[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86: introduce specialized clear_page()
On 19/6/07 11:16, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote: > While the patch also adds an SSE version, this is is currently orphaned > as I am not certain about the benefit of special casing idle VCPUs in > a few places (during context switching), so that at least in that > context using %xmmN registers would be possible without crashing and/or > corrupting guest state. The benefit of adding such support could be to > reduce scheduling latency when a VCPU is to transition out of idle, but > is busy doing page cleaning. I measure no benefit from the XMM version (nor from upgrading the SSE2 version on x86/64 to clear from %rax instead of %eax). I guess this is because the move is non-temporal and it's actually quite easy to max the memory bandwidth. So I stripped out the xmm version (it can't work anyway without some kernel_fpu_begin/end kind of mechanism) and made the sse2 version common across i386 and x86_64 since that was easily done and increases code sharing. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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