[PATCH 1/2] UBUNTU: [Config] enable MMIOTRACE for graphics debugging

Scott James Remnant scott at ubuntu.com
Thu Mar 18 16:50:15 UTC 2010

On Thu, 2010-03-18 at 16:43 +1100, Christopher James Halse Rogers wrote:

> On Wed, 2010-03-17 at 03:03 -0700, Bryce Harrington wrote:
> > On Wed, Mar 17, 2010 at 09:26:24AM +0000, Andy Whitcroft wrote:
> > > Enable MMIOTRACE to allow us to trace low level card operations.  This is
> > > commonly used to debug graphics issues particularly under Nouveau.
> > > According to the documentation it is a near zero impact when disabled.
> > 
> > "when enabled" I hope?
> > 
> No; when it's enabled it's a huge performance hit.  It's not uncommon
> for a mmio-traced nvidia blob to take multiple minutes to bring up X.
To be clear here:

The kernel config option, when enabled, adds a new available tracer,
which when itself is enabled, causes a huge performance hit.

Enabling the kernel config option doesn't cause a huge performance hit
in its own right.

Scott James Remnant
scott at ubuntu.com
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