Sparc slowdown - problem identified...

Harti Brandt brandt at
Fri Aug 15 07:58:48 PDT 2003

On Fri, 15 Aug 2003, Thomas Moestl wrote:

TM>On Fri, 2003/08/15 at 12:20:39 +0200, Harti Brandt wrote:
TM>> Hi all,
TM>> it seems I have identified which commit causes the slow down on some
TM>> sparcs. The kernel from just before that commit works just fine, the
TM>> kernel from just after it is 3x slower on my Ultra-10 (as was also
TM>> reported by others). I have no idea why that happens. The only difference
TM>> in the time -l report is user and system time going up by a factor of
TM>> three and the involuntary context switches doubling.
TM>It seems that deferred errors (and thus the data access errors
TM>generated due to PCI bus timeouts from non-existant devices) will
TM>disable the instruction and data cache by resetting the corresponding
TM>enable bits in the LSU control register, and the current code fails to
TM>reenable them (which also requires a cache flush). A simple workaround
TM>for now is to avoid triggering these errors, so enabling OFW_NEWPCI
TM>should help.

I can confirm that it helps. I assume that OFW_NEWPCI is currently there
to allow testing and one day to throw the switch and remove the old stuff?
Wouldn't it help to make it the default? Otherwise the testing will be
rather limited.

harti brandt,
brandt at, harti at

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