Re: [Xen-devel] [PATCH v6 for Xen 4.7 4/4] xl: enable per-VCPU parameter settings for RTDS scheduler

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Mar 08, 2016 at 03:24:35PM -0600, Chong Li wrote:
[...]
> >> +    case 'v':
> >> +        if (!strcmp(optarg, "all")) { /* get or set all vcpus of a domain 
> >> */
> >> +            opt_all = 1;
> >> +            break;
> >> +        }
> >> +        if (v_index >= v_size) { /* vcpus array is full */
> >> +            v_size *= 2;
> >> +            vcpus = xrealloc(vcpus, v_size);
> >> +        }
> >> +        vcpus[v_index++] = strtol(optarg, NULL, 10);
> >> +        opt_v = 1;
> >> +        break;
> >
> > I'm still not quite sure why this is written like this. What's the
> > expected syntax of this command? The hunk to patch xl manpage is very
> > terse...
> 
> We have three arrays here, vcpus[], periods[] and budgets[]. If the xl
> command is like (more examples at cover letter):
> 
> xl sched-rtds -d vm1 -v 3 -p 500 -b 200 -v 1 -p 600 -b 300 (set the
> scheduling parameters of two vcpus of vm1)
> 
> then, the three arrays would be like:
> 
> vcpus: [3, 1]
> periods: [500, 600]
> budgets: [200, 300]
> 
> What makes this code complicated is the size of these three arrays
> grows along with the
> reading of OPTS. At the beginning, all three arrays have the size for
> only one int. When
> one array becomes full, we double its size.

OK. In that case, please:

1. Introduce a helper function to double the size of the array.
2. Improve manual a bit, maybe with one or two examples.

Wei.

> 
> Chong
> 
> 
> 
> -- 
> Chong Li
> Department of Computer Science and Engineering
> Washington University in St.louis

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