From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from toip6.srvr.bell.ca ([209.226.175.125]) by tomts22-srv.bellnexxia.net (InterMail vM.5.01.06.13 201-253-122-130-113-20050324) with ESMTP id <20071119190548.SSMT18413.tomts22-srv.bellnexxia.net@toip6.srvr.bell.ca> for ; Mon, 19 Nov 2007 14:05:48 -0500 Date: Mon, 19 Nov 2007 14:00:40 -0500 From: Mathieu Desnoyers Subject: Re: [RFC 5/7] LTTng instrumentation mm Message-ID: <20071119190040.GA1609@Krystal> References: <20071113193349.214098508@polymtl.ca> <20071113194025.150641834@polymtl.ca> <1195160783.7078.203.camel@localhost> <20071115215142.GA7825@Krystal> <1195164977.27759.10.camel@localhost> <20071116144742.GA17255@Krystal> <1195495626.27759.119.camel@localhost> <20071119185258.GA998@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20071119185258.GA998@Krystal> Sender: owner-linux-mm@kvack.org Return-Path: To: Dave Hansen Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mbligh@google.com List-ID: * Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca) wrote: > * Dave Hansen (haveblue@us.ibm.com) wrote: > > On Fri, 2007-11-16 at 09:47 -0500, Mathieu Desnoyers wrote: > > > * Dave Hansen (haveblue@us.ibm.com) wrote: > > > > For most (all?) architectures, the PFN and the virtual address in the > > > > kernel's linear are interchangeable with pretty trivial arithmetic. All > > > > pages have a pfn, but not all have a virtual address. Thus, I suggested > > > > using the pfn. What kind of virtual addresses are you talking about? > > > > > > > > > > Hrm, in asm-generic/memory_model.h, we have various versions of > > > __page_to_pfn. Normally they all cast the result to (unsigned long), > > > except for : > > > > > > > > > #elif defined(CONFIG_SPARSEMEM_VMEMMAP) > > > > > > /* memmap is virtually contigious. */ > > > #define __pfn_to_page(pfn) (vmemmap + (pfn)) > > > #define __page_to_pfn(page) ((page) - vmemmap) > > > > > > So I guess the result is a pointer ? Should this be expected ? > > > > Nope. 'pointer - pointer' is an integer. Just solve this equation for > > integer: > > > > 'pointer + integer = pointer' > > > > Well, using page_to_pfn turns out to be ugly in markers (and in > printks) then. Depending on the architecture, it will result in either > an unsigned long (x86_64) or an unsigned int (i386), which corresponds Well, it's signed long and signed int, but the point is still valid. > to %lu or %u and will print a warning if we don't cast it explicitly. > > Mathieu > > > > -- Dave > > > > -- > Mathieu Desnoyers > Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- 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