Hello, Nick. How have you been? :) On Wed, Sep 21, 2016 at 08:57:11PM +1000, Nicholas Piggin wrote: > On Wed, 21 Sep 2016 18:51:37 +1000 > Nicholas Piggin <npiggin@xxxxxxxxx> wrote: > > > Some architectures require an additional load to find the address of > > percpu pointers. In some implemenatations, the C aliasing rules do not > > allow the result of that load to be kept over the store that modifies > > the percpu variable, which causes additional loads. > > Sorry I picked up an old patch here. This one should be better. > > From d0cb9052d6f4c31d24f999b7b0cecb34681eee9b Mon Sep 17 00:00:00 2001 > From: Nicholas Piggin <npiggin@xxxxxxxxx> > Date: Wed, 21 Sep 2016 18:23:43 +1000 > Subject: [PATCH] percpu: improve generic percpu modify-return implementations > > Some architectures require an additional load to find the address of > percpu pointers. In some implemenatations, the C aliasing rules do not > allow the result of that load to be kept over the store that modifies > the percpu variable, which causes additional loads. > > Work around this by finding the pointer first, then operating on that. > > It's also possible to mark things as restrict and those kind of games, > but that can require larger and arch specific changes. > > On powerpc, __this_cpu_inc_return compiles to: > > ld 10,48(13) > ldx 9,3,10 > addi 9,9,1 > stdx 9,3,10 > ld 9,48(13) > ldx 3,9,3 > > With this patch it compiles to: > > ld 10,48(13) > ldx 9,3,10 > addi 9,9,1 > stdx 9,3,10 > > Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx> Patch looks good to me but seems QP encoded. Can you please resend? Thanks and it's great to see you again! -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
