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

["Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx>]

Keir Fraser wrote:
> On 22/01/2010 08:07, "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx> 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?
Yes, I tried it out. And there are no obvious speed difference comparing your 
patch (my comment 1 included) and the hack.
> > 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.
Agree. Anyway when we meet other pvops performance issue later, let's go back 
and have a check at this aspect.
Thanks,
xiaowei



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