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

From	Ingo Molnar <mingo@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues
Date	2016-04-30 10:00 +0200
Message-ID	<rtxYL-3Vo-7@gated-at.bofh.it> (permalink)
References	(2 earlier) <rtmTE-3yl-13@gated-at.bofh.it> <rtmTE-3yl-11@gated-at.bofh.it> <rtn3k-3Ce-15@gated-at.bofh.it> <rtncZ-3HL-1@gated-at.bofh.it> <rtnwn-3Q2-25@gated-at.bofh.it>
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* 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

Thread

Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Dave Hansen <dave.hansen@linux.intel.com> - 2016-04-29 20:10 +0200
  Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Ingo Molnar <mingo@kernel.org> - 2016-04-29 21:50 +0200
  Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Dave Hansen <dave.hansen@linux.intel.com> - 2016-04-29 22:10 +0200
    Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-04-29 22:20 +0200
      Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Andy Lutomirski <luto@amacapital.net> - 2016-04-29 22:30 +0200
        Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Dave Hansen <dave.hansen@linux.intel.com> - 2016-04-29 22:50 +0200
          Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Andy Lutomirski <luto@amacapital.net> - 2016-04-29 22:50 +0200
            Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Dave Hansen <dave.hansen@linux.intel.com> - 2016-04-30 00:50 +0200
          Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Ingo Molnar <mingo@kernel.org> - 2016-04-30 10:00 +0200
            Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Dave Hansen <dave.hansen@linux.intel.com> - 2016-05-02 18:30 +0200
              Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Ingo Molnar <mingo@kernel.org> - 2016-05-02 20:40 +0200
      Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Dave Hansen <dave.hansen@linux.intel.com> - 2016-04-29 22:40 +0200
  Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-04-29 22:10 +0200

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