5.4-stable review patch. If anyone has any objections, please let me know.
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From: Rafael J. Wysocki rafael.j.wysocki@intel.com
[ Upstream commit 85975daeaa4d6ec560bfcd354fc9c08ad7f38888 ]
When giving up on making a high-confidence prediction, get_typical_interval() always returns UINT_MAX which means that the next idle interval prediction will be based entirely on the time till the next timer. However, the information represented by the most recent intervals may not be completely useless in those cases.
Namely, the largest recent idle interval is an upper bound on the recently observed idle duration, so it is reasonable to assume that the next idle duration is unlikely to exceed it. Moreover, this is still true after eliminating the suspected outliers if the sample set still under consideration is at least as large as 50% of the maximum sample set size.
Accordingly, make get_typical_interval() return the current maximum recent interval value in that case instead of UINT_MAX.
Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reported-by: Artem Bityutskiy artem.bityutskiy@linux.intel.com Tested-by: Artem Bityutskiy artem.bityutskiy@linux.intel.com Reviewed-by: Christian Loehle christian.loehle@arm.com Tested-by: Christian Loehle christian.loehle@arm.com Tested-by: Aboorva Devarajan aboorvad@linux.ibm.com Link: https://patch.msgid.link/7770672.EvYhyI6sBW@rjwysocki.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/cpuidle/governors/menu.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index e5a5d0c8d66b1..bb7288f6adbf6 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -259,8 +259,19 @@ static unsigned int get_typical_interval(struct menu_device *data, * This can deal with workloads that have long pauses interspersed * with sporadic activity with a bunch of short pauses. */ - if ((divisor * 4) <= INTERVALS * 3) + if (divisor * 4 <= INTERVALS * 3) { + /* + * If there are sufficiently many data points still under + * consideration after the outliers have been eliminated, + * returning without a prediction would be a mistake because it + * is likely that the next interval will not exceed the current + * maximum, so return the latter in that case. + */ + if (divisor >= INTERVALS / 2) + return max; + return UINT_MAX; + }
thresh = max - 1; goto again;