote: >> void *kmap_atomic_prot(struct page *page, pgprot_t prot) >> { >> ... >> type = kmap_atomic_idx_push(); >> idx = type + KM_TYPE_NR*smp_processor_id(); >> vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx); >> >> I think if you do a get_cpu()/put_cpu() or just a preempt_disable() >> across the operations you'll be guaranteed to get two contiguous addresses. > > I'm not quite following here. kmap_atomic() only does this for highmem pages. > For normal pages (all pages for 64-bit), it doesn't do any mapping at all. It > just returns the virtual address of the page since it is in the kernel's address > space. > > For this design, the pages _must_ be mapped, even if the pages are directly > reachable in the address space, because they must be virtually contiguous. I guess you could use vmap() for that. It's just going to be slower than kmap_atomic(). I'm really not sure it's worth all the trouble to avoid order-1 allocations, though. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/