linux-kernel - [PATCH v4 16/24] thermal: intel: hfi: Define a default class for unclassified tasks

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Message-Id: <20230613042422.5344-17-ricardo.neri-calderon@linux.intel.com>
Date:   Mon, 12 Jun 2023 21:24:14 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Ricardo Neri <ricardo.neri@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Lukasz Luba <lukasz.luba@....com>,
        Ionela Voinescu <ionela.voinescu@....com>,
        Zhao Liu <zhao1.liu@...el.com>,
        "Yuan, Perry" <Perry.Yuan@....com>, x86@...nel.org,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        "Tim C . Chen" <tim.c.chen@...el.com>,
        Zhao Liu <zhao1.liu@...ux.intel.com>
Subject: [PATCH v4 16/24] thermal: intel: hfi: Define a default class for unclassified tasks

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@...gle.com>
Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Ionela Voinescu <ionela.voinescu@....com>
Cc: Joel Fernandes (Google) <joel@...lfernandes.org>
Cc: Len Brown <len.brown@...el.com>
Cc: Lukasz Luba <lukasz.luba@....com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Perry Yuan <Perry.Yuan@....com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Tim C. Chen <tim.c.chen@...el.com>
Cc: Valentin Schneider <vschneid@...hat.com>
Cc: Zhao Liu <zhao1.liu@...ux.intel.com>
Cc: x86@...nel.org
Cc: linux-pm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
---
Changes since v3:
 * Added Acked-by tag from Rafael.

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 fec2c01fda1b..e23c49da02ee 100644
--- a/drivers/thermal/intel/intel_hfi.c
+++ b/drivers/thermal/intel/intel_hfi.c
@@ -182,6 +182,19 @@ static struct workqueue_struct *hfi_updates_wq;
 #define HFI_UPDATE_INTERVAL		HZ
 #define HFI_MAX_THERM_NOTIFY_COUNT	16
 
+/*
+ * 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
+
 /* A cache of the HFI perf capabilities for lockless access. */
 static int __percpu *hfi_ipcc_scores;
 /* Sequence counter for hfi_ipcc_scores */
@@ -212,7 +225,7 @@ 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