Am 19.04.2014 19:33, schrieb Lauri Kasanen:
On Sat, 19 Apr 2014 11:15:53 -0400 Alex Deucher alexdeucher@gmail.com wrote:
On Sat, Apr 19, 2014 at 6:06 AM, Christian König
This was originally un-inlined by Andi Kleen in 2011 citing size concerns. Indeed, a first attempt at inlining it grew radeon.ko by 7%.
However, 2% of cpu is spent in this function. Simply inlining it gave 1% more fps in Urban Terror.
v2: We know the minimum MMIO size. Adding it to the if allows the compiler to optimize the branch out, improving both performance and size.
The v2 patch decreases radeon.ko size by 2%. I didn't re-benchmark, but common sense says perf is now more than 1% better.
Nice!
But are you sure that the register PCI bar is always at least 64K in size? Keep in mind that this code is used over all generations since R100. Additional to that we probably should have a define for that and also apply the optimizations to r100_mm_wreg as well.
Yes, I checked the earlier code. It had 64kb hard-coded, and when it was changed in 2010 to use the dynamic value, the commit said later asics are larger. (07bec2df01)
A quick google also didn't find any dmesg with smaller values, R100 cards had 64kb.
Thanks for digging that up, this indeed sounds valid and like a very nice optimization.
Just as suggested before add a define for this in radeon.h, something like RADEON_MIN_PCI_BAR_SIZE and do the same for r100_mm_wreg as well.
If most of the register accesses are for the interrupt setup, I wonder if it would be better to just clean up the irq_set functions to reduce the register accesses. E.g., only touch the registers for the specific irq masks have changed.
Yes, that should also be done. But as this function is used elsewhere as well, having it fast (not to mention the size decrease) would be good.
I think this patch is safe enough for 3.15, but perhaps it's too late now.
Yeah, probably. But 3.16 should work as well.
Christian.
- Lauri