On Sunday, May 18, 2008 9:48 pm Hidetoshi Seto wrote:

Jesse Barnes wrote:

quoted

Since we know MSI is a problem, let's just go with fixing that for now. 
If we find that other caps are also causing problems we can revisit
caching all of them; the patch is simple enough.

Humm...
I suppose it can be more simple. How about this patch?

quoted

everytime handle_edge_irq is called it needs to mask and unmask MSI, and
that leads to a series of very expensive calls to pci_find_capability

The position of MSI capability is already cached in the msi_desc when
we enter the msi_set_mask_bits().  Use it instead.

Signed-off-by: Hidetoshi Seto <redacted>

Yeah, this looks really nice.  It should also fix Arnaldo's latency problem, 
and really looks like a bug fix for the MSI code more than anything.

Arnaldo, can you take a look & test and ack/nack?

Thanks,
Jesse