mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-26 10:05:18 +07:00
4dc2375c1a
Rik reports that he sees an increase in CPU use in one benchmark due to commit 612f1a22f067 "cpuidle: poll_state: Add time limit to poll_idle()" that caused poll_idle() to call local_clock() in every iteration of the loop. Utilization increase generally means more non-idle time with respect to total CPU time (on the average) which implies reduced CPU frequency. Doug reports that limiting the rate of local_clock() invocations in there causes much less power to be drawn during a CPU-intensive parallel workload (with idle states 1 and 2 disabled to enforce more state 0 residency). These two reports together suggest that executing local_clock() on multiple CPUs in parallel at a high rate may cause chips to get hot and trigger thermal/power limits on them to kick in, so reduce the rate of local_clock() invocations in poll_idle() to avoid that issue. Fixes: 612f1a22f067 "cpuidle: poll_state: Add time limit to poll_idle()" Reported-by: Rik van Riel <riel@surriel.com> Reported-by: Doug Smythies <dsmythies@telus.net> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Tested-by: Rik van Riel <riel@surriel.com> Reviewed-by: Rik van Riel <riel@surriel.com>
53 lines
1.2 KiB
C
53 lines
1.2 KiB
C
/*
|
|
* poll_state.c - Polling idle state
|
|
*
|
|
* This file is released under the GPLv2.
|
|
*/
|
|
|
|
#include <linux/cpuidle.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/sched/clock.h>
|
|
#include <linux/sched/idle.h>
|
|
|
|
#define POLL_IDLE_TIME_LIMIT (TICK_NSEC / 16)
|
|
#define POLL_IDLE_RELAX_COUNT 200
|
|
|
|
static int __cpuidle poll_idle(struct cpuidle_device *dev,
|
|
struct cpuidle_driver *drv, int index)
|
|
{
|
|
u64 time_start = local_clock();
|
|
|
|
local_irq_enable();
|
|
if (!current_set_polling_and_test()) {
|
|
unsigned int loop_count = 0;
|
|
|
|
while (!need_resched()) {
|
|
cpu_relax();
|
|
if (loop_count++ < POLL_IDLE_RELAX_COUNT)
|
|
continue;
|
|
|
|
loop_count = 0;
|
|
if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT)
|
|
break;
|
|
}
|
|
}
|
|
current_clr_polling();
|
|
|
|
return index;
|
|
}
|
|
|
|
void cpuidle_poll_state_init(struct cpuidle_driver *drv)
|
|
{
|
|
struct cpuidle_state *state = &drv->states[0];
|
|
|
|
snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
|
|
snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
|
|
state->exit_latency = 0;
|
|
state->target_residency = 0;
|
|
state->power_usage = -1;
|
|
state->enter = poll_idle;
|
|
state->disabled = false;
|
|
state->flags = CPUIDLE_FLAG_POLLING;
|
|
}
|
|
EXPORT_SYMBOL_GPL(cpuidle_poll_state_init);
|