From: Juergen Gross <jgross@suse.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: Tim Deegan <tim@xen.org>,
Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
George Dunlap <george.dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>,
Robert VanVossen <robert.vanvossen@dornerworks.com>,
Dario Faggioli <dfaggioli@suse.com>,
Julien Grall <julien.grall@arm.com>,
Josh Whitehead <josh.whitehead@dornerworks.com>,
Meng Xu <mengxu@cis.upenn.edu>,
xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [PATCH v2 21/48] xen/sched: use sched_resource cpu instead smp_processor_id in schedulers
Date: Thu, 12 Sep 2019 11:34:23 +0200 [thread overview]
Message-ID: <13f2cf63-2b61-07fa-f43d-044c61601bca@suse.com> (raw)
In-Reply-To: <18ec96a1-b3c3-adbf-4b0e-1fcb7185e046@suse.com>
On 09.09.19 16:17, Jan Beulich wrote:
> On 09.08.2019 16:58, Juergen Gross wrote:
>> Especially in the do_schedule() functions of the different schedulers
>> using smp_processor_id() for the local cpu number is correct only if
>> the sched_unit is a single vcpu. As soon as larger sched_units are
>> used most uses should be replaced by the cpu number of the local
>> sched_resource instead.
>
> I have to admit that I don't follow this argument, not the least because
> (as I think I had indicated before) it is unclear to me what _the_ (i.e.
> single) CPU for a sched unit is. I've gone back to patches 4 and 7
> without finding what the conceptual model behind this is intended to be.
> Besides an explanation I think one or both of those two patches also
> want to be revisited wrt the use of the name "processor" for the
> respective field.
Fair point. Naming it "master_cpu" in struct sched_resource and when
referencing it seems to be a good idea.
>
>> --- a/xen/common/sched_credit.c
>> +++ b/xen/common/sched_credit.c
>> @@ -1684,7 +1684,7 @@ csched_load_balance(struct csched_private *prv, int cpu,
>> int peer_cpu, first_cpu, peer_node, bstep;
>> int node = cpu_to_node(cpu);
>>
>> - BUG_ON( cpu != sched_unit_cpu(snext->unit) );
>> + BUG_ON( sched_get_resource_cpu(cpu) != sched_unit_cpu(snext->unit) );
>
> In cases like this one, would you mind dropping the stray blanks
> immediately inside the parentheses?
Will do.
>
>> @@ -1825,8 +1825,9 @@ static struct task_slice
>> csched_schedule(
>> const struct scheduler *ops, s_time_t now, bool_t tasklet_work_scheduled)
>> {
>> - const int cpu = smp_processor_id();
>> - struct list_head * const runq = RUNQ(cpu);
>> + const unsigned int cpu = smp_processor_id();
>> + const unsigned int sched_cpu = sched_get_resource_cpu(cpu);
>> + struct list_head * const runq = RUNQ(sched_cpu);
>
> By retaining a local variable named "cpu" you make it close to
> impossible to notice, during a re-base, an addition to the
> function still referencing a variable of this name. Similarly
> review is being made harder because one needs to go hunt all
> the remaining uses of "cpu". For example there a trace entry
> being generated, and it's not obvious to me whether this wouldn't
> better also used sched_cpu.
Okayy, I'll rename "cpu" to "my_cpu".
I used cpu in the trace entry on purpose, as it might be interesting on
which cpu the entry has been produced.
>
>> @@ -1967,7 +1968,7 @@ csched_schedule(
>> if ( snext->pri > CSCHED_PRI_TS_OVER )
>> __runq_remove(snext);
>> else
>> - snext = csched_load_balance(prv, cpu, snext, &ret.migrated);
>> + snext = csched_load_balance(prv, sched_cpu, snext, &ret.migrated);
>
> And in a case like this one I wonder whether passing a "sort of
> CPU" isn't sufficiently confusing, compared to e.g. simply
> passing the corresponding unit.
I guess you mean sched_resource.
I don't think changing the parameter type is a good idea. We need both
(resource and cpu number) on caller and callee side, but the main
object csched_load_balance() is working on is the cpu number.
>
>> @@ -1975,12 +1976,12 @@ csched_schedule(
>> */
>> if ( !tasklet_work_scheduled && snext->pri == CSCHED_PRI_IDLE )
>> {
>> - if ( !cpumask_test_cpu(cpu, prv->idlers) )
>> - cpumask_set_cpu(cpu, prv->idlers);
>> + if ( !cpumask_test_cpu(sched_cpu, prv->idlers) )
>> + cpumask_set_cpu(sched_cpu, prv->idlers);
>> }
>> - else if ( cpumask_test_cpu(cpu, prv->idlers) )
>> + else if ( cpumask_test_cpu(sched_cpu, prv->idlers) )
>> {
>> - cpumask_clear_cpu(cpu, prv->idlers);
>> + cpumask_clear_cpu(sched_cpu, prv->idlers);
>> }
>
> And this looks to be a pretty gross abuse of CPU masks then.
> (Nevertheless I can see that using a CPU as a vehicle here is
> helpful to limit the scope of the already long series, but I
> think it needs to be made much more apparent what is meant.)
I don't think it is an abuse. Think of it as a cpumask where only
the bits related to the resource's master_cpus can be set.
>
>> --- a/xen/common/schedule.c
>> +++ b/xen/common/schedule.c
>> @@ -112,7 +112,7 @@ static struct task_slice sched_idle_schedule(
>> const unsigned int cpu = smp_processor_id();
>> struct task_slice ret = { .time = -1 };
>>
>> - ret.task = sched_idle_unit(cpu);
>> + ret.task = sched_idle_unit(sched_get_resource_cpu(cpu));
>
> Shouldn't sched_idle_unit(cpu) == sched_idle_unit(sched_get_resource_cpu(cpu))
> here?
Yes.
Juergen
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next prev parent reply other threads:[~2019-09-12 9:35 UTC|newest]
Thread overview: 126+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-09 14:57 [Xen-devel] [PATCH v2 00/48] xen: add core scheduling support Juergen Gross
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 01/48] xen/sched: use new sched_unit instead of vcpu in scheduler interfaces Juergen Gross
2019-09-02 9:07 ` Jan Beulich
2019-09-09 5:26 ` Juergen Gross
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 02/48] xen/sched: move per-vcpu scheduler private data pointer to sched_unit Juergen Gross
2019-08-23 10:47 ` Dario Faggioli
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 03/48] xen/sched: build a linked list of struct sched_unit Juergen Gross
2019-08-23 10:52 ` Dario Faggioli
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 04/48] xen/sched: introduce struct sched_resource Juergen Gross
2019-08-23 10:54 ` Dario Faggioli
2019-09-04 13:10 ` Jan Beulich
2019-09-09 5:31 ` Juergen Gross
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 05/48] xen/sched: let pick_cpu return a scheduler resource Juergen Gross
2019-09-04 13:34 ` Jan Beulich
2019-09-09 5:43 ` Juergen Gross
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 06/48] xen/sched: switch schedule_data.curr to point at sched_unit Juergen Gross
2019-09-04 13:36 ` Jan Beulich
2019-09-09 5:46 ` Juergen Gross
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 07/48] xen/sched: move per cpu scheduler private data into struct sched_resource Juergen Gross
2019-09-04 13:48 ` Jan Beulich
2019-09-05 7:13 ` Juergen Gross
2019-09-05 7:38 ` Jan Beulich
2019-09-09 13:03 ` Dario Faggioli
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 08/48] xen/sched: switch vcpu_schedule_lock to unit_schedule_lock Juergen Gross
2019-09-04 14:02 ` Jan Beulich
2019-09-04 14:41 ` Juergen Gross
2019-09-04 14:54 ` Jan Beulich
2019-09-04 15:02 ` Juergen Gross
2019-09-11 16:02 ` Dario Faggioli
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 09/48] xen/sched: move some per-vcpu items to struct sched_unit Juergen Gross
2019-09-04 14:16 ` Jan Beulich
2019-09-09 6:39 ` Juergen Gross
2019-09-09 6:55 ` Jan Beulich
2019-09-09 7:05 ` Juergen Gross
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 10/48] xen/sched: add scheduler helpers hiding vcpu Juergen Gross
2019-09-04 14:49 ` Jan Beulich
2019-09-11 13:22 ` Juergen Gross
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 11/48] xen/sched: rename scheduler related perf counters Juergen Gross
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 12/48] xen/sched: switch struct task_slice from vcpu to sched_unit Juergen Gross
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 13/48] xen/sched: add is_running indicator to struct sched_unit Juergen Gross
2019-09-04 15:06 ` Jan Beulich
2019-09-11 13:44 ` Juergen Gross
2019-09-11 15:06 ` Jan Beulich
2019-09-11 15:32 ` Juergen Gross
2019-08-09 14:57 ` [Xen-devel] [PATCH v2 14/48] xen/sched: make null scheduler vcpu agnostic Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 15/48] xen/sched: make rt " Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 16/48] xen/sched: make credit " Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 17/48] xen/sched: make credit2 " Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 18/48] xen/sched: make arinc653 " Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 19/48] xen: add sched_unit_pause_nosync() and sched_unit_unpause() Juergen Gross
2019-09-09 13:34 ` Jan Beulich
2019-09-11 14:15 ` Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 20/48] xen: let vcpu_create() select processor Juergen Gross
2019-08-23 16:42 ` Julien Grall
2019-09-09 13:38 ` Jan Beulich
2019-09-11 14:22 ` Juergen Gross
2019-09-11 17:20 ` Dario Faggioli
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 21/48] xen/sched: use sched_resource cpu instead smp_processor_id in schedulers Juergen Gross
2019-09-09 14:17 ` Jan Beulich
2019-09-12 9:34 ` Juergen Gross [this message]
2019-09-12 10:04 ` Jan Beulich
2019-09-12 11:03 ` Juergen Gross
2019-09-12 11:17 ` Juergen Gross
2019-09-12 11:46 ` Jan Beulich
2019-09-12 11:53 ` Juergen Gross
2019-09-12 12:08 ` Jan Beulich
2019-09-12 12:13 ` Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 22/48] xen/sched: switch schedule() from vcpus to sched_units Juergen Gross
2019-09-09 14:35 ` Jan Beulich
2019-09-12 13:44 ` Juergen Gross
2019-09-12 14:34 ` Jan Beulich
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 23/48] xen/sched: switch sched_move_irqs() to take sched_unit as parameter Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 24/48] xen: switch from for_each_vcpu() to for_each_sched_unit() Juergen Gross
2019-09-09 15:14 ` Jan Beulich
2019-09-12 14:02 ` Juergen Gross
2019-09-12 14:40 ` Jan Beulich
2019-09-12 14:47 ` Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 25/48] xen/sched: add runstate counters to struct sched_unit Juergen Gross
2019-09-09 14:30 ` Jan Beulich
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 26/48] xen/sched: rework and rename vcpu_force_reschedule() Juergen Gross
2019-09-10 14:06 ` Jan Beulich
2019-09-13 9:33 ` Juergen Gross
2019-09-13 9:40 ` Jan Beulich
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 27/48] xen/sched: Change vcpu_migrate_*() to operate on schedule unit Juergen Gross
2019-09-10 15:11 ` Jan Beulich
2019-09-13 12:33 ` Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 28/48] xen/sched: move struct task_slice into struct sched_unit Juergen Gross
2019-09-10 15:18 ` Jan Beulich
2019-09-13 12:56 ` Juergen Gross
2019-09-12 8:13 ` Dario Faggioli
2019-09-12 8:21 ` Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 29/48] xen/sched: add code to sync scheduling of all vcpus of a sched unit Juergen Gross
2019-09-10 15:36 ` Jan Beulich
2019-09-13 13:12 ` Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 30/48] xen/sched: introduce unit_runnable_state() Juergen Gross
2019-09-11 10:30 ` Jan Beulich
2019-09-12 10:22 ` Dario Faggioli
2019-09-13 14:07 ` Juergen Gross
2019-09-13 14:44 ` Jan Beulich
2019-09-13 15:23 ` Juergen Gross
2019-09-12 10:24 ` Dario Faggioli
2019-09-13 14:14 ` Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 31/48] xen/sched: add support for multiple vcpus per sched unit where missing Juergen Gross
2019-09-11 10:43 ` Jan Beulich
2019-09-13 15:01 ` Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 32/48] xen/sched: modify cpupool_domain_cpumask() to be an unit mask Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 33/48] xen/sched: support allocating multiple vcpus into one sched unit Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 34/48] xen/sched: add a percpu resource index Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 35/48] xen/sched: add fall back to idle vcpu when scheduling unit Juergen Gross
2019-09-11 11:33 ` Julien Grall
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 36/48] xen/sched: make vcpu_wake() and vcpu_sleep() core scheduling aware Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 37/48] xen/sched: carve out freeing sched_unit memory into dedicated function Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 38/48] xen/sched: move per-cpu variable scheduler to struct sched_resource Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 39/48] xen/sched: move per-cpu variable cpupool " Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 40/48] xen/sched: reject switching smt on/off with core scheduling active Juergen Gross
2019-09-10 15:47 ` Jan Beulich
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 41/48] xen/sched: prepare per-cpupool scheduling granularity Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 42/48] xen/sched: split schedule_cpu_switch() Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 43/48] xen/sched: protect scheduling resource via rcu Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 44/48] xen/sched: support multiple cpus per scheduling resource Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 45/48] xen/sched: support differing granularity in schedule_cpu_[add/rm]() Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 46/48] xen/sched: support core scheduling for moving cpus to/from cpupools Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 47/48] xen/sched: disable scheduling when entering ACPI deep sleep states Juergen Gross
2019-08-09 14:58 ` [Xen-devel] [PATCH v2 48/48] xen/sched: add scheduling granularity enum Juergen Gross
2019-08-15 10:17 ` [Xen-devel] [PATCH v2 00/48] xen: add core scheduling support Sergey Dyasli
2019-09-05 6:22 ` Juergen Gross
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