ATA_CAM + ZFS gives short 1-2 seconds system freeze on disk load

[Guido Falsi]

On Mon, Feb 08, 2010 at 03:41:14PM +0100, Ivan Voras wrote:
> On 02/08/10 15:33, Guido Falsi wrote:
> 
> >It looks like it freezes the system for the second or two it takes
> >to flush buffers to disk when there are big outputs. This happens
> >when decompressiong big distfiles, mainly. The openoffice port
> >triggers this almost continuosly every few seconds during compilation.
> >I've also seen this when working with big files(for example graphic
> >images in uncompressed formats).
> >
> >It gets very annoying and I don't remember this happening before
> >activating the ATA_CAM flag. There was some slowdown with big disk
> >access, but not a total freeze.
> 
> I think ZFS does this all the time, i.e. regardless of underlying
> device drivers. Can you test your theory by going to an older kernel
> and keeping *everything* else the same?

I have made the test and in fact I see the same freezes without ATA_CAM
and the legacy ata system.

Maybe my idea was due to selective memory :)

The other problem at boot still exists with ATA_CAM and does not without
it.

I'll create a new thread about this as suggested by Jeremy Chadwick.

-- 
Guido Falsi <mad at madpilot.net>