Re: [PATCH v4 1/7] libxl: get rid of the SEDF scheduler

[George Dunlap <george.dunlap@eu.citrix.com>]

On 07/07/2015 05:43 PM, Dario Faggioli wrote:
> only the interface is left in place, for backward
> compile-time compatibility, but every attempt to
> use it would throw an error.
> 
> Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
> ---
> Cc: George Dunlap <george.dunlap@eu.citrix.com>
> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> Cc: Ian Campbell <ian.campbell@citrix.com>
> Cc: Wei Liu <wei.liu2@citrix.com>

Acked-by: George Dunlap <george.dunlap@eu.citrix.com>

> 
> Changes from v3:
>  - drop George's Rev-by: which should not be there since v2;
>  - better grouping of fields in libxl_domain_sched_params, as
>    suggested during review;
>  - improved comment for ERROR_FEATURE_REMOVED, as suggested
>    during review.
> 
> Changes from v2:
>  - introduce and use ERROR_FEATURE_REMOVED, as requested
>    during review;
>  - mark the SEDF only parameter as deprecated in libxl_types.idl,
>    as requested during review.
> ---
>  tools/libxl/libxl.c         |   73 ++-----------------------------------------
>  tools/libxl/libxl_create.c  |   61 ------------------------------------
>  tools/libxl/libxl_types.idl |    8 ++++-
>  3 files changed, 11 insertions(+), 131 deletions(-)
> 
> diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> index 3a83903..38aff8d 100644
> --- a/tools/libxl/libxl.c
> +++ b/tools/libxl/libxl.c
> @@ -5728,73 +5728,6 @@ static int sched_credit2_domain_set(libxl__gc *gc, uint32_t domid,
>      return 0;
>  }
>  
> -static int sched_sedf_domain_get(libxl__gc *gc, uint32_t domid,
> -                                 libxl_domain_sched_params *scinfo)
> -{
> -    uint64_t period;
> -    uint64_t slice;
> -    uint64_t latency;
> -    uint16_t extratime;
> -    uint16_t weight;
> -    int rc;
> -
> -    rc = xc_sedf_domain_get(CTX->xch, domid, &period, &slice, &latency,
> -                            &extratime, &weight);
> -    if (rc != 0) {
> -        LOGE(ERROR, "getting domain sched sedf");
> -        return ERROR_FAIL;
> -    }
> -
> -    libxl_domain_sched_params_init(scinfo);
> -    scinfo->sched = LIBXL_SCHEDULER_SEDF;
> -    scinfo->period = period / 1000000;
> -    scinfo->slice = slice / 1000000;
> -    scinfo->latency = latency / 1000000;
> -    scinfo->extratime = extratime;
> -    scinfo->weight = weight;
> -
> -    return 0;
> -}
> -
> -static int sched_sedf_domain_set(libxl__gc *gc, uint32_t domid,
> -                                 const libxl_domain_sched_params *scinfo)
> -{
> -    uint64_t period;
> -    uint64_t slice;
> -    uint64_t latency;
> -    uint16_t extratime;
> -    uint16_t weight;
> -
> -    int ret;
> -
> -    ret = xc_sedf_domain_get(CTX->xch, domid, &period, &slice, &latency,
> -                            &extratime, &weight);
> -    if (ret != 0) {
> -        LOGE(ERROR, "getting domain sched sedf");
> -        return ERROR_FAIL;
> -    }
> -
> -    if (scinfo->period != LIBXL_DOMAIN_SCHED_PARAM_PERIOD_DEFAULT)
> -        period = (uint64_t)scinfo->period * 1000000;
> -    if (scinfo->slice != LIBXL_DOMAIN_SCHED_PARAM_SLICE_DEFAULT)
> -        slice = (uint64_t)scinfo->slice * 1000000;
> -    if (scinfo->latency != LIBXL_DOMAIN_SCHED_PARAM_LATENCY_DEFAULT)
> -        latency = (uint64_t)scinfo->latency * 1000000;
> -    if (scinfo->extratime != LIBXL_DOMAIN_SCHED_PARAM_EXTRATIME_DEFAULT)
> -        extratime = scinfo->extratime;
> -    if (scinfo->weight != LIBXL_DOMAIN_SCHED_PARAM_WEIGHT_DEFAULT)
> -        weight = scinfo->weight;
> -
> -    ret = xc_sedf_domain_set(CTX->xch, domid, period, slice, latency,
> -                            extratime, weight);
> -    if ( ret < 0 ) {
> -        LOGE(ERROR, "setting domain sched sedf");
> -        return ERROR_FAIL;
> -    }
> -
> -    return 0;
> -}
> -
>  static int sched_rtds_domain_get(libxl__gc *gc, uint32_t domid,
>                                 libxl_domain_sched_params *scinfo)
>  {
> @@ -5873,7 +5806,8 @@ int libxl_domain_sched_params_set(libxl_ctx *ctx, uint32_t domid,
>  
>      switch (sched) {
>      case LIBXL_SCHEDULER_SEDF:
> -        ret=sched_sedf_domain_set(gc, domid, scinfo);
> +        LOG(ERROR, "SEDF scheduler no longer available");
> +        ret=ERROR_FEATURE_REMOVED;
>          break;
>      case LIBXL_SCHEDULER_CREDIT:
>          ret=sched_credit_domain_set(gc, domid, scinfo);
> @@ -5909,7 +5843,8 @@ int libxl_domain_sched_params_get(libxl_ctx *ctx, uint32_t domid,
>  
>      switch (scinfo->sched) {
>      case LIBXL_SCHEDULER_SEDF:
> -        ret=sched_sedf_domain_get(gc, domid, scinfo);
> +        LOG(ERROR, "SEDF scheduler no longer available");
> +        ret=ERROR_FEATURE_REMOVED;
>          break;
>      case LIBXL_SCHEDULER_CREDIT:
>          ret=sched_credit_domain_get(gc, domid, scinfo);
> diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
> index 9c2303c..3f31a3b 100644
> --- a/tools/libxl/libxl_create.c
> +++ b/tools/libxl/libxl_create.c
> @@ -50,61 +50,6 @@ int libxl__domain_create_info_setdefault(libxl__gc *gc,
>      return 0;
>  }
>  
> -static int sched_params_valid(libxl__gc *gc,
> -                              uint32_t domid, libxl_domain_sched_params *scp)
> -{
> -    int has_weight = scp->weight != LIBXL_DOMAIN_SCHED_PARAM_WEIGHT_DEFAULT;
> -    int has_period = scp->period != LIBXL_DOMAIN_SCHED_PARAM_PERIOD_DEFAULT;
> -    int has_slice = scp->slice != LIBXL_DOMAIN_SCHED_PARAM_SLICE_DEFAULT;
> -    int has_extratime =
> -                scp->extratime != LIBXL_DOMAIN_SCHED_PARAM_EXTRATIME_DEFAULT;
> -
> -    /* The sedf scheduler needs some more consistency checking */
> -    if (libxl__domain_scheduler(gc, domid) == LIBXL_SCHEDULER_SEDF) {
> -        if (has_weight && (has_period || has_slice))
> -            return 0;
> -        /* If you want a real-time domain, with its own period and
> -         * slice, please, do provide both! */
> -        if (has_period != has_slice)
> -            return 0;
> -
> -        /*
> -         * Idea is, if we specify a weight, then both period and
> -         * slice has to be zero. OTOH, if we do specify a period and
> -         * slice, it is weight that should be zeroed. See
> -         * docs/misc/sedf_scheduler_mini-HOWTO.txt for more details
> -         * on the meaningful combinations and their meanings.
> -         */
> -        if (has_weight) {
> -            scp->slice = 0;
> -            scp->period = 0;
> -        }
> -        else if (!has_period) {
> -            /* No weight nor slice/period means best effort. Parameters needs
> -             * some mangling in order to properly ask for that, though. */
> -
> -            /*
> -             * Providing no weight does not make any sense if we do not allow
> -             * the domain to run in extra time. On the other hand, if we have
> -             * extra time, weight will be ignored (and zeroed) by Xen, but it
> -             * can't be zero here, or the call for setting the scheduling
> -             * parameters will fail. So, avoid the latter by setting a random
> -             * weight (namely, 1), as it will be ignored anyway.
> -             */
> -
> -            /* We can setup a proper best effort domain (extra time only)
> -             * iff we either already have or are asking for some extra time. */
> -            scp->weight = has_extratime ? scp->extratime : 1;
> -            scp->period = 0;
> -        } else {
> -            /* Real-time domain: will get slice CPU time over every period */
> -            scp->weight = 0;
> -        }
> -    }
> -
> -    return 1;
> -}
> -
>  int libxl__domain_build_info_setdefault(libxl__gc *gc,
>                                          libxl_domain_build_info *b_info)
>  {
> @@ -888,12 +833,6 @@ static void initiate_domain_create(libxl__egc *egc,
>      ret = libxl__domain_build_info_setdefault(gc, &d_config->b_info);
>      if (ret) goto error_out;
>  
> -    if (!sched_params_valid(gc, domid, &d_config->b_info.sched_params)) {
> -        LOG(ERROR, "Invalid scheduling parameters\n");
> -        ret = ERROR_INVAL;
> -        goto error_out;
> -    }
> -
>      for (i = 0; i < d_config->num_disks; i++) {
>          ret = libxl__device_disk_setdefault(gc, &d_config->disks[i]);
>          if (ret) goto error_out;
> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> index e1632fa..378d6e3 100644
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -68,6 +68,7 @@ libxl_error = Enumeration("error", [
>      (-22, "ABORTED"),
>      (-23, "NOTFOUND"),
>      (-24, "DOMAIN_DESTROYED"), # Target domain ceased to exist during op
> +    (-25, "FEATURE_REMOVED"), # For functionality that has been removed
>      ], value_namespace = "")
>  
>  libxl_domain_type = Enumeration("domain_type", [
> @@ -356,10 +357,15 @@ libxl_domain_sched_params = Struct("domain_sched_params",[
>      ("weight",       integer, {'init_val': 'LIBXL_DOMAIN_SCHED_PARAM_WEIGHT_DEFAULT'}),
>      ("cap",          integer, {'init_val': 'LIBXL_DOMAIN_SCHED_PARAM_CAP_DEFAULT'}),
>      ("period",       integer, {'init_val': 'LIBXL_DOMAIN_SCHED_PARAM_PERIOD_DEFAULT'}),
> +    ("budget",       integer, {'init_val': 'LIBXL_DOMAIN_SCHED_PARAM_BUDGET_DEFAULT'}),
> +
> +    # The following three parameters ('slice', 'latency' and 'extratime') are deprecated,
> +    # and will have no effect if used, since the SEDF scheduler has been removed.
> +    # Note that 'period' was an SDF parameter too, but it is still effective as it is
> +    # now used (together with 'budget') by the RTDS scheduler.
>      ("slice",        integer, {'init_val': 'LIBXL_DOMAIN_SCHED_PARAM_SLICE_DEFAULT'}),
>      ("latency",      integer, {'init_val': 'LIBXL_DOMAIN_SCHED_PARAM_LATENCY_DEFAULT'}),
>      ("extratime",    integer, {'init_val': 'LIBXL_DOMAIN_SCHED_PARAM_EXTRATIME_DEFAULT'}),
> -    ("budget",       integer, {'init_val': 'LIBXL_DOMAIN_SCHED_PARAM_BUDGET_DEFAULT'}),
>      ])
>  
>  libxl_vnode_info = Struct("vnode_info", [
>