Re: Root cause of the issue that HVM guest boots slowly with pvops dom0

[Keir Fraser <keir.fraser@eu.citrix.com>]

On 22/01/2010 08:07, "Yang, Xiaowei" <xiaowei.yang@intel.com> wrote:

>> How does the attached patch work for you? It ought to get you the same
>> speedup as your hack.
> 
> The speed should be almost the same, regardless of twice memcpy.

Did you actually try it out and confirm that?

> Some comments to your trial patch:
> 1.
> diff -r 6b61ef936e69 tools/libxc/xc_private.c
> --- a/tools/libxc/xc_private.c Fri Jan 22 14:50:30 2010 +0800
> +++ b/tools/libxc/xc_private.c Fri Jan 22 15:32:48 2010 +0800

Yes, missed that all-important bit!

> 2. _xc_clean_hcall_buf needs a more careful NULL pointer check.

Not really: free() accepts NULL. But I suppose it would be clearer to put
the free(hcall_buf) inside the if(hcall_buf) block.

> 3. It does modification to 5 out of 73 hypercalls invoking mlock. Other
> problem 
> hypercalls could turn out to be the bottleneck later?:)

The point of a new interface was to be able to do the callers incrementally.
A bit of care is needed on each one, and most are not and probably never
will be bottlenecks.

 -- Keir