On Monday, November 6, 2017 6:47:35 PM CET Reinette Chatre wrote: > Hi Rafael, > > On 11/4/2017 5:34 AM, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > > > The special value of 0 for device resume latency PM QoS means > > "no restriction", but there are two problems with that. > > > > First, device resume latency PM QoS requests with 0 as the > > value are always put in front of requests with positive > > values in the priority lists used internally by the PM QoS > > framework, causing 0 to be chosen as an effective constraint > > value. However, that 0 is then interpreted as "no restriction" > > effectively overriding the other requests with specific > > restrictions which is incorrect. > > > > Second, the users of device resume latency PM QoS have no > > way to specify that *any* resume latency at all should be > > avoided, which is an artificial limitation in general. > > > > To address these issues, modify device resume latency PM QoS to > > use S32_MAX as the "no constraint" value and 0 as the "no > > latency at all" one and rework its users (the cpuidle menu > > governor, the genpd QoS governor and the runtime PM framework) > > to follow these changes. > > > > Also add a special "n/a" value to the corresponding user space I/F > > to allow user space to indicate that it cannot accept any resume > > latencies at all for the given device. > > > > Fixes: 85dc0b8a4019 (PM / QoS: Make it possible to expose PM QoS latency > > constraints) > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=197323 > > Reported-by: Reinette Chatre <reinette.cha...@intel.com> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > Acked-by: Ramesh Thomas <ramesh.tho...@intel.com> > > --- > > > > Re-sending as an update rather than as v3, because the update is very minor > > (an additional check under the WARN_ON() in apply_constraint()). > > > > Reinette, please test this one instead of the last version. The WARN_ON() > > issue should be gone with this. > > > > I tested this update of the v2 2/2 patch with v2 of 1/2 but please note as > captured below that I am testing with the menu governor, so not testing 1/2 > if I understand correctly. > > I just repeated the test I ran against the original patch that was merged, > with some details added. I hope that it has some value to you considering > that it did not catch all issues the first time :( > > I tested on an Intel(R) NUC NUC6CAYS (Apollo Lake with a Goldmont cpu). As > you maybe know it has some issues with monitor/mwait, so acpi_idle is used: > # grep . /sys/devices/system/cpu/cpuidle/current_* > /sys/devices/system/cpu/cpuidle/current_driver:acpi_idle > /sys/devices/system/cpu/cpuidle/current_governor_ro:menu > > As with your original patch I still see the new behavior on boot: > swapper/0-1 [000] .... 0.347284: dev_pm_qos_add_request: > device=cpu0 type=DEV_PM_QOS_RESUME_LATENCY new_value=2147483647 > swapper/0-1 [000] .... 0.347300: pm_qos_update_target: > action=ADD_REQ prev_value=2147483647 curr_value=2147483647 > swapper/0-1 [000] .... 0.347533: dev_pm_qos_add_request: > device=cpu1 type=DEV_PM_QOS_RESUME_LATENCY new_value=2147483647 > swapper/0-1 [000] .... 0.347536: pm_qos_update_target: > action=ADD_REQ prev_value=2147483647 curr_value=2147483647 > swapper/0-1 [000] .... 0.347741: dev_pm_qos_add_request: > device=cpu2 type=DEV_PM_QOS_RESUME_LATENCY new_value=2147483647 > swapper/0-1 [000] .... 0.347743: pm_qos_update_target: > action=ADD_REQ prev_value=2147483647 curr_value=2147483647 > swapper/0-1 [000] .... 0.347958: dev_pm_qos_add_request: > device=cpu3 type=DEV_PM_QOS_RESUME_LATENCY new_value=2147483647 > swapper/0-1 [000] .... 0.347961: pm_qos_update_target: > action=ADD_REQ prev_value=2147483647 curr_value=2147483647 > > Even though the default latency required values on boot are much higher, the > user API still shows zero: > # grep . /sys/devices/system/cpu/cpu?/power/pm_qos_resume_latency_us > /sys/devices/system/cpu/cpu0/power/pm_qos_resume_latency_us:0 > /sys/devices/system/cpu/cpu1/power/pm_qos_resume_latency_us:0 > /sys/devices/system/cpu/cpu2/power/pm_qos_resume_latency_us:0 > /sys/devices/system/cpu/cpu3/power/pm_qos_resume_latency_us:0 > > At this time when I run turbostat I observe that more than 99% of time is > spent in C6 as reported by the actual hardware counters (the CPU%c6 value). I > also see that the requested value is more than 99% for C3. > > In my code the dev_pm_qos_add_request() API is used to request a new latency > requirement of 30 usec (this previously failed) from core #2 and #3. I run my > code with tracing enabled while also running turbostat. Tracing now shows me > a successful request: > > runit-505 [003] .... 393.656679: dev_pm_qos_add_request: > device=cpu2 type=DEV_PM_QOS_RESUME_LATENCY new_value=30 > runit-505 [003] .... 393.656700: pm_qos_update_target: > action=ADD_REQ prev_value=2147483647 curr_value=30 > runit-505 [003] .... 393.656705: dev_pm_qos_add_request: > device=cpu3 type=DEV_PM_QOS_RESUME_LATENCY new_value=30 > runit-505 [003] .... 393.656707: pm_qos_update_target: > action=ADD_REQ prev_value=2147483647 curr_value=30 > > Turbostat also reflects this with cores 2 and 3 now reporting more than 99% > in their CPU%c1 and C1% columns. > > User API still shows: > # grep . /sys/devices/system/cpu/cpu?/power/pm_qos_resume_latency_us > /sys/devices/system/cpu/cpu0/power/pm_qos_resume_latency_us:0 > /sys/devices/system/cpu/cpu1/power/pm_qos_resume_latency_us:0 > /sys/devices/system/cpu/cpu2/power/pm_qos_resume_latency_us:0 > /sys/devices/system/cpu/cpu3/power/pm_qos_resume_latency_us:0 > > Next I use dev_pm_qos_remove_request() to remove the previous latency > requirement (again with tracing and turbostat running). > > rmdir-665 [002] .... 686.925230: dev_pm_qos_remove_request: > device=cpu3 type=DEV_PM_QOS_RESUME_LATENCY new_value=-1 > rmdir-665 [002] .... 686.925250: pm_qos_update_target: > action=REMOVE_REQ prev_value=30 curr_value=2147483647 > rmdir-665 [002] .... 686.925254: dev_pm_qos_remove_request: > device=cpu2 type=DEV_PM_QOS_RESUME_LATENCY new_value=-1 > rmdir-665 [002] .... 686.925257: pm_qos_update_target: > action=REMOVE_REQ prev_value=30 curr_value=2147483647 > > Turbostat also shows that cores 2 and 3 return to their high residency in C6. > > As before, user API shows: > # grep . /sys/devices/system/cpu/cpu?/power/pm_qos_resume_latency_us > /sys/devices/system/cpu/cpu0/power/pm_qos_resume_latency_us:0 > /sys/devices/system/cpu/cpu1/power/pm_qos_resume_latency_us:0 > /sys/devices/system/cpu/cpu2/power/pm_qos_resume_latency_us:0 > /sys/devices/system/cpu/cpu3/power/pm_qos_resume_latency_us:0 > > > Thank you very much for making this work! > > Tested-by: Reinette Chatre <reinette.cha...@intel.com>
Thanks! Rafael
