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