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linux_old1/include/linux/average.h

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lib: Add generic exponentially weighted moving average (EWMA) function This adds generic functions for calculating Exponentially Weighted Moving Averages (EWMA). This implementation makes use of a structure which keeps the EWMA parameters and a scaled up internal representation to reduce rounding errors. The original idea for this implementation came from the rt2x00 driver (rt2x00link.c). I would like to use it in several places in the mac80211 and ath5k code and I hope it can be useful in many other places in the kernel code. Signed-off-by: Bruno Randolf <br1@einfach.org> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>
2010-11-16 09:58:37 +08:00
#ifndef _LINUX_AVERAGE_H
#define _LINUX_AVERAGE_H
average: change to declare precision, not factor Declaring the factor is counter-intuitive, and people are prone to using small(-ish) values even when that makes no sense. Change the DECLARE_EWMA() macro to take the fractional precision, in bits, rather than a factor, and update all users. While at it, add some more documentation. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2017-02-15 16:49:26 +08:00
/*
* Exponentially weighted moving average (EWMA)
*
* This implements a fixed-precision EWMA algorithm, with both the
* precision and fall-off coefficient determined at compile-time
* and built into the generated helper funtions.
*
* The first argument to the macro is the name that will be used
* for the struct and helper functions.
*
* The second argument, the precision, expresses how many bits are
* used for the fractional part of the fixed-precision values.
*
* The third argument, the weight reciprocal, determines how the
* new values will be weighed vs. the old state, new values will
* get weight 1/weight_rcp and old values 1-1/weight_rcp. Note
* that this parameter must be a power of two for efficiency.
*/
lib: Add generic exponentially weighted moving average (EWMA) function This adds generic functions for calculating Exponentially Weighted Moving Averages (EWMA). This implementation makes use of a structure which keeps the EWMA parameters and a scaled up internal representation to reduce rounding errors. The original idea for this implementation came from the rt2x00 driver (rt2x00link.c). I would like to use it in several places in the mac80211 and ath5k code and I hope it can be useful in many other places in the kernel code. Signed-off-by: Bruno Randolf <br1@einfach.org> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>
2010-11-16 09:58:37 +08:00
average: change to declare precision, not factor Declaring the factor is counter-intuitive, and people are prone to using small(-ish) values even when that makes no sense. Change the DECLARE_EWMA() macro to take the fractional precision, in bits, rather than a factor, and update all users. While at it, add some more documentation. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2017-02-15 16:49:26 +08:00
#define DECLARE_EWMA(name, _precision, _weight_rcp) \
average: provide macro to create static EWMA Having the EWMA parameters stored in the runtime struct imposes memory requirements for the constant values that could just be inlined in the code. This particularly makes sense if there are a lot of such structs, for example in mac80211 in the station table where each station has a number of these in an array, and there can be many stations. Provide a macro DECLARE_EWMA() that declares the necessary struct and inline functions to access it with the parameters hard-coded; using this also means the user no longer needs to 'select AVERAGE' as it's entirely self-contained. In the mac80211 case, on x86-64, this actually slightly *reduces* code size, while also saving 80 bytes of runtime memory per sta. Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2015-07-13 18:17:25 +08:00
struct ewma_##name { \
unsigned long internal; \
}; \
static inline void ewma_##name##_init(struct ewma_##name *e) \
{ \
average: change to declare precision, not factor Declaring the factor is counter-intuitive, and people are prone to using small(-ish) values even when that makes no sense. Change the DECLARE_EWMA() macro to take the fractional precision, in bits, rather than a factor, and update all users. While at it, add some more documentation. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2017-02-15 16:49:26 +08:00
BUILD_BUG_ON(!__builtin_constant_p(_precision)); \
BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \
/* \
* Even if you want to feed it just 0/1 you should have \
* some bits for the non-fractional part... \
*/ \
BUILD_BUG_ON((_precision) > 30); \
BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \
average: provide macro to create static EWMA Having the EWMA parameters stored in the runtime struct imposes memory requirements for the constant values that could just be inlined in the code. This particularly makes sense if there are a lot of such structs, for example in mac80211 in the station table where each station has a number of these in an array, and there can be many stations. Provide a macro DECLARE_EWMA() that declares the necessary struct and inline functions to access it with the parameters hard-coded; using this also means the user no longer needs to 'select AVERAGE' as it's entirely self-contained. In the mac80211 case, on x86-64, this actually slightly *reduces* code size, while also saving 80 bytes of runtime memory per sta. Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2015-07-13 18:17:25 +08:00
e->internal = 0; \
} \
static inline unsigned long \
ewma_##name##_read(struct ewma_##name *e) \
{ \
average: change to declare precision, not factor Declaring the factor is counter-intuitive, and people are prone to using small(-ish) values even when that makes no sense. Change the DECLARE_EWMA() macro to take the fractional precision, in bits, rather than a factor, and update all users. While at it, add some more documentation. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2017-02-15 16:49:26 +08:00
BUILD_BUG_ON(!__builtin_constant_p(_precision)); \
BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \
BUILD_BUG_ON((_precision) > 30); \
BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \
return e->internal >> (_precision); \
average: provide macro to create static EWMA Having the EWMA parameters stored in the runtime struct imposes memory requirements for the constant values that could just be inlined in the code. This particularly makes sense if there are a lot of such structs, for example in mac80211 in the station table where each station has a number of these in an array, and there can be many stations. Provide a macro DECLARE_EWMA() that declares the necessary struct and inline functions to access it with the parameters hard-coded; using this also means the user no longer needs to 'select AVERAGE' as it's entirely self-contained. In the mac80211 case, on x86-64, this actually slightly *reduces* code size, while also saving 80 bytes of runtime memory per sta. Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2015-07-13 18:17:25 +08:00
} \
static inline void ewma_##name##_add(struct ewma_##name *e, \
unsigned long val) \
{ \
unsigned long internal = ACCESS_ONCE(e->internal); \
average: change to declare precision, not factor Declaring the factor is counter-intuitive, and people are prone to using small(-ish) values even when that makes no sense. Change the DECLARE_EWMA() macro to take the fractional precision, in bits, rather than a factor, and update all users. While at it, add some more documentation. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2017-02-15 16:49:26 +08:00
unsigned long weight_rcp = ilog2(_weight_rcp); \
unsigned long precision = _precision; \
average: provide macro to create static EWMA Having the EWMA parameters stored in the runtime struct imposes memory requirements for the constant values that could just be inlined in the code. This particularly makes sense if there are a lot of such structs, for example in mac80211 in the station table where each station has a number of these in an array, and there can be many stations. Provide a macro DECLARE_EWMA() that declares the necessary struct and inline functions to access it with the parameters hard-coded; using this also means the user no longer needs to 'select AVERAGE' as it's entirely self-contained. In the mac80211 case, on x86-64, this actually slightly *reduces* code size, while also saving 80 bytes of runtime memory per sta. Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2015-07-13 18:17:25 +08:00
\
average: change to declare precision, not factor Declaring the factor is counter-intuitive, and people are prone to using small(-ish) values even when that makes no sense. Change the DECLARE_EWMA() macro to take the fractional precision, in bits, rather than a factor, and update all users. While at it, add some more documentation. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2017-02-15 16:49:26 +08:00
BUILD_BUG_ON(!__builtin_constant_p(_precision)); \
BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \
BUILD_BUG_ON((_precision) > 30); \
BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \
average: provide macro to create static EWMA Having the EWMA parameters stored in the runtime struct imposes memory requirements for the constant values that could just be inlined in the code. This particularly makes sense if there are a lot of such structs, for example in mac80211 in the station table where each station has a number of these in an array, and there can be many stations. Provide a macro DECLARE_EWMA() that declares the necessary struct and inline functions to access it with the parameters hard-coded; using this also means the user no longer needs to 'select AVERAGE' as it's entirely self-contained. In the mac80211 case, on x86-64, this actually slightly *reduces* code size, while also saving 80 bytes of runtime memory per sta. Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2015-07-13 18:17:25 +08:00
\
ACCESS_ONCE(e->internal) = internal ? \
average: change to declare precision, not factor Declaring the factor is counter-intuitive, and people are prone to using small(-ish) values even when that makes no sense. Change the DECLARE_EWMA() macro to take the fractional precision, in bits, rather than a factor, and update all users. While at it, add some more documentation. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2017-02-15 16:49:26 +08:00
(((internal << weight_rcp) - internal) + \
(val << precision)) >> weight_rcp : \
(val << precision); \
average: provide macro to create static EWMA Having the EWMA parameters stored in the runtime struct imposes memory requirements for the constant values that could just be inlined in the code. This particularly makes sense if there are a lot of such structs, for example in mac80211 in the station table where each station has a number of these in an array, and there can be many stations. Provide a macro DECLARE_EWMA() that declares the necessary struct and inline functions to access it with the parameters hard-coded; using this also means the user no longer needs to 'select AVERAGE' as it's entirely self-contained. In the mac80211 case, on x86-64, this actually slightly *reduces* code size, while also saving 80 bytes of runtime memory per sta. Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2015-07-13 18:17:25 +08:00
}
lib: Add generic exponentially weighted moving average (EWMA) function This adds generic functions for calculating Exponentially Weighted Moving Averages (EWMA). This implementation makes use of a structure which keeps the EWMA parameters and a scaled up internal representation to reduce rounding errors. The original idea for this implementation came from the rt2x00 driver (rt2x00link.c). I would like to use it in several places in the mac80211 and ath5k code and I hope it can be useful in many other places in the kernel code. Signed-off-by: Bruno Randolf <br1@einfach.org> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>
2010-11-16 09:58:37 +08:00
#endif /* _LINUX_AVERAGE_H */