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From: Mathieu Desnoyers <compudj@krystal.dyndns.org>
To: Dave Hansen <haveblue@us.ibm.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, mbligh@google.com
Subject: Re: [RFC 5/7] LTTng instrumentation mm
Date: Mon, 19 Nov 2007 14:00:40 -0500	[thread overview]
Message-ID: <20071119190040.GA1609@Krystal> (raw)
In-Reply-To: <20071119185258.GA998@Krystal>

* 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

  reply	other threads:[~2007-11-19 19:00 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-11-13 19:33 [RFC 0/7] LTTng Kernel Instrumentation (Architecture Independent) Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 1/7] Include marker.h in kernel.h -- temporary, for code readability Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 2/7] LTTng instrumentation fs Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 3/7] LTTng instrumentation ipc Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 4/7] LTTng instrumentation kernel Mathieu Desnoyers
2007-11-15 23:30   ` Mike Mason
2007-11-15 23:54     ` Mike Mason
2007-11-16  2:42       ` Mathieu Desnoyers
2007-11-16  2:22     ` Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 5/7] LTTng instrumentation mm Mathieu Desnoyers
2007-11-15 21:06   ` Dave Hansen
2007-11-15 21:51     ` Mathieu Desnoyers
2007-11-15 22:16       ` Dave Hansen
2007-11-16 14:30         ` Mathieu Desnoyers
2007-11-19 18:04           ` Dave Hansen
2007-11-28 14:09             ` [RFC PATCH] LTTng instrumentation mm (using page_to_pfn) Mathieu Desnoyers
2007-11-28 16:54               ` Dave Hansen
2007-11-29  2:34                 ` Mathieu Desnoyers
2007-11-29  6:25                   ` Dave Hansen
2007-11-30 16:11                     ` [RFC PATCH] LTTng instrumentation mm (updated) Mathieu Desnoyers
2007-11-30 17:46                       ` Dave Hansen
2007-11-30 17:05                         ` Mathieu Desnoyers
2007-11-30 18:42                           ` Dave Hansen
2007-11-30 19:10                             ` Mathieu Desnoyers
2007-12-04 19:15                               ` Frank Ch. Eigler
2007-12-04 19:25                                 ` Mathieu Desnoyers
2007-12-04 19:40                                   ` Dave Hansen
2007-12-04 20:05                                     ` Mathieu Desnoyers
2007-12-04 20:24                                       ` Dave Hansen
2007-12-04 20:28                                       ` Dave Hansen
2007-11-16 14:47         ` [RFC 5/7] LTTng instrumentation mm Mathieu Desnoyers
2007-11-19 18:07           ` Dave Hansen
2007-11-19 18:52             ` Mathieu Desnoyers
2007-11-19 19:00               ` Mathieu Desnoyers [this message]
2007-11-19 19:43                 ` Dave Hansen
2007-11-19 19:43               ` Dave Hansen
2007-11-19 19:52                 ` [PATCH] Cast __page_to_pfn to unsigned long in CONFIG_SPARSEMEM Mathieu Desnoyers
2007-11-19 20:09                   ` Dave Hansen
2007-11-19 20:20                     ` [PATCH] Cast page_to_pfn " Mathieu Desnoyers
2007-11-19 21:08                       ` Andrew Morton
2007-11-19 21:19                         ` Dave Hansen
2007-11-19 21:26                           ` Dave Hansen
2007-11-21 20:12                           ` Christoph Lameter
2007-11-20 17:34                         ` Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 6/7] LTTng instrumentation net Mathieu Desnoyers
2007-11-13 19:33 ` [RFC 7/7] Add Markers Into Semaphore Primitives Mathieu Desnoyers

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