[PATCH] Add ifunc memcpy and memmove for aarch64

Tue Feb 7 13:22:00 GMT 2017


On 07/02/2017 11:01, Siddhesh Poyarekar wrote:
> On Tuesday 07 February 2017 06:12 PM, Wilco Dijkstra wrote:
>> I agree we want to avoid using conditional compilation as much as possible.
>> On the other hand duplication is a bad idea too, I've seen too many cases where
>> bugs were only fixed in one of the N duplicates.
> 
> Sure, but then in that case the de-duplication must be done by
> identifying a logical code block and make that into a macro to override
> and not just arbitrarily inject hunks of code.  So in this case it could
> be alternate implementations of copy_long that is sufficient so #define
> COPY_LONG in both memcpy_generic and memcpy_thunderx and have the parent
> (memcpy.S) use that macro.  In fact, that might even end up making the
> code a bit nicer to read.
> 
>> However I'm actually wondering whether we need an ifunc for this case.
>> For large copies from L2 I think adding a prefetch should be benign even on 
>> cores that don't need it, so if the benchmarks confirm this we should consider
>> updating the generic memcpy.
> 
> That is a call that ARM maintainers can take and is also another reason
> to separate the IFUNC infrastructure code from the thunderx change.

I checked only the memcpy change on a APM X-Gene 1 and results seems to show
improvements on aligned input, at least for sizes shorter thatn 4MB.  I would
like to check on more armv8 chips, but it does seems a nice improvement
over generic implementation.
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                       	memcpy
Length 65543, alignment  0/ 0:	4553.71
Length 65551, alignment  0/ 3:	11239.8
Length 65567, alignment  3/ 0:	11201.6
Length 65599, alignment  3/ 5:	11221.2
Length 131079, alignment  0/ 0:	9023.67
Length 131087, alignment  0/ 3:	22489.5
Length 131103, alignment  3/ 0:	22439.6
Length 131135, alignment  3/ 5:	22426.3
Length 262151, alignment  0/ 0:	21198.5
Length 262159, alignment  0/ 3:	48474
Length 262175, alignment  3/ 0:	48292.3
Length 262207, alignment  3/ 5:	48545.1
Length 524295, alignment  0/ 0:	43480.7
Length 524303, alignment  0/ 3:	93729.3
Length 524319, alignment  3/ 0:	93706.8
Length 524351, alignment  3/ 5:	93809.2
Length 1048583, alignment  0/ 0:	86732.2
Length 1048591, alignment  0/ 3:	187419
Length 1048607, alignment  3/ 0:	187153
Length 1048639, alignment  3/ 5:	187384
Length 2097159, alignment  0/ 0:	173630
Length 2097167, alignment  0/ 3:	373671
Length 2097183, alignment  3/ 0:	373776
Length 2097215, alignment  3/ 5:	374153
Length 4194311, alignment  0/ 0:	383575
Length 4194319, alignment  0/ 3:	752044
Length 4194335, alignment  3/ 0:	750919
Length 4194367, alignment  3/ 5:	751680
Length 8388615, alignment  0/ 0:	1.24695e+06
Length 8388623, alignment  0/ 3:	1.6407e+06
Length 8388639, alignment  3/ 0:	1.63961e+06
Length 8388671, alignment  3/ 5:	1.6407e+06
Length 16777223, alignment  0/ 0:	2.7774e+06
Length 16777231, alignment  0/ 3:	3.34092e+06
Length 16777247, alignment  3/ 0:	3.33036e+06
Length 16777279, alignment  3/ 5:	3.33811e+06
Length 33554439, alignment  0/ 0:	5.4628e+06
Length 33554447, alignment  0/ 3:	6.56429e+06
Length 33554463, alignment  3/ 0:	6.56451e+06
Length 33554495, alignment  3/ 5:	6.5654e+06
-------------- next part --------------
                       	memcpy
Length 65543, alignment  0/ 0:	5590.23
Length 65551, alignment  0/ 3:	11171
Length 65567, alignment  3/ 0:	11146.2
Length 65599, alignment  3/ 5:	11154.1
Length 131079, alignment  0/ 0:	11109
Length 131087, alignment  0/ 3:	22266.3
Length 131103, alignment  3/ 0:	22296.1
Length 131135, alignment  3/ 5:	22257.1
Length 262151, alignment  0/ 0:	22780.6
Length 262159, alignment  0/ 3:	46212.7
Length 262175, alignment  3/ 0:	45999.7
Length 262207, alignment  3/ 5:	46221.3
Length 524295, alignment  0/ 0:	47787.3
Length 524303, alignment  0/ 3:	93263.7
Length 524319, alignment  3/ 0:	93028.3
Length 524351, alignment  3/ 5:	93301.5
Length 1048583, alignment  0/ 0:	95413.2
Length 1048591, alignment  0/ 3:	186367
Length 1048607, alignment  3/ 0:	185780
Length 1048639, alignment  3/ 5:	186296
Length 2097159, alignment  0/ 0:	190546
Length 2097167, alignment  0/ 3:	372310
Length 2097183, alignment  3/ 0:	371187
Length 2097215, alignment  3/ 5:	372281
Length 4194311, alignment  0/ 0:	379009
Length 4194319, alignment  0/ 3:	736763
Length 4194335, alignment  3/ 0:	733672
Length 4194367, alignment  3/ 5:	736531
Length 8388615, alignment  0/ 0:	1.26684e+06
Length 8388623, alignment  0/ 3:	1.61883e+06
Length 8388639, alignment  3/ 0:	1.6062e+06
Length 8388671, alignment  3/ 5:	1.61872e+06
Length 16777223, alignment  0/ 0:	2.68259e+06
Length 16777231, alignment  0/ 3:	3.24415e+06
Length 16777247, alignment  3/ 0:	3.23356e+06
Length 16777279, alignment  3/ 5:	3.2449e+06
Length 33554439, alignment  0/ 0:	5.47245e+06
Length 33554447, alignment  0/ 3:	6.56719e+06
Length 33554463, alignment  3/ 0:	6.55255e+06
Length 33554495, alignment  3/ 5:	6.56698e+06
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