Re: page fault scalability patch V12 [0/7]: Overview and performance tests

[Jeff Garzik <jgarzik@pobox.com>]

Andrew Morton wrote:
> We need an -rc3 yet.  And I need to do another pass through the
> regressions-since-2.6.9 list.  We've made pretty good progress there
> recently.  Mid to late December is looking like the 2.6.10 date.


another for that list, BTW:

I am currently chasing a 2.6.8->2.6.9 SATA regression, which causes 
ata_piix (Intel ICH5/6/7) to not-find some SATA devices on x86-64 SMP, 
but works on UP.  Potentially related to >=4GB of RAM.



Details, in case anyone is interested:
Unless my code is screwed up (certainly possible), PIO data-in [using 
the insw() call] seems to return all zeroes on a true-blue SMP machine, 
for the identify-device command.  When this happens, libata (correctly) 
detects a bad id page and bails.  (problem doesn't show up on single CPU 
w/ HT)

What changed from 2.6.8 to 2.6.9 is

2.6.8:
	bitbang ATA taskfile registers (loads command)
	bitbang ATA data register (read id page)

2.6.9:
	bitbang ATA taskfile registers
	queue_work()
	workqueue thread bitbangs ATA data register (read id page)

So I wonder if <something> doesn't like CPU 0 sending I/O traffic to the 
on-board SATA PCI device, then immediately after that, CPU 1 sending I/O 
traffic.

Anyway, back to debugging...  :)

	Jeff