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 08:16, "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx> 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.

 -- Keir



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