Currently the minimal up_threshold is 11, and user may want to
use a smaller minimal up_threshold for performance tuning,
so MIN_FREQUENCY_UP_THRESHOLD could be set to 1 because:
1. Current systems wouldn't be affected as they have already
a value >= 11.
2. New systems with a default kernel would keep still the default
value that is >= 11.
Users now have the advantage that they can make their own decisions
and customize the 'trip point' to switch to the max frequency.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=65501
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The earlier implementation of governors used background timers and so
functions, mutex, etc had 'timer' keyword in their names.
But that's not true anymore. Replace 'timer' with 'update', as those
functions, variables are based around updates to frequency.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This patch migrates few users of cpufreq tables to the new helpers
that work on sorted freq-tables.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This routine can't fail unless the frequency table is invalid and
doesn't contain any valid entries.
Make it return the index and WARN() in case it is used for an invalid
table.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The policy already has this pointer set, use it instead.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
There is absolutely no need to keep a copy to the freq-table in 'struct
od_policy_dbs_info'. Use policy->freq_table instead.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Most of the callers of cpufreq_frequency_get_table() already have the
pointer to a valid 'policy' structure and they don't really need to go
through the per-cpu variable first and then a check to validate the
frequency, in order to find the freq-table for the policy.
Directly use the policy->freq_table field instead for them.
Only one user of that API is left after above changes, cpu_cooling.c and
it accesses the freq_table in a racy way as the policy can get freed in
between.
Fix it by using cpufreq_cpu_get() properly.
Since there are no more users of cpufreq_frequency_get_table() left, get
rid of it.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Javi Merino <javi.merino@arm.com> (cpu_cooling.c)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The 'initialized' field in struct cpufreq_governor is only used by
the conservative governor (as a usage counter) and the way that
happens is far from straightforward and arguably incorrect.
Namely, the value of 'initialized' is checked by
cpufreq_dbs_governor_init() and cpufreq_dbs_governor_exit() and
the results of those checks are passed (as the second argument) to
the ->init() and ->exit() callbacks in struct dbs_governor. Those
callbacks are only implemented by the ondemand and conservative
governors and ondemand doesn't use their second argument at all.
In turn, the conservative governor uses it to decide whether or not
to either register or unregister a transition notifier.
That whole mechanism is not only unnecessarily convoluted, but also
racy, because the 'initialized' field of struct cpufreq_governor is
updated in cpufreq_init_governor() and cpufreq_exit_governor() under
policy->rwsem which doesn't help if one of these functions is run
twice in parallel for different policies (which isn't impossible in
principle), for example.
Instead of it, add a proper usage counter to the conservative
governor and update it from cs_init() and cs_exit() which is
guaranteed to be non-racy, as those functions are only called
under gov_dbs_data_mutex which is global.
With that in place, drop the 'initialized' field from struct
cpufreq_governor as it is not used any more.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
These aren't required anymore as the allocation core already prints such
messages. Remove the redundant ones.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The design of the cpufreq governor API is not very straightforward,
as struct cpufreq_governor provides only one callback to be invoked
from different code paths for different purposes. The purpose it is
invoked for is determined by its second "event" argument, causing it
to act as a "callback multiplexer" of sorts.
Unfortunately, that leads to extra complexity in governors, some of
which implement the ->governor() callback as a switch statement
that simply checks the event argument and invokes a separate function
to handle that specific event.
That extra complexity can be eliminated by replacing the all-purpose
->governor() callback with a family of callbacks to carry out specific
governor operations: initialization and exit, start and stop and policy
limits updates. That also turns out to reduce the code size too, so
do it.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
In addition to fields representing governor tunables, struct dbs_data
contains some fields needed for the management of objects of that
type. As it turns out, that part of struct dbs_data may be shared
with (future) governors that won't use the common code used by
"ondemand" and "conservative", so move it to a separate struct type
and modify the code using struct dbs_data to follow.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
After previous changes there is only one piece of code in the
ondemand governor making references to per-CPU data structures,
but it can be easily modified to avoid doing that, so modify it
accordingly and move the definition of per-CPU data used by the
ondemand and conservative governors to the common code. Next,
change that code to access the per-CPU data structures directly
rather than via a governor callback.
This causes the ->get_cpu_cdbs governor callback to become
unnecessary, so drop it along with the macro and function
definitions related to it.
Finally, drop the definitions of struct od_cpu_dbs_info_s and
struct cs_cpu_dbs_info_s that aren't necessary any more.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Some fields in struct od_cpu_dbs_info_s and struct cs_cpu_dbs_info_s
are only used for a limited set of CPUs. Namely, if a policy is
shared between multiple CPUs, those fields will only be used for one
of them (policy->cpu). This means that they really are per-policy
rather than per-CPU and holding room for them in per-CPU data
structures is generally wasteful. Also moving those fields into
per-policy data structures will allow some significant simplifications
to be made going forward.
For this reason, introduce struct cs_policy_dbs_info and
struct od_policy_dbs_info to hold those fields. Define each of the
new structures as an extension of struct policy_dbs_info (such that
struct policy_dbs_info is embedded in each of them) and introduce
new ->alloc and ->free governor callbacks to allocate and free
those structures, respectively, such that ->alloc() will return
a pointer to the struct policy_dbs_info embedded in the allocated
data structure and ->free() will take that pointer as its argument.
With that, modify the code accessing the data fields in question
in per-CPU data objects to look for them in the new structures
via the struct policy_dbs_info pointer available to it and drop
them from struct od_cpu_dbs_info_s and struct cs_cpu_dbs_info_s.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
The ondemand_powersave_bias_init() function used for resetting data
fields related to the powersave bias tunable of the ondemand governor
works by walking all of the online CPUs in the system and updating the
od_cpu_dbs_info_s structures for all of them.
However, if governor tunables are per policy, the update should not
touch the CPUs that are not associated with the given dbs_data.
Moreover, since the data fields in question are only ever used for
policy->cpu in each policy governed by ondemand, the update can be
limited to those specific CPUs.
Rework the code to take the above observations into account.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
The ->store() callbacks of some tunable sysfs attributes of the
ondemand and conservative governors trigger immediate updates of
the CPU load information for all CPUs "governed" by the given
dbs_data by walking the cpu_dbs_info structures for all online
CPUs in the system and updating them.
This is questionable for two reasons. First, it may lead to a lot of
extra overhead on a system with many CPUs if the given dbs_data is
only associated with a few of them. Second, if governor tunables are
per-policy, the CPUs associated with the other sets of governor
tunables should not be updated.
To address this issue, use the observation that in all of the places
in question the update operation may be carried out in the same way
(because all of the tunables involved are now located in struct
dbs_data and readily available to the common code) and make the
code in those places invoke the same (new) helper function that
will carry out the update correctly.
That new function always checks the ignore_nice_load tunable value
and updates the CPUs' prev_cpu_nice data fields if that's set, which
wasn't done by the original code in store_io_is_busy(), but it
should have been done in there too.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
The ->powersave_bias_init_cpu callback in struct od_ops is only used
in one place and that invocation may be replaced with a direct call
to the function pointed to by that callback, so change the code
accordingly and drop the callback.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
After some previous changes, the ->get_cpu_dbs_info_s governor
callback and the "governor" field in struct dbs_governor (whose
value represents the governor type) are not used any more, so
drop them.
Also drop the unused gov_ops field from struct dbs_governor.
No functional changes.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
To avoid having to check the governor type explicitly in the common
code in order to initialize data structures specific to the governor
type properly, add a ->start callback to struct dbs_governor and
use it to initialize those data structures for the ondemand and
conservative governors.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
The io_is_busy governor tunable is only used by the ondemand governor
and is located in the ondemand-specific data structure, but it is
looked at by the common governor code that has to do ugly things to
get to that value, so move it to struct dbs_data and modify ondemand
accordingly.
Since the conservative governor never touches that field, it will
be always 0 for that governor and it won't have any effect on the
results of computations in that case.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
The ->freq_increase callback in struct od_ops is never invoked,
so drop it.
No functional changes.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Drop some lines of code from od_update() by arranging the statements
in there in a more logical way.
No functional changes.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Do not convert microseconds to jiffies and the other way around
in governor computations related to the sampling rate and sample
delay and drop delay_for_sampling_rate() which isn't of any use
then.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reduce the indentation level in the conditionals in od_dbs_timer()
and drop the delay variable from it.
No functional changes.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
The rate_mult field in struct od_cpu_dbs_info_s is used by the code
shared with the conservative governor and to access it that code
has to do an ugly governor type check. However, first of all it
is ever only used for policy->cpu, so it is per-policy rather than
per-CPU and second, it is initialized to 1 by cpufreq_governor_start(),
so if the conservative governor never modifies it, it will have no
effect on the results of any computations.
For these reasons, move rate_mult to struct policy_dbs_info (as a
common field).
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
The way the ->gov_check_cpu governor callback is used by the ondemand
and conservative governors is not really straightforward. Namely, the
governor calls dbs_check_cpu() that updates the load information for
the policy and the invokes ->gov_check_cpu() for the governor.
To get rid of that entanglement, notice that cpufreq_governor_limits()
doesn't need to call dbs_check_cpu() directly. Instead, it can simply
reset the sample delay to 0 which will cause a sample to be taken
immediately. The result of that is practically equivalent to calling
dbs_check_cpu() except that it will trigger a full update of governor
internal state and not just the ->gov_check_cpu() part.
Following that observation, make cpufreq_governor_limits() reset
the sample delay and turn dbs_check_cpu() into a function that will
simply evaluate the load and return the result called dbs_update().
That function can now be called by governors from the routines that
previously were pointed to by ->gov_check_cpu and those routines
can be called directly by each governor instead of dbs_check_cpu().
This way ->gov_check_cpu becomes unnecessary, so drop it.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Avoid extra checks in od_dbs_timer() by rearranging updates to the
local delay variable in it.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The ondemand governor already updates sample_delay_ns immediately on
updates to the sampling rate, but conservative doesn't do that.
It was left out earlier as the code was really too complex to get
that done easily. Things are sorted out very well now, however, and
the conservative governor can be modified to follow ondemand in that
respect.
Moreover, since the code needed to implement that in the
conservative governor would be identical to the corresponding
ondemand governor's code, make that code common and change both
governors to use it.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Tested-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The dbs_data_mutex lock is currently used in two places. First,
cpufreq_governor_dbs() uses it to guarantee mutual exclusion between
invocations of governor operations from the core. Second, it is used by
ondemand governor's update_sampling_rate() to ensure the stability of
data structures walked by it.
The second usage is quite problematic, because update_sampling_rate() is
called from a governor sysfs attribute's ->store callback and that leads
to a deadlock scenario involving cpufreq_governor_exit() which runs
under dbs_data_mutex. Thus it is better to rework the code so
update_sampling_rate() doesn't need to acquire dbs_data_mutex.
To that end, rework update_sampling_rate() to walk a list of policy_dbs
objects supported by the dbs_data one it has been called for (instead of
walking cpu_dbs_info object for all CPUs). The list manipulation is
protected with dbs_data->mutex which also is held around the execution
of update_sampling_rate(), it is not necessary to hold dbs_data_mutex in
that function any more.
Reported-by: Juri Lelli <juri.lelli@arm.com>
Reported-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The ondemand and conservative governors use the global-attr or freq-attr
structures to represent sysfs attributes corresponding to their tunables
(which of them is actually used depends on whether or not different
policy objects can use the same governor with different tunables at the
same time and, consequently, on where those attributes are located in
sysfs).
Unfortunately, in the freq-attr case, the standard cpufreq show/store
sysfs attribute callbacks are applied to the governor tunable attributes
and they always acquire the policy->rwsem lock before carrying out the
operation. That may lead to an ABBA deadlock if governor tunable
attributes are removed under policy->rwsem while one of them is being
accessed concurrently (if sysfs attributes removal wins the race, it
will wait for the access to complete with policy->rwsem held while the
attribute callback will block on policy->rwsem indefinitely).
We attempted to address this issue by dropping policy->rwsem around
governor tunable attributes removal (that is, around invocations of the
->governor callback with the event arg equal to CPUFREQ_GOV_POLICY_EXIT)
in cpufreq_set_policy(), but that opened up race conditions that had not
been possible with policy->rwsem held all the time. Therefore
policy->rwsem cannot be dropped in cpufreq_set_policy() at any point,
but the deadlock situation described above must be avoided too.
To that end, use the observation that in principle governor tunables may
be represented by the same data type regardless of whether the governor
is system-wide or per-policy and introduce a new structure, struct
governor_attr, for representing them and new corresponding macros for
creating show/store sysfs callbacks for them. Also make their parent
kobject use a new kobject type whose default show/store callbacks are
not related to the standard core cpufreq ones in any way (and they don't
acquire policy->rwsem in particular).
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Tested-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[ rjw: Subject & changelog + rebase ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
There are a few common tunables shared between the ondemand and
conservative governors. Move them to struct dbs_data to simplify
code.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Tested-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Some tunables are present in governor-specific structures, whereas one
(min_sampling_rate) is located directly in struct dbs_data.
There is a special macro for creating its sysfs attribute and the
show/store callbacks, but since more tunables are going to be moved
to struct dbs_data, a new generic macro for such cases will be useful,
so add it and use it for min_sampling_rate.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Tested-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The struct policy_dbs_info objects representing per-policy governor
data are not accessible directly from the corresponding policy
objects. To access them, one has to get a pointer to the
struct cpu_dbs_info of policy->cpu and use the policy_dbs field of
that which isn't really straightforward.
To address that rearrange the governor data structures so the
governor_data pointer in struct cpufreq_policy will point to
struct policy_dbs_info (instead of struct dbs_data) and that will
contain a pointer to struct dbs_data.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Since policy->cpu is always passed as the second argument to
dbs_check_cpu(), it is not really necessary to pass it, because
the function can obtain that value via its first argument just fine.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
The struct cpu_common_dbs_info structure represents the per-policy
part of the governor data (for the ondemand and conservative
governors), but its name doesn't reflect its purpose.
Rename it to struct policy_dbs_info and rename variables related to
it accordingly.
No functional changes.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Since it is possible to obtain a pointer to struct dbs_governor
from a pointer to the struct governor embedded in it with the help
of container_of(), the additional gov pointer in struct dbs_data
isn't really necessary.
Drop that pointer and make the code using it reach the dbs_governor
object via policy->governor.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Since it is possible to obtain a pointer to struct dbs_governor
from a pointer to the struct governor embedded in it via
container_of(), the second argument of cpufreq_governor_init()
is not necessary. Accordingly, cpufreq_governor_dbs() doesn't
need its second argument either and the ->governor callbacks
for both the ondemand and conservative governors may be set
to cpufreq_governor_dbs() directly. Make that happen.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Saravana Kannan <skannan@codeaurora.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
The ondemand and conservative governors are represented by
struct common_dbs_data whose name doesn't reflect the purpose it
is used for, so rename it to struct dbs_governor and rename
variables of that type accordingly.
No functional changes.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
For the ondemand and conservative governors (generally, governors
that use the common code in cpufreq_governor.c), there are two static
data structures representing the governor, the struct governor
structure (the interface to the cpufreq core) and the struct
common_dbs_data one (the interface to the cpufreq_governor.c code).
There's no fundamental reason why those two structures have to be
separate. Moreover, if the struct governor one is included into
struct common_dbs_data, it will be possible to reach the latter from
the policy via its policy->governor pointer, so it won't be necessary
to pass a separate pointer to it around. For this reason, embed
struct governor in struct common_dbs_data.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Saravana Kannan <skannan@codeaurora.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Every governor relying on the common code in cpufreq_governor.c
has to provide its own mutex in struct common_dbs_data. However,
there actually is no need to have a separate mutex per governor
for this purpose, they may be using the same global mutex just
fine. Accordingly, introduce a single common mutex for that and
drop the mutex field from struct common_dbs_data.
That at least will ensure that the mutex is always present and
initialized regardless of what the particular governors do.
Another benefit is that the common code does not need a pointer to
a governor-related structure to get to the mutex which sometimes
helps.
Finally, it makes the code generally easier to follow.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Saravana Kannan <skannan@codeaurora.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Instead of using a per-CPU deferrable timer for queuing up governor
work items, register a utilization update callback that will be
invoked from the scheduler on utilization changes.
The sampling rate is still the same as what was used for the
deferrable timers and the added irq_work overhead should be offset by
the eliminated timers overhead, so in theory the functional impact of
this patch should not be significant.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
The preprocessor magic used for setting the default cpufreq governor
(and for using the performance governor as a fallback one for that
matter) is really nasty, so replace it with __weak functions and
overrides.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Saravana Kannan <skannan@codeaurora.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Currently update_sampling_rate() runs over each online CPU and
cancels/queues timers on all policy->cpus every time. This should be
done just once for any cpu belonging to a policy.
Create a cpumask and keep on clearing it as and when we process
policies, so that we don't have to traverse through all CPUs of the same
policy.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
cpufreq governors evaluate load at sampling rate and based on that they
update frequency for a group of CPUs belonging to the same cpufreq
policy.
This is required to be done in a single thread for all policy->cpus, but
because we don't want to wakeup idle CPUs to do just that, we use
deferrable work for this. If we would have used a single delayed
deferrable work for the entire policy, there were chances that the CPU
required to run the handler can be in idle and we might end up not
changing the frequency for the entire group with load variations.
And so we were forced to keep per-cpu works, and only the one that
expires first need to do the real work and others are rescheduled for
next sampling time.
We have been using the more complex solution until now, where we used a
delayed deferrable work for this, which is a combination of a timer and
a work.
This could be made lightweight by keeping per-cpu deferred timers with a
single work item, which is scheduled by the first timer that expires.
This patch does just that and here are important changes:
- The timer handler will run in irq context and so we need to use a
spin_lock instead of the timer_mutex. And so a separate timer_lock is
created. This also makes the use of the mutex and lock quite clear, as
we know what exactly they are protecting.
- A new field 'skip_work' is added to track when the timer handlers can
queue a work. More comments present in code.
Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Pass 'policy' as argument to ->gov_dbs_timer() instead of cdbs and
dbs_data.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
We are guaranteed to have works scheduled for policy->cpus, as the
policy isn't stopped yet. And so there is no need to check that again.
Drop it.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
We are comparing policy->governor against cpufreq_gov_ondemand to make
sure that we update sampling rate only for the concerned CPUs. But that
isn't enough.
In case of governor_per_policy, there can be multiple instances of
ondemand governor and we will always end up updating all of them with
current code. What we rather need to do, is to compare dbs_data with
poilcy->governor_data, which will match only for the policies governed
by dbs_data.
This code is also racy as the governor might be getting stopped at that
time and we may end up scheduling work for a policy, which we have just
disabled.
Fix that by protecting the entire function with &od_dbs_cdata.mutex,
which will prevent against races with policy START/STOP/etc.
After these locks are in place, we can safely get the policy via per-cpu
dbs_info.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
'timer_mutex' is required to sync work-handlers of policy->cpus.
update_sampling_rate() is just canceling the works and queuing them
again. This isn't protecting anything at all in update_sampling_rate()
and is not gonna be of any use.
Even if a work-handler is already running for a CPU,
cancel_delayed_work_sync() will wait for it to finish.
Drop these unnecessary locks.
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Some part of cs_dbs_timer() and od_dbs_timer() is exactly same and is
unnecessarily duplicated.
Create the real work-handler in cpufreq_governor.c and put the common
code in this routine (dbs_timer()).
Shouldn't make any functional change.
Reviewed-and-tested-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Some information is common to all CPUs belonging to a policy, but are
kept on per-cpu basis. Lets keep that in another structure common to all
policy->cpus. That will make updates/reads to that less complex and less
error prone.
The memory for cpu_common_dbs_info is allocated/freed at INIT/EXIT, so
that it we don't reallocate it for STOP/START sequence. It will be also
be used (in next patch) while the governor is stopped and so must not be
freed that early.
Reviewed-and-tested-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Just call it 'policy', cur_policy is unnecessarily long and doesn't
have any special meaning.
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
