RE: [Xen-devel] [PATCH] Optimizing x86-64 xenlinux using global pagesfor user mode (take 2)

["Nakajima, Jun" <jun.nakajima@xxxxxxxxx>]

Andrew Theurer wrote:
> Ian Pratt wrote:
>>> The previous patch had a problem with the builder, which constructs
>>> the initial page tables with the USER bit on. And Xen couldn't
>>> distinguish kernel or use pages. It was partially checked avoiding
>>> the bug, and it's finished with this patch.
>> 
>> Thanks. Have you any updated benchmark numbers as the bug could have
>> been giving quite a performance boost before.

Looks like part of the boost was realized by the bug, but I still see
consistent and visible improvements with lmbench. If I turn on the
global bits for the kernel pages as well, I see more improvements, which
are comparable with or better than before. I think we need to do macro
benchmarks to see how this helps. 

> 
> FWIW, I had been running more extensive testing on changeset 11225
> (before global-bit) and 11229 (global-bit with revert/fix for dom0
> builder), and they do not match the initial testing I did with rev
> 11118 + global_1 patch.  In fact, I am not seeing really any
> improvement.  I am not sure what is wrong.  Should I just test
> xen-unstable-tip+newest_patch and see where we stand?
> 

Yes, please. You shouldn't have observed any performance difference
between 11225 and 11229 because the changeset 11226 did not enable the
global bit. 

> -Andrew Theurer

Jun
---
Intel Open Source Technology Center

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