Re: [Xen-devel] [PATCH for-4.12] x86: Improve the efficiency of domain_relinquish_resources()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.02.19 at 14:31, <wei.liu2@xxxxxxxxxx> wrote:
> On Thu, Feb 21, 2019 at 12:22:13PM +0000, Andrew Cooper wrote:
>> pci_release_devices() takes the global PCI lock.  Once pci_release_devices()
>> has completed, it will be called redundantly each time paging_teardown() and
>> vcpu_destroy_pagetables() continue.
>> 
>> This is liable to be millions of times for a reasonably sized guest, and is a
>> serialising bottleneck now that domain_kill() can be run concurrently on
>> different domains.
>> 
>> Instead of propagating the opencoding of the relinquish state machine, take
>> the opportunity to clean it up.
>> 
>> Leave a proper set of comments explaining that domain_relinquish_resources()
>> implements a co-routine.  Introduce a documented PROGRESS() macro to avoid
>> latent bugs such as the RELMEM_xen case, and make the new PROG_* states
>> private to domain_relinquish_resources().
>> 
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> 
> Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>



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