talos-op-linux/drivers/cpuidle/governors, branch master

cpuidle: teo: Fix intervals[] array indexing bug

2020-01-13T10:14:58+00:00

Fix a simple bug in rotating array index. Fixes: b26bf6ab716f ("cpuidle: New timer events oriented governor for tickless systems") Signed-off-by: Ikjoon Jang Cc: 5.1+ # 5.1+ Signed-off-by: Rafael J. Wysocki

cpuidle: teo: Avoid code duplication in conditionals

2019-11-14T23:54:33+00:00

There are three places in teo_select() where a given amount of time is compared with TICK_NSEC if tick_nohz_tick_stopped() returns true, which is a bit of duplicated code. Avoid that code duplication by defining a helper function to do the check and using it in all of the places in question. No intentional functional impact. Signed-off-by: Rafael J. Wysocki

cpuidle: teo: Avoid using "early hits" incorrectly

2019-11-13T21:31:17+00:00

If the current state with the maximum "early hits" metric in teo_select() is also the one "matching" the expected idle duration, it will be used as the candidate one for selection even if its "misses" metric is greater than its "hits" metric, which is not correct. In that case, the candidate state should be shallower than the current one and its "early hits" metric should be the maximum among the idle states shallower than the current one. To make that happen, modify teo_select() to save the index of the state whose "early hits" metric is the maximum for the range of states below the current one and go back to that state if it turns out that the current one should be rejected. Fixes: 159e48560f51 ("cpuidle: teo: Fix "early hits" handling for disabled idle states") Signed-off-by: Rafael J. Wysocki

cpuidle: teo: Exclude cpuidle overhead from computations

2019-11-13T21:31:17+00:00

One purpose of the computations in teo_update() is to determine whether or not the (saved) time till the next timer event and the measured idle duration fall into the same "bin", so avoid using values that include the cpuidle overhead to obtain the latter. Signed-off-by: Rafael J. Wysocki

cpuidle: Use nanoseconds as the unit of time

2019-11-11T20:56:07+00:00

Currently, the cpuidle subsystem uses microseconds as the unit of time which (among other things) causes the idle loop to incur some integer division overhead for no clear benefit. In order to allow cpuidle to measure time in nanoseconds, add two new fields, exit_latency_ns and target_residency_ns, to represent the exit latency and target residency of an idle state in nanoseconds, respectively, to struct cpuidle_state and initialize them with the help of the corresponding values in microseconds provided by drivers. Additionally, change cpuidle_governor_latency_req() to return the idle state exit latency constraint in nanoseconds. Also meeasure idle state residency (last_residency_ns in struct cpuidle_device and time_ns in struct cpuidle_driver) in nanoseconds and update the cpuidle core and governors accordingly. However, the menu governor still computes typical intervals in microseconds to avoid integer overflows. Signed-off-by: Rafael J. Wysocki Acked-by: Peter Zijlstra (Intel) Acked-by: Doug Smythies Tested-by: Doug Smythies

cpuidle: Consolidate disabled state checks

2019-11-06T12:19:56+00:00

There are two reasons why CPU idle states may be disabled: either because the driver has disabled them or because they have been disabled by user space via sysfs. In the former case, the state's "disabled" flag is set once during the initialization of the driver and it is never cleared later (it is read-only effectively). In the latter case, the "disable" field of the given state's cpuidle_state_usage struct is set and it may be changed via sysfs. Thus checking whether or not an idle state has been disabled involves reading these two flags every time. In order to avoid the additional check of the state's "disabled" flag (which is effectively read-only anyway), use the value of it at the init time to set a (new) flag in the "disable" field of that state's cpuidle_state_usage structure and use the sysfs interface to manipulate another (new) flag in it. This way the state is disabled whenever the "disable" field of its cpuidle_state_usage structure is nonzero, whatever the reason, and it is the only place to look into to check whether or not the state has been disabled. Signed-off-by: Rafael J. Wysocki Acked-by: Daniel Lezcano Acked-by: Peter Zijlstra (Intel)

cpuidle: teo: Fix "early hits" handling for disabled idle states

2019-10-14T08:40:33+00:00

The TEO governor uses idle duration "bins" defined in accordance with the CPU idle states table provided by the driver, so that each "bin" covers the idle duration range between the target residency of the idle state corresponding to it and the target residency of the closest deeper idle state. The governor collects statistics for each bin regardless of whether or not the idle state corresponding to it is currently enabled. In particular, the "early hits" metric measures the likelihood of a situation in which the idle duration measured after wakeup falls into to given bin, but the time till the next timer (sleep length) falls into a bin corresponding to one of the deeper idle states. It is used when the "hits" and "misses" metrics indicate that the state "matching" the sleep length should not be selected, so that the state with the maximum "early hits" value is selected instead of it. If the idle state corresponding to the given bin is disabled, it cannot be selected and if it turns out to be the one that should be selected, a shallower idle state needs to be used instead of it. Nevertheless, the metrics collected for the bin corresponding to it are still valid and need to be taken into account as though that state had not been disabled. As far as the "early hits" metric is concerned, teo_select() tries to take disabled states into account, but the state index corresponding to the maximum "early hits" value computed by it may be incorrect. Namely, it always uses the index of the previous maximum "early hits" state then, but there may be enabled idle states closer to the disabled one in question. In particular, if the current candidate state (whose index is the idx value) is closer to the disabled one and the "early hits" value of the disabled state is greater than the current maximum, the index of the current candidate state (idx) should replace the "maximum early hits state" index. Modify the code to handle that case correctly. Fixes: b26bf6ab716f ("cpuidle: New timer events oriented governor for tickless systems") Reported-by: Doug Smythies Signed-off-by: Rafael J. Wysocki Cc: 5.1+ # 5.1+

cpuidle: teo: Consider hits and misses metrics of disabled states

2019-10-14T08:40:33+00:00

The TEO governor uses idle duration "bins" defined in accordance with the CPU idle states table provided by the driver, so that each "bin" covers the idle duration range between the target residency of the idle state corresponding to it and the target residency of the closest deeper idle state. The governor collects statistics for each bin regardless of whether or not the idle state corresponding to it is currently enabled. In particular, the "hits" and "misses" metrics measure the likelihood of a situation in which both the time till the next timer (sleep length) and the idle duration measured after wakeup fall into the given bin. Namely, if the "hits" value is greater than the "misses" one, that situation is more likely than the one in which the sleep length falls into the given bin, but the idle duration measured after wakeup falls into a bin corresponding to one of the shallower idle states. If the idle state corresponding to the given bin is disabled, it cannot be selected and if it turns out to be the one that should be selected, a shallower idle state needs to be used instead of it. Nevertheless, the metrics collected for the bin corresponding to it are still valid and need to be taken into account as though that state had not been disabled. For this reason, make teo_select() always use the "hits" and "misses" values of the idle duration range that the sleep length falls into even if the specific idle state corresponding to it is disabled and if the "hits" values is greater than the "misses" one, select the closest enabled shallower idle state in that case. Fixes: b26bf6ab716f ("cpuidle: New timer events oriented governor for tickless systems") Signed-off-by: Rafael J. Wysocki Cc: 5.1+ # 5.1+

cpuidle: teo: Rename local variable in teo_select()

2019-10-14T08:40:33+00:00

Rename a local variable in teo_select() in preparation for subsequent code modifications, no intentional impact. Signed-off-by: Rafael J. Wysocki Cc: 5.1+ # 5.1+

cpuidle: teo: Ignore disabled idle states that are too deep

2019-10-14T08:40:32+00:00

Prevent disabled CPU idle state with target residencies beyond the anticipated idle duration from being taken into account by the TEO governor. Fixes: b26bf6ab716f ("cpuidle: New timer events oriented governor for tickless systems") Signed-off-by: Rafael J. Wysocki Cc: 5.1+ # 5.1+