| Message ID | 1441324198-14513-1-git-send-email-alexey.klimov@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 04.09.2015 08:49, 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> > --- > drivers/clocksource/exynos_mct.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) Looks good and sensible. Why you called this RFC? You are not sure if this is correct? One minor nit-pick below, but I am fine without it anyway: Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> > > diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c > index 029f96a..ff44082 100644 > --- a/drivers/clocksource/exynos_mct.c > +++ b/drivers/clocksource/exynos_mct.c > @@ -382,24 +382,28 @@ static void exynos4_mct_tick_start(unsigned long cycles, > static int exynos4_tick_set_next_event(unsigned long cycles, > struct clock_event_device *evt) > { > - struct mct_clock_event_device *mevt = this_cpu_ptr(&percpu_mct_tick); > + struct mct_clock_event_device *mevt; > > + mevt = container_of(evt, struct mct_clock_event_device, evt); > exynos4_mct_tick_start(cycles, mevt); > - Actually I would prefer leaving the empty line here and add such in function below. For me the code is more readable with ending return separated by one line. Best regards, Krzysztof > return 0; > } > > static int set_state_shutdown(struct clock_event_device *evt) > { > - exynos4_mct_tick_stop(this_cpu_ptr(&percpu_mct_tick)); > + struct mct_clock_event_device *mevt; > + > + mevt = container_of(evt, struct mct_clock_event_device, evt); > + exynos4_mct_tick_stop(mevt); > return 0; > } > > static int set_state_periodic(struct clock_event_device *evt) > { > - struct mct_clock_event_device *mevt = this_cpu_ptr(&percpu_mct_tick); > + struct mct_clock_event_device *mevt; > unsigned long cycles_per_jiffy; > > + mevt = container_of(evt, struct mct_clock_event_device, evt); > cycles_per_jiffy = (((unsigned long long)NSEC_PER_SEC / HZ * evt->mult) > >> evt->shift); > exynos4_mct_tick_stop(mevt); > -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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
diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c index 029f96a..ff44082 100644 --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -382,24 +382,28 @@ static void exynos4_mct_tick_start(unsigned long cycles, static int exynos4_tick_set_next_event(unsigned long cycles, struct clock_event_device *evt) { - struct mct_clock_event_device *mevt = this_cpu_ptr(&percpu_mct_tick); + struct mct_clock_event_device *mevt; + mevt = container_of(evt, struct mct_clock_event_device, evt); exynos4_mct_tick_start(cycles, mevt); - return 0; } static int set_state_shutdown(struct clock_event_device *evt) { - exynos4_mct_tick_stop(this_cpu_ptr(&percpu_mct_tick)); + struct mct_clock_event_device *mevt; + + mevt = container_of(evt, struct mct_clock_event_device, evt); + exynos4_mct_tick_stop(mevt); return 0; } static int set_state_periodic(struct clock_event_device *evt) { - struct mct_clock_event_device *mevt = this_cpu_ptr(&percpu_mct_tick); + struct mct_clock_event_device *mevt; unsigned long cycles_per_jiffy; + mevt = container_of(evt, struct mct_clock_event_device, evt); cycles_per_jiffy = (((unsigned long long)NSEC_PER_SEC / HZ * evt->mult) >> evt->shift); exynos4_mct_tick_stop(mevt);
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> --- drivers/clocksource/exynos_mct.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)