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

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