Messages in this thread | | | Date | Tue, 15 Sep 2015 10:47:49 +0200 | From | Daniel Lezcano <> | Subject | Re: [RFC PATCH] clocksource: exynos_mct: use container_of() instead of this_cpu_ptr() |
| |
On 09/04/2015 01:49 AM, Alexey Klimov wrote: > Since evt structure is embedded in per-CPU mevt structure it's > definitely faster to use container_of() to get access to mevt > if we have evt (for example as incoming function argument) instead > of more expensive approach with this_cpu_ptr(&percpu_mct_tick). > this_cpu_ptr() on per-CPU mevt structure leads to access to cp15 > to get cpu id and arithmetic operations. > Container_of() is cheaper since it's just one asm instruction. > This should work if used evt pointer is correct and owned by > local mevt structure. > > For example, before this patch set_state_shutdown() looks like: > > 4a4: e92d4010 push {r4, lr} > 4a8: e3004000 movw r4, #0 > 4ac: ebfffffe bl 0 <debug_smp_processor_id> > 4b0: e3003000 movw r3, #0 > 4b4: e3404000 movt r4, #0 > 4b8: e3403000 movt r3, #0 > 4bc: e7933100 ldr r3, [r3, r0, lsl #2] > 4c0: e0844003 add r4, r4, r3 > 4c4: e59400c0 ldr r0, [r4, #192] ; 0xc0 > 4c8: ebffffd4 bl 420 <exynos4_mct_tick_stop.isra.1> > 4cc: e3a00000 mov r0, #0 > 4d0: e8bd8010 pop {r4, pc} > > With this patch: > > 4a4: e92d4010 push {r4, lr} > 4a8: e59000c0 ldr r0, [r0, #192] ; 0xc0 > 4ac: ebffffdb bl 420 <exynos4_mct_tick_stop.isra.1> > 4b0: e3a00000 mov r0, #0 > 4b4: e8bd8010 pop {r4, pc} > > Also, for me size of exynos_mct.o decreased from 84588 bytes > to 83956. > > Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org> > ---
Despite the RFC I applied the patch as it seems simple enough and it has been reviewed by Krzysztof.
-- Daniel
-- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
| |