Re: [Xen-devel] [PATCH v6 2/2] xen: move TLB-flush filtering out into populate_physmap during vm creation

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Sep 20, 2016 at 06:39:32PM -0700, Dongli Zhang wrote:
> > > This patch implemented parts of TODO left in commit id
> > > a902c12ee45fc9389eb8fe54eeddaf267a555c58 (More efficient TLB-flush
> > > filtering in alloc_heap_pages()). It moved TLB-flush filtering out into
> > > populate_physmap. Because of TLB-flush in alloc_heap_pages, it's very slow
> > > to create a guest with memory size of more than 100GB on host with 100+
> > > cpus.
> > >
> > >
> > Do you have some actual numbers on how much faster after applying this
> > patch?
> > 
> > This is mostly for writing release note etc, so it is fine if you don't
> > have numbers at hand.
> 
> I do not have data of upstream version at hand now.  I always tested the
> performance of this patchset by backporting it to an Oracle VM based on a
> very old Xen version, before I sent out the patchset for review. The
> backport just involves: (1) copy & paste code, (2) change bool to bool_t
> and (3) change true/false to 1/0.
> 
> The test machine has 8 nodes of 2048GB memory and 128 cpu. With this
> patchset applied, the time to re-create a VM (with 135GB memory and 12
> vcpu) is reduced from 5min to 20s.

Thanks, this is useful information.

Wei.

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