Re: [Xen-devel] [Patch][resend] implementation of cpupool support in xl

[Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>]

On 09/16/10 12:45, Ian Campbell wrote:
> On Wed, 2010-09-15 at 08:26 +0100, Juergen Gross wrote:
> > Hi,
> >
> > attached patch implements cpupool support in xl. Rewrite of previous patch
> > after rework of libxl.
> Thanks!
>
> Please could you provide a changelog message? It seems you needed to
> modify the libxc interface in order to support libxl, it would be worth
> commenting on what/why you changed.
Okay, done.

> In several places I notice you calculate (X + 64) / 64. Normally I would
> expect a (X + 63) / 64 pattern to round something up (for example in
> other places you use + 7 / 8). Is this deliberate? Probably worth a
> comment, or maybe wrap the concept into a function with an appropriate
> name?
This was the conversion from max_cpu_id (which is 1 less than the max
number of cpus) to the number of map elements. I've moved this to an own
function for allocating a cpumap.map.

> I think the units of libxl_cpumap.size might be worth a comment too,
> especially since appears to differ from the units used in the libxc
> interface. You can do this in the IDL with e.g.
> -    ("size", uint32),
> +    ("size", uint32, False, "number of<bananas>  in map"),
>       ("map",  Reference(uint64)),
Okay.

> I think<bananas>=="uint64_t sized words"? Perhaps size would be better
> represented as the maximum CPU ID in the map? The fact that the map is
> rounded up to the next 64 bit boundary isn't too interesting to callers,
> is it?
I kept your proposal to keep the size in bytes (like in xc).

> I saw a "size * 8" which I think would better as "size *
> sizeof(*....map)",
The 8 is the number of bits in a byte (size being number of bytes).

> Similarly callers seem to be doing "map[i / 64]&  (i %64)" type
> arithmetic, I think providing a libxl_cpumap_cpu_present helper (and
> _set/_clear if necessary) would help here.
Done that, too.


Juergen

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Juergen Gross                 Principal Developer Operating Systems
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Attachment: xl-pools.patch
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