82xx performance

[Rune Torgersen]

> This is certainly significant, but a lot has happened between the two
> versions. I few ideas:
> 
> * compare some of the key configuration options:
>   # CONFIG_DEBUG_*
>   # CONFIG_PREEMPT*
>   # CONFIG_NO_HZ
>   # CONFIG_HZ

2.6.25:
# CONFIG_DEBUG_DRIVER is not set
# CONFIG_DEBUG_DEVRES is not set
# CONFIG_DEBUG_FS is not set
CONFIG_DEBUG_KERNEL=y
# CONFIG_DEBUG_SHIRQ is not set
# CONFIG_DEBUG_RT_MUTEXES is not set
# CONFIG_DEBUG_SPINLOCK is not set
# CONFIG_DEBUG_MUTEXES is not set
# CONFIG_DEBUG_SPINLOCK_SLEEP is not set
# CONFIG_DEBUG_LOCKING_API_SELFTESTS is not set
# CONFIG_DEBUG_KOBJECT is not set
# CONFIG_DEBUG_HIGHMEM is not set
CONFIG_DEBUG_BUGVERBOSE=y
CONFIG_DEBUG_INFO=y
# CONFIG_DEBUG_VM is not set
# CONFIG_DEBUG_LIST is not set
# CONFIG_DEBUG_SG is not set
# CONFIG_DEBUG_STACKOVERFLOW is not set
# CONFIG_DEBUG_STACK_USAGE is not set
# CONFIG_DEBUG_PAGEALLOC is not set
# CONFIG_DEBUGGER is not set

# CONFIG_PREEMPT_NONE is not set
# CONFIG_PREEMPT_VOLUNTARY is not set
CONFIG_PREEMPT=y
# CONFIG_PREEMPT_RCU is not set

# CONFIG_NO_HZ is not set
# CONFIG_HZ_100 is not set
# CONFIG_HZ_250 is not set
# CONFIG_HZ_300 is not set
CONFIG_HZ_1000=y
CONFIG_HZ=1000


2.6.18:
# CONFIG_DEBUG_DRIVER is not set
CONFIG_DEBUG_KERNEL=y
# CONFIG_DEBUG_SLAB is not set
# CONFIG_DEBUG_RT_MUTEXES is not set
# CONFIG_DEBUG_SPINLOCK is not set
# CONFIG_DEBUG_MUTEXES is not set
# CONFIG_DEBUG_RWSEMS is not set
# CONFIG_DEBUG_SPINLOCK_SLEEP is not set
# CONFIG_DEBUG_LOCKING_API_SELFTESTS is not set
# CONFIG_DEBUG_KOBJECT is not set
CONFIG_DEBUG_INFO=y
# CONFIG_DEBUG_FS is not set
# CONFIG_DEBUG_VM is not set

# CONFIG_PREEMPT_NONE is not set
# CONFIG_PREEMPT_VOLUNTARY is not set
CONFIG_PREEMPT=y
CONFIG_PREEMPT_BKL=y

# CONFIG_HZ_100 is not set
# CONFIG_HZ_250 is not set
CONFIG_HZ_1000=y
CONFIG_HZ=1000


> 
> * Try looking at where the time is spent, using oprofile or 
> readprofile

Doing this now.
> 
> * Try setting /proc/sys/kernel/compat/sched_yield to 1, to 
> get the legacy
> behaviour of the scheduler.

Made perfromance on .25 a few percent worse. (84 minutes on kernel
compile instead of 81 minutes)
 
> * Maybe there is a kernel version that supports your hardware in both
> arch/ppc/ and arch/powerpc. In that case, you could see if 
> the platform
> change had an impact.

Will try. Last port in ppc branch was 2.6.18 and first in powerpc was
2.6.24.
I should be able to port ppc to .25 also I think.

Thanks!