From:   Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To:     "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>
Cc:     Ricardo Neri <ricardo.neri@intel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Ben Segall <bsegall@google.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Len Brown <len.brown@intel.com>, Mel Gorman <mgorman@suse.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Valentin Schneider <vschneid@redhat.com>,
        Lukasz Luba <lukasz.luba@arm.com>,
        Ionela Voinescu <ionela.voinescu@arm.com>, x86@kernel.org,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        Ricardo Neri <ricardo.neri-calderon@linux.intel.com>,
        "Tim C . Chen" <tim.c.chen@intel.com>
Subject: [PATCH v3 16/24] thermal: intel: hfi: Define a default class for unclassified tasks
Date:   Mon,  6 Feb 2023 21:10:57 -0800
Message-Id: <20230207051105.11575-17-ricardo.neri-calderon@linux.intel.com>
In-Reply-To: <20230207051105.11575-1-ricardo.neri-calderon@linux.intel.com>
References: <20230207051105.11575-1-ricardo.neri-calderon@linux.intel.com>
Precedence: bulk

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