Re: [PATCH v7 for Xen 4.7 3/4] libxl: enable per-VCPU parameter settings for RTDS scheduler

[Wei Liu <wei.liu2@citrix.com>]

On Wed, Mar 16, 2016 at 11:47:50AM -0500, Chong Li wrote:
> Add libxl_vcpu_sched_params_get/set and sched_rtds_vcpu_get/set
> functions to support per-VCPU settings.
> 
> Signed-off-by: Chong Li <chong.li@wustl.edu>
> Signed-off-by: Meng Xu <mengxu@cis.upenn.edu>
> Signed-off-by: Sisu Xi <xisisu@gmail.com>
> 

Good work fixing all issues.

Acked-by: Wei Liu <wei.liu2@citrix.com>

And I have some nit-picking below.

> +
> +/* Set the RTDS scheduling parameters of vcpu(s) */
> +static int sched_rtds_vcpus_params_set(libxl__gc *gc, uint32_t domid,
> +                                       const libxl_vcpu_sched_params *scinfo)
> +{
> +    int r, rc;
> +    int i;
> +    uint16_t max_vcpuid;
> +    xc_dominfo_t info;
> +    struct xen_domctl_schedparam_vcpu *vcpus;
> +
> +    r = xc_domain_getinfo(CTX->xch, domid, 1, &info);
> +    if (r < 0) {
> +        LOGE(ERROR, "getting domain info");
> +        rc = ERROR_FAIL;
> +        goto out;
> +    }
> +    max_vcpuid = info.max_vcpu_id;
> +
> +    if (scinfo->num_vcpus <= 0) {
> +        rc = ERROR_INVAL;
> +        goto out;
> +    } else {
> +        for (i = 0; i < scinfo->num_vcpus; i++) {
> +            if (scinfo->vcpus[i].vcpuid < 0 ||
> +                scinfo->vcpus[i].vcpuid > max_vcpuid) {
> +                LOG(ERROR, "VCPU index is out of range, "
> +                           "valid values are within range from 0 to %d",
> +                           max_vcpuid);
> +                rc = ERROR_INVAL;
> +                goto out;
> +            }
> +            rc = sched_rtds_validate_params(gc, scinfo->vcpus[i].period,
> +                                            scinfo->vcpus[i].budget);
> +            if (rc) {
> +                rc = ERROR_INVAL;
> +                goto out;
> +            }
> +        }
> +        GCNEW_ARRAY(vcpus, scinfo->num_vcpus);
> +        for (i = 0; i < scinfo->num_vcpus; i++) {
> +            vcpus[i].vcpuid = scinfo->vcpus[i].vcpuid;
> +            vcpus[i].u.rtds.period = scinfo->vcpus[i].period;
> +            vcpus[i].u.rtds.budget = scinfo->vcpus[i].budget;
> +        }
> +    }
> +


You could have written this hunk like this:


    if (scinfo->num_vcpus <= 0) {
        rc = ERROR_INVAL;
        goto out;
    }

    for (i = 0; i < scinfo->num_vcpus; i++) {
        if (scinfo->vcpus[i].vcpuid < 0 ||
            scinfo->vcpus[i].vcpuid > max_vcpuid) {
            LOG(ERROR, "VCPU index is out of range, "
                       "valid values are within range from 0 to %d",
                       max_vcpuid);
            rc = ERROR_INVAL;
            goto out;
        }
        rc = sched_rtds_validate_params(gc, scinfo->vcpus[i].period,
                                        scinfo->vcpus[i].budget);
        if (rc) {
            rc = ERROR_INVAL;
            goto out;
        }
    }
    GCNEW_ARRAY(vcpus, scinfo->num_vcpus);
    for (i = 0; i < scinfo->num_vcpus; i++) {
        vcpus[i].vcpuid = scinfo->vcpus[i].vcpuid;
        vcpus[i].u.rtds.period = scinfo->vcpus[i].period;
        vcpus[i].u.rtds.budget = scinfo->vcpus[i].budget;
    }


But, you original code is still OK. This is just FYI. No need to resend
just because of this.

> +    r = xc_sched_rtds_vcpu_set(CTX->xch, domid,
> +                               vcpus, scinfo->num_vcpus);
> +    if (r != 0) {
> +        LOGE(ERROR, "setting vcpu sched rtds");
> +        rc = ERROR_FAIL;
> +        goto out;
> +    }
> +    rc = 0;
> +out:
> +    return rc;
> +}
> +
> +/* Set the RTDS scheduling parameters of all vcpus of a domain */
> +static int sched_rtds_vcpus_params_set_all(libxl__gc *gc, uint32_t domid,
> +                               const libxl_vcpu_sched_params *scinfo)
> +{
> +    int r, rc;
> +    int i;
> +    uint16_t max_vcpuid;
> +    xc_dominfo_t info;
> +    struct xen_domctl_schedparam_vcpu *vcpus;
> +    uint32_t num_vcpus;
> +
> +    r = xc_domain_getinfo(CTX->xch, domid, 1, &info);
> +    if (r < 0) {
> +        LOGE(ERROR, "getting domain info");
> +        rc = ERROR_FAIL;
> +        goto out;
> +    }
> +    max_vcpuid = info.max_vcpu_id;
> +
> +    if (scinfo->num_vcpus != 1) {
> +        rc = ERROR_INVAL;
> +        goto out;
> +    } else {
> +        if (sched_rtds_validate_params(gc, scinfo->vcpus[0].period,
> +                                       scinfo->vcpus[0].budget)) {
> +            rc = ERROR_INVAL;
> +            goto out;
> +        }
> +        num_vcpus = max_vcpuid + 1;
> +        GCNEW_ARRAY(vcpus, num_vcpus);
> +        for (i = 0; i < num_vcpus; i++) {
> +            vcpus[i].vcpuid = i;
> +            vcpus[i].u.rtds.period = scinfo->vcpus[0].period;
> +            vcpus[i].u.rtds.budget = scinfo->vcpus[0].budget;
> +        }
> +    }

Same here, the else branch can be simplified. Again, it's just FYI. No
need to resend.


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