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SubjectRe: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues

* Dave Hansen <dave.hansen@linux.intel.com> wrote:

> But I also think it would be pretty nice if 'ls' didn't pay the 2k cost to have
> AVX-512 state if it's not using AVX-512. [...]

A C library might decide to use AVX-512 memset(). RAM is cheap, while allocation
complexity, especially in the kernel, has various other costs.

I mean, we should not worry about per thread allocation sizes that can be compared
to the kernel stack size.

We can still use the compacted area handling instructions, because presumably
those are the fastest and are also the most optimized ones? But I wouldn't use
them to do dynamic allocation: just allocate the maximum possible FPU save area at
task creation time and never again worry about that detail.

Ok?

Thanks,

Ingo

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