Linus Torvalds writes: (Summary) wrote:
Ugh.
Ugh.
A "xor %reg/reg" is two bytes (three for the high regs due to REX prefix). I suspect that a bigger win would be if you try to interleave those "xor" instructions with the "pushq" instructions in the entry code. Because those push instructions tend to be limited by the LSU store bandwidth, so you can probably put in xor instructions almost for free in there.
in there.
Linus
Linus
Linus
[...]
per cycle:Ugh.
Ugh.
A "xor %reg/reg" is two bytes (three for the high regs due to REX prefix). I suspect that a bigger win would be if you try to interleave those "xor" instructions with the "pushq" instructions in the entry code. Because those push instructions tend to be limited by the LSU store bandwidth, so you can probably put in xor instructions almost for free in there.
in there.
Linus
Linus
Linus