linux-kernel - Re: [LKML] Re: USB transfer_buffer allocations on 64bit systems

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Message-ID: <q2r74fd948d1004120506i302c1238jf68ae0290f60bd6c@mail.gmail.com>
Date:	Mon, 12 Apr 2010 13:06:51 +0100
From:	Pedro Ribeiro <pedrib@...il.com>
To:	Daniel Mack <daniel@...aq.de>
Cc:	Robert Hancock <hancockrwd@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Greg KH <gregkh@...e.de>, alsa-devel@...a-project.org,
	linux-usb@...r.kernel.org
Subject: Re: [LKML] Re: USB transfer_buffer allocations on 64bit systems

On 12 April 2010 11:48, Daniel Mack <daniel@...aq.de> wrote:
> On Fri, Apr 09, 2010 at 04:11:52PM -0600, Robert Hancock wrote:
>> On Fri, Apr 9, 2010 at 3:23 PM, Alan Stern <stern@...land.harvard.edu> wrote:
>> > On Fri, 9 Apr 2010, Konrad Rzeszutek Wilk wrote:
>> >
>> >> On Fri, Apr 09, 2010 at 03:34:06PM -0400, Alan Stern wrote:
>> >> > On Fri, 9 Apr 2010, Pedro Ribeiro wrote:
>> >> >
>> >> > > > The DMA pointers do indeed look sane. I wanted to take a deeper look at
>> >> > > > this and set up a 64bit system today. However, I fail to see the problem
>> >> > > > here. Pedro, how much RAM does your machine have installed?
>> >> >
>> >> > > It has 4 GB.
>> >> >
>> >> > That means DMA mapping cannot be the cause of the problem.  :-(
>> >>
>> >> That isn't entirely true. The BIOS usually allocates a 256 MB ACPI/PCI hole
>> >> that is under the 4GB.
>> >>
>> >> So end up with 3.7 GB, then the 256MB hole, and then right above the 4GB
>> >> you the the remaining memory: 4.3GB.
>> >
>> > How can Pedro find out what physical addresses are in use on his
>> > system?
>>
>> If you have 4GB of RAM then almost certainly you have memory located
>> at addresses over 4GB. If you look at the e820 memory map printed at
>> the start of dmesg on bootup and see entries with addresses of
>> 100000000 or higher reported as usable, then this is the case.
>
> Pedro, can you provide your dmesg output, please? I installed 5GB or RAM
> to my machine now, and even with your .config, I can't see the problem.
>
> Daniel
>
>

There you go Daniel.

Pedro

Download attachment "dmesg2.gz" of type "application/x-gzip" (19825 bytes)