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Subject[PATCH v3 16/24] thermal: intel: hfi: Define a default class for unclassified tasks
Date
A task may be unclassified if it has been recently created, spend most of
its lifetime sleeping, or hardware has not provided a classification.

Most tasks will be eventually classified as scheduler's IPC class 1
(HFI class 0). This class corresponds to the capabilities in the legacy,
classless, HFI table.

IPC class 1 is a reasonable choice until hardware provides an actual
classification. Meanwhile, the scheduler will place classes of tasks with
higher IPC scores on higher-performance CPUs.

Cc: Ben Segall <bsegall@google.com>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Lukasz Luba <lukasz.luba@arm.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tim C. Chen <tim.c.chen@intel.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: x86@kernel.org
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v2:
* None

Changes since v1:
* Now the default class is 1.
---
drivers/thermal/intel/intel_hfi.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/intel/intel_hfi.c b/drivers/thermal/intel/intel_hfi.c
index fa9b4a678d92..7ea6acce7107 100644
--- a/drivers/thermal/intel/intel_hfi.c
+++ b/drivers/thermal/intel/intel_hfi.c
@@ -185,6 +185,19 @@ static struct workqueue_struct *hfi_updates_wq;
#ifdef CONFIG_IPC_CLASSES
static int __percpu *hfi_ipcc_scores;

+/*
+ * A task may be unclassified if it has been recently created, spend most of
+ * its lifetime sleeping, or hardware has not provided a classification.
+ *
+ * Most tasks will be classified as scheduler's IPC class 1 (HFI class 0)
+ * eventually. Meanwhile, the scheduler will place classes of tasks with higher
+ * IPC scores on higher-performance CPUs.
+ *
+ * IPC class 1 is a reasonable choice. It matches the performance capability
+ * of the legacy, classless, HFI table.
+ */
+#define HFI_UNCLASSIFIED_DEFAULT 1
+
void intel_hfi_update_ipcc(struct task_struct *curr)
{
union hfi_thread_feedback_char_msr msr;
@@ -215,7 +228,7 @@ unsigned long intel_hfi_get_ipcc_score(unsigned short ipcc, int cpu)
return -EINVAL;

if (ipcc == IPC_CLASS_UNCLASSIFIED)
- return -EINVAL;
+ ipcc = HFI_UNCLASSIFIED_DEFAULT;

/*
* Scheduler IPC classes start at 1. HFI classes start at 0.
--
2.25.1
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