Re: [Xen-devel][PATCH] libxc bitmap utils and vcpu-affinity

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

No changeset comment. No signed-off-by line. It actually bloats the
libraries by a net 650 LOC (747 added, 87 deleted according to diffstat).
And below I append the very first function I read: it doesn't inspire
confidence that the implementation is over-complicated/long and
unnecessarily handles 16-bit values. Why should I show your patch some love?

 -- Keir

+static inline int __xc_ffs(uint8_t byte)
+{
+       int num = 0;
+
+       if ((byte & 0xff) == 0) {
+               num += 8;
+               byte >>= 8;
+       }
+       if ((byte & 0xf) == 0) {
+               num += 4;
+               byte >>= 4;
+       }
+       if ((byte & 0x3) == 0) {
+               num += 2;
+               byte >>= 2;
+       }
+       if ((byte & 0x1) == 0)
+               num += 1;
+       return num;
+}

On 30/03/2010 15:42, "Dulloor" <dulloor@xxxxxxxxx> wrote:

> Resubmitting the patch.
> 
> -dulloor
> 
> ---------- Forwarded message ----------
> From: Dulloor <dulloor@xxxxxxxxx>
> Date: Tue, Mar 23, 2010 at 12:55 PM
> Subject: Re: [Xen-devel][PATCH] libxc bitmap utils and vcpu-affinity
> To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
> Cc: Jan Beulich <JBeulich@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx"
> <xen-devel@xxxxxxxxxxxxxxxxxxx>
> 
> 
> Please use this patch, in which length of bitmap is
> (physinfo.max_cpu_id+1), rather than (physinfo.nr_cpus).
> 
> -dulloor
> 
> On Tue, Mar 23, 2010 at 12:41 PM, Dulloor <dulloor@xxxxxxxxx> wrote:
>> I meant utils for **xenctl_cpumap**
>> 
>> On Tue, Mar 23, 2010 at 12:40 PM, Dulloor <dulloor@xxxxxxxxx> wrote:
>>> Fine, I agree with you both. Attached is a patch adding utils for
>>> xenctl_bitmap (to libxc) and using the same in vcpu_(get|set)affinity.
>>> For the guest-numa interface, I will see if I can use xenctl_cpumap.
>>> 
>>> -dulloor
>>> 
>>> On Tue, Mar 23, 2010 at 7:05 AM, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
>>> wrote:
>>>> On 23/03/2010 10:10, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>>>> 
>>>>>>>> Dulloor <dulloor@xxxxxxxxx> 22.03.10 18:44 >>>
>>>>>> Motivation for using xenctl_cpumask in Xen interfaces :
>>>>>> - xenctl_cpumap is just 4 bytes smaller than static xenctl_cpumask for
>>>>>> 128 cpus (128 would be good for quite some time). However, the new
>>>>> 
>>>>> I don't buy this (we're already building for 256 CPUs, looking forward
>>>>> to further bump this in the not too distant future), and I'm generally
>>>>> opposed to introducing hard coded limits in a public interface.
>>>> 
>>>> We should use xenctl_cpumask everywhere for specifying physical CPU
>>>> bitmaps,
>>>> even into guest NUMA interfaces if appropriate. I don't really care if it
>>>> is
>>>> a bit harder to use than a static bitmap.
>>>> 
>>>>  -- Keir
>>>> 
>>>> 
>>>> 
>>> 
>> 



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