On 01/05/2016 02:18 PM, Eric Dumazet wrote:
> On Tue, 2016-01-05 at 10:41 -0800, Tom Herbert wrote:
>> Implement assembly routine for csum_partial for 64 bit x86. This
>> primarily speeds up checksum calculation for smaller lengths such as
>> those that are present when doing skb_postpull_rcsum when getting
>> CHECKSUM_COMPLETE from device or after CHECKSUM_UNNECESSARY
>> conversion.
>
> Very nice !
>
>
> You might add a comment telling the '4' comes from length of 'adcq
> 6*8(%rdi),%rax' instruction, and that the 'nop' is to compensate that
> 'adcq 0*8(%rdi),%rax' is using 3 bytes instead.
>
> We also could use .byte 0x48, 0x13, 0x47, 0x00 to force a 4 bytes
> instruction and remove the nop.
>
Apparently "adcq.d8" will do The Right Thing for this.
-hpa
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