From: Dave Hansen <haveblue@us.ibm.com>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
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 10:07:05 -0800 [thread overview]
Message-ID: <1195495626.27759.119.camel@localhost> (raw)
In-Reply-To: <20071116144742.GA17255@Krystal>
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'
-- Dave
next prev parent reply other threads:[~2007-11-19 18:07 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 [this message]
2007-11-19 18:52 ` Mathieu Desnoyers
2007-11-19 19:00 ` Mathieu Desnoyers
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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