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SubjectRe: [PATCH net-next v3 01/17] asm: simd context helper API
On Mon, Sep 10, 2018 at 07:08:21PM -0600, Jason A. Donenfeld wrote:
> Sometimes it's useful to amortize calls to XSAVE/XRSTOR and the related
> FPU/SIMD functions over a number of calls, because FPU restoration is
> quite expensive. This adds a simple header for carrying out this pattern:
>
> simd_context_t simd_context = simd_get();
> while ((item = get_item_from_queue()) != NULL) {
> encrypt_item(item, simd_context);
> simd_context = simd_relax(simd_context);
> }
> simd_put(simd_context);
>
> The relaxation step ensures that we don't trample over preemption, and
> the get/put API should be a familiar paradigm in the kernel.

Given that it's always supposed to be used like that, mightn't it be
better if simd_relax() took a pointer to the context, so the call is
just

simd_relax(&simd_context);

?

The inlining means that there won't actually be a pointer dereference in
the emitted code.

If simd_put() also took a pointer then it could set the context back to
HAVE_NO_SIMD as well?

- Kevin

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