Re: [Xen-devel] Root cause of the issue that HVM guest boots slowly with pvops dom0

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 21/01/2010 08:44, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

>> - Limiting vCPU# of dom0 is always an easiest one - you may call it
>> workaround
>> rather than a solution:) It not only reduces the total # of resched IPI ( =
>> mlock# * (vCPU#-1)), but reduces the cost of each handler - because of
>> spinlock. 
>> But the impact is still there, more or less, when vCPU# > 1.
>> 
>> - To remove mlock, another sharing method is needed between dom0 user space
>> app
>> and Xen HV.
> 
> A pre-mlock()ed memory page for small (sub-page) hypercalls? Protected with
> a semaphore: failure to acquire semaphore means take slow path. Have all
> hypercallers in libxc launder their data buffers through a new interface
> that tries to grab and copy into the pre-allocated buffer.

I'll sort out a trial patch for this myself.

 Thanks,
 Keir



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