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@xxxxxxxxxx>
---
Despite the RFC I applied the patch as it seems simple enough and it has
been reviewed by Krzysztof.
-- Daniel
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