On 2017/05/04 22:50, Tom Herbert wrote:
> Hi,
>
> I am thinking about the possibility of using SSE in kernel for
> speeding up the kernel memcpy particularly for copy to userspace
> emeory, and maybe even using the string instructions (like if we
> supported regex in something like eBPF). AFAIK we don't use SSE in
> kernel because of xmm register state needing to be saved across
> context switch. However, if we start busy-polling a CPU in kernel on
> network queues then there might not be any context switches to worry
> about. In this model we'd want to enable SSE per CPU.
>
> Has this ever been tried before? Is this at all feasible? :-) Is it
> possible to enable SSE for kernel for just one CPU? (I found CPUID
> will return SSE supported, but don't see how to enable other than
> -msse for compiling).
This reminds me of what you tried in
c6e1a0d12ca7 net: Allow no-cache copy from user on transmit
(v3.0-rc1)
and that I reverted in
cdb3f4a31b64 net: Do not enable tx-nocache-copy by default
(v3.14-rc1)
Sure, it's not exactly the same thing...
