sched: framework for sched_mc/smt_power_savings=N (afb8a9b7) · Commits · 戴 / test

Impact: extend range of /sys/devices/system/cpu/sched_mc_power_savings Currently the sched_mc/smt_power_savings variable is a boolean, which either enables or disables topology based power savings. This patch extends the behaviour of the variable from boolean to multivalued, such that based on the value, we decide how aggressively do we want to perform powersavings balance at appropriate sched domain based on topology. Variable levels of power saving tunable would benefit end user to match the required level of power savings vs performance trade-off depending on the system configuration and workloads. This version makes the sched_mc_power_savings global variable to take more values (0,1,2). Later versions can have a single tunable called sched_power_savings instead of sched_{mc,smt}_power_savings. Signed-off-by:

Gautham R Shenoy <ego@in.ibm.com> Signed-off-by:

Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> Acked-by:

Balbir Singh <balbir@linux.vnet.ibm.com> Acked-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

include/linux/sched.h

+11 −0

Original line number	Diff line number	Diff line
		@@ -763,6 +763,17 @@ enum cpu_idle_type {
		#define SD_SERIALIZE 1024 /* Only a single load balancing instance */
		#define SD_WAKE_IDLE_FAR 2048 /* Gain latency sacrificing cache hit */

		enum powersavings_balance_level {
		POWERSAVINGS_BALANCE_NONE = 0, /* No power saving load balance */
		POWERSAVINGS_BALANCE_BASIC, /* Fill one thread/core/package
		* first for long running threads
		*/
		POWERSAVINGS_BALANCE_WAKEUP, /* Also bias task wakeups to semi-idle
		* cpu package for power savings
		*/
		MAX_POWERSAVINGS_BALANCE_LEVELS
		};

		extern int sched_mc_power_savings, sched_smt_power_savings;

		static inline int sd_balance_for_mc_power(void)

kernel/sched.c

+14 −3

Original line number	Diff line number	Diff line
		@@ -7906,14 +7906,25 @@ int arch_reinit_sched_domains(void)
		static ssize_t sched_power_savings_store(const char *buf, size_t count, int smt)
		{
		int ret;
		unsigned int level = 0;

		if (buf[0] != '0' && buf[0] != '1')
		if (sscanf(buf, "%u", &level) != 1)
		return -EINVAL;

		/*
		* level is always be positive so don't check for
		* level < POWERSAVINGS_BALANCE_NONE which is 0
		* What happens on 0 or 1 byte write,
		* need to check for count as well?
		*/

		if (level >= MAX_POWERSAVINGS_BALANCE_LEVELS)
		return -EINVAL;

		if (smt)
		sched_smt_power_savings = (buf[0] == '1');
		sched_smt_power_savings = level;
		else
		sched_mc_power_savings = (buf[0] == '1');
		sched_mc_power_savings = level;

		ret = arch_reinit_sched_domains();

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