[Xen-devel] Re: bvt scheduler has two bugs?

["Satoshi Uchida" <s-uchida@xxxxxxxxxxxxx>]

Hi.

In BVT scheduler setup, location of bug is determined.
If new guest domain is created by xm create command,
warpl and warpu parameters multiples MILLISECS * MULLISECS.

In  tools/libxc/xc_domain.c,

    op.cmd = DOM0_CREATEDOMAIN;
    op.u.createdomain.domain = (domid_t)*pdomid;
    op.u.createdomain.memory_kb = mem_kb;
    op.u.createdomain.cpu = cpu;

    if ( (err = do_dom0_op(xc_handle, &op)) == 0 )   <<< (1)
    {
        *pdomid = (u16)op.u.createdomain.domain;

         err = xc_domain_setcpuweight(xc_handle, *pdomid, cpu_weight); <<< 
(2)
    }

This algorithm is default value * MILLISECS at add_task function
in xen/common/sched_bvt.c via do_dom0_op function (1).
If a creation of new domain is success, it's parameters are setting
adjdom function in xen/common/sched_bvt.c via xc_domain_setcpuweight
function (2).
So that, below two parameter become default values *  MILLISECS * 
MILLISECS.

However, In xm bvt command, only adjdom function is called at once.
Therefore, BVT parameter setting is different to your intention.

I can not judge that error is in xm create command or in xm bvt command.
If former is, you needs to modified as follow.

  Insert "#include <xen/time.h>"  in  tools/libxc/xc_domain.c, and
  in tools/libxc/xc_domain.c - xc_domain_setcpuweight : line 200


        case SCHED_BVT:
        {
            u32 mcuadv;
            int warpback;
            s32 warpvalue;
            long long warpl;
            long long warpu;

            /* Preserve all the scheduling parameters apart
               of MCU advance. */
            if((ret = xc_bvtsched_domain_get(xc_handle, domid, &mcuadv,
                                &warpback, &warpvalue, &warpl, &warpu)))
                return ret;

            /* The MCU advance is inverse of the weight.
               Default value of the weight is 1, default mcuadv 10.
               The scaling factor is therefore 10. */
            if(weight > 0) mcuadv = 10 / weight;

       +   warpl /= MILLISECS(1)
       +   warpu /= MILLISECS(1)

            ret = xc_bvtsched_domain_set(xc_handle, domid, mcuadv,
                                         warpback, warpvalue, warpl, 
warpu);
            break;
        }


If latter,

  in xen/common/sched_bvt.c - bvt_adjdom function : line 318

        inf->warpl = MILLISECS(warpl);     >>   inf->warpl = warpl;
        inf->warpu = MILLISECS(warpu);   >>   inf->warpu = warpu;

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