Messages in this thread | | | Date | Mon, 12 Apr 2010 12:48:58 +0200 | From | Daniel Mack <> | Subject | Re: [LKML] Re: USB transfer_buffer allocations on 64bit systems |
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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@rowland.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
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