Re: [Xen-devel] Converting heap page_infos to contiguous virtual

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Jul 15, 2016 at 10:53:51AM -0400, Boris Ostrovsky wrote:
> On 07/14/2016 09:29 AM, Andrew Cooper wrote:
> >
> > However, I would recommend getting something functioning first, before
> > trying to optimise it.
> 
> There are two fairly independent parts to improving scrubbing: one is
> making it asynchronous and second is improving clear_page() performance.
> Whole-RAM mapping is needed for the latter.

Attaching a nice graph of different memset on Broadwell (credits go to
Joao for doing the testing). Skylake is 10% faster than Broadwell.


> 
> >
> > There is probably a lot to be gained simply by improving clear_page().
> 
> The biggest improvement comes from switching to AVX(2) when available.
> It's been a while since I ran those tests so I will have to re-measure
> it but my recollection is that 4K was too small to see significant changes.
> 
> A potential improvement might come from dropping (or, rather, deferring)
> sfence in clear_page_sse2. I don't know how much this would buy us though.
> 
> -boris
> 
> 
> 
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