Am 19.04.2014 19:33, schrieb Lauri Kasanen: > On Sat, 19 Apr 2014 11:15:53 -0400 > Alex Deucher <alexdeucher at gmail.com> wrote: > >> On Sat, Apr 19, 2014 at 6:06 AM, Christian K?nig >>>> 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
