On Thu, May 26, 2011 at 09:29:51AM -0400, Nicolas Pitre wrote: > On Thu, 26 May 2011, Dave Martin wrote: > > > > The core logic spans 5 instructions. Only 3 of them are actually the > > > same in both cases i.e. those with no references to 1b or 2b, and > > > they're perfectly interlaced in between the others. Trying to make this > > > into common runtime code would result in even bigger code I'm afraid. > > > This could be made into common source code via a macro though. > > > > Fair enough -- a macro might be worth a try _if_ it simplifies things > > in the source, but I think you're right that merging the actual code > > probably isn't worth it just to save a few words in the vectors page > > (which eats up 4K regardless of what we put in it) and a few cycles per > > fault (which already costs many, many cycles). > > In the normal cases, there is no additional cycles per fault as the > inline check remains unchanged, and it goes like this: > > @ Make sure our user space atomic helper is restarted > @ if it was interrupted in a critical region. Here we > @ perform a quick test inline since it should be false > @ 99.9999% of the time. The rest is done out of line. > cmp r2, #TASK_SIZE > blhs kuser_cmpxchg_fixup > > In most cases the branch is not taken.
True! ---Dave _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
