Re: [Xen-devel] PVH dom0 construction timeout

[Jan Beulich <jbeulich@xxxxxxxx>]

On 02.03.2020 10:24, Jan Beulich wrote:
> On 28.02.2020 22:08, Andrew Cooper wrote:
>> page_get_ram_type() is definitely suboptimal here.  We have an linear
>> search over a (large-ish) sorted list, and a caller which has every MFN
>> in the system passed into it, which makes the total runtime of
>> arch_iommu_hwdom_init() quadratic with the size of the system.
> 
> This linear search is the same for PVH and PV, isn't it? In
> fact hwdom_iommu_map(), on the average, may do more work for
> PV than for PVH, considering the is_hvm_domain()-based return
> from the switch()'s default case. So for the moment I could
> explain such a huge difference in consumed time only if the
> PV case ran with iommu_hwdom_passthrough set to true (which
> isn't possible for PVH).

Actually the differing iommu_hwdom_strict setting may matter
here, but it being clear (possible only in the PV case) would
mean more actual mapping operations get carried out, i.e.
should result in slower overall execution. So I'm still
puzzled by the observed difference in consumed time.

Jan

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