On Mon, May 26, 2014 at 1:13 PM, Yu, Fenghua <fenghua...@intel.com> wrote: >> From: Andy Lutomirski [mailto:l...@amacapital.net] >> On 05/26/2014 10:01 AM, Fenghua Yu wrote: >> > From: Fenghua Yu <fenghua...@intel.com> >> > >> > With ever growing extended state registers (xstate) on x86 processors, >> kernel >> > needs to cope with issue of growing memory space occupied by xstate. >> The xsave >> > area is holding more and more xstate registers, growing from legacy >> FP and >> > SSE to AVX, AVX2, AVX-512, MPX, and Intel PT. >> > >> > The recently introduced compacted format of xsave area saves xstates >> only >> > for enabled states. This patch set saves the xsave area space per >> process >> > in compacted format by xsaves/xrstors instructions. >> >> Are we going to want to encourage userspace to do something like >> sticking vzeroupper right before each syscall to make any >> xsaves/xrestores faster? > > This patch set allow compacted format in kernel and standard format > in user space. This works fine for both kernel and user application.
My question is purely about optimization: if userspace does a blocking system call, will it be significantly faster if userspace zeros out as much of the extended state as possible before doing the system call? I think I tried this once with xsaveopt and decided that it didn't make much of a difference. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
