Re: [Xen-devel] [PATCH v3 for Xen 4.6 2/4] libxc: enable per-VCPU parameter settings for RTDS scheduler

[Chong Li <lichong659@xxxxxxxxx>]

On Tue, Jun 30, 2015 at 10:32 AM, Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
> On Tue, 2015-06-30 at 10:18 -0500, Chong Li wrote:
>> On Tue, Jun 30, 2015 at 7:22 AM, Ian Campbell <ian.campbell@xxxxxxxxxx> 
>> wrote:
>> > On Sun, 2015-06-28 at 21:44 -0500, Chong Li wrote:
>> >
>> >> diff --git a/tools/libxc/xc_csched.c b/tools/libxc/xc_csched.c
>> >> index 390c645..5a2bdf4 100644
>> >> --- a/tools/libxc/xc_csched.c
>> >> +++ b/tools/libxc/xc_csched.c
>> >> @@ -36,7 +36,7 @@ xc_sched_credit_domain_set(
>> >>      domctl.domain = (domid_t) domid;
>> >>      domctl.u.scheduler_op.sched_id = XEN_SCHEDULER_CREDIT;
>> >>      domctl.u.scheduler_op.cmd = XEN_DOMCTL_SCHEDOP_putinfo;
>> >> -    domctl.u.scheduler_op.u.credit = *sdom;
>> >> +    domctl.u.scheduler_op.u.d.credit = *sdom;
>> >
>> > I don't see any change to any types in this series, which makes me
>> > suspect it is in another patch and that bisectability is therefore not
>> > maintained through the series. Each patch in the series needs to build
>> > when they are applied one by one.
>> >
>> > This probably means that at to at least some degree hypercall interface
>> > changes need to be done in the same time as the libxc adjustments. You
>> > can still keep the _new_ functionality in a separate patch of course (if
>> > that makes sense in this case).
>>
>> Because both per-domain and per-vcpu parameters are now unioned in
>> struct xen_domctl_scheduler_op, we need to specify per-domain or
>> per-vcpu when using domctl.u.scheduler_op.u (.d means per-domain, .v
>> means per-vcpu). This change also happens to the XEN_DOMCTL_SCHEDOP_*
>> handlers (of all schedulers), where the domctl.u.scheduler_op.u.* is
>> passed to.
>
> I understand the interface change, but the problem is that the interface
> change and the change ot the users of that interface seem to be in
> different patches, which breaks bisectability.
>
> Does this series compile and work at every step?
>
> i.e. the following combinations of patches from this 4 patch series all
> need to build and work successfully:
>
> Patch #1
> Patch #1+#2
> Patch #1+#2+#3
> Patch #1+#2+#3+#4
>
> Is that the case?

I see your point. Do you mean the change of struct
xen_domctl_scheduler_op, the change of XEN_DOMCTL_SCHEDOP_* handlers
(in xen) and the change of libxc (just shown above) should be in the
same patch? Should the title of that patch be something like
"xen+libxc: enable per-vcpu parameter settings for RTDS scheduler" ?

Chong
>
> Ian.
>



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

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