Re: remote debugging via FireWire * __fast__ firedump!

Andi Kleen
2007-12-04T21:16:43Z

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