linux-kernel - Re: remote debugging via FireWire * __fast_

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Message-Id: <200712040839.39984.ak@suse.de>
Date:	Tue, 4 Dec 2007 08:39:38 +0100
From:	Andi Kleen <ak@...e.de>
To:	Bernhard Kaindl <bkaindl@...i.org>
Cc:	Stefan Richter <stefanr@...6.in-berlin.de>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Bernhard Kaindl <bk@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: remote debugging via FireWire * __fast__ firedump!

On Tuesday 04 December 2007 04:45:22 am Bernhard Kaindl wrote:
>     I just wanted to let you know that I'll have picked up the early
> firewire patch again and cleaned it up very much so that it should
> be ready to submit it and but it on the patch-submission road.

Nice.

> I have just had the guts to explore __fast__ memory dumping over
> firewire for full-system dumps (reading quadlets is __painfully__
> show if you want to read 2GB of memory over the bus, you only get
> about some some kilobytes each second) using raw1394_start_read()
> to allow also block reads instead of just quatlet reads.

Unfortunately it won't work for >3GB or so AFAIK.

> The biggest block size that worked here was 2048 bytes, which was
> enough to get nearly 10MB/s of data transfer rate from the remote
> memory to disk. Dumping 2GB of remote memory was just a matter of
> about 3 few short minutes which quickly ran by.
>
> Afterwards, the victim was dead (I excluded the low MB of memory,
> so something else must have caused this), at least the start of

Did you run into the PCI memory hole below 4GB? 

I suppose the best way would be to require a System.map and
then read e820.nr_map/e820.map[] and only dump real memory.

-Andi
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