From 3654654f7aa79a37dde130afb7409c55b11807e7 Mon Sep 17 00:00:00 2001 From: Jan Engelhardt Date: Tue, 16 Nov 2010 09:52:32 -0800 Subject: netlink: let nlmsg and nla functions take pointer-to-const args The changed functions do not modify the NL messages and/or attributes at all. They should use const (similar to strchr), so that callers which have a const nlmsg/nlattr around can make use of them without casting. While at it, constify a data array. Signed-off-by: Jan Engelhardt Signed-off-by: David S. Miller --- lib/nlattr.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) (limited to 'lib') diff --git a/lib/nlattr.c b/lib/nlattr.c index c4706eb98d3d..00e8a02681a6 100644 --- a/lib/nlattr.c +++ b/lib/nlattr.c @@ -15,7 +15,7 @@ #include #include -static u16 nla_attr_minlen[NLA_TYPE_MAX+1] __read_mostly = { +static const u16 nla_attr_minlen[NLA_TYPE_MAX+1] = { [NLA_U8] = sizeof(u8), [NLA_U16] = sizeof(u16), [NLA_U32] = sizeof(u32), @@ -23,7 +23,7 @@ static u16 nla_attr_minlen[NLA_TYPE_MAX+1] __read_mostly = { [NLA_NESTED] = NLA_HDRLEN, }; -static int validate_nla(struct nlattr *nla, int maxtype, +static int validate_nla(const struct nlattr *nla, int maxtype, const struct nla_policy *policy) { const struct nla_policy *pt; @@ -115,10 +115,10 @@ static int validate_nla(struct nlattr *nla, int maxtype, * * Returns 0 on success or a negative error code. */ -int nla_validate(struct nlattr *head, int len, int maxtype, +int nla_validate(const struct nlattr *head, int len, int maxtype, const struct nla_policy *policy) { - struct nlattr *nla; + const struct nlattr *nla; int rem, err; nla_for_each_attr(nla, head, len, rem) { @@ -173,10 +173,10 @@ nla_policy_len(const struct nla_policy *p, int n) * * Returns 0 on success or a negative error code. */ -int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len, - const struct nla_policy *policy) +int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head, + int len, const struct nla_policy *policy) { - struct nlattr *nla; + const struct nlattr *nla; int rem, err; memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1)); @@ -191,7 +191,7 @@ int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len, goto errout; } - tb[type] = nla; + tb[type] = (struct nlattr *)nla; } } @@ -212,14 +212,14 @@ errout: * * Returns the first attribute in the stream matching the specified type. */ -struct nlattr *nla_find(struct nlattr *head, int len, int attrtype) +struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype) { - struct nlattr *nla; + const struct nlattr *nla; int rem; nla_for_each_attr(nla, head, len, rem) if (nla_type(nla) == attrtype) - return nla; + return (struct nlattr *)nla; return NULL; } -- cgit v1.2.3 From c5485a7e7569ab32eea240c850198519e2a765ef Mon Sep 17 00:00:00 2001 From: Bruno Randolf Date: Tue, 16 Nov 2010 10:58:37 +0900 Subject: 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 Reviewed-by: KOSAKI Motohiro Signed-off-by: John W. Linville --- include/linux/average.h | 32 +++++++++++++++++++++++++++ lib/Kconfig | 3 +++ lib/Makefile | 2 ++ lib/average.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 94 insertions(+) create mode 100644 include/linux/average.h create mode 100644 lib/average.c (limited to 'lib') diff --git a/include/linux/average.h b/include/linux/average.h new file mode 100644 index 000000000000..7706e40f95fa --- /dev/null +++ b/include/linux/average.h @@ -0,0 +1,32 @@ +#ifndef _LINUX_AVERAGE_H +#define _LINUX_AVERAGE_H + +#include + +/* Exponentially weighted moving average (EWMA) */ + +/* For more documentation see lib/average.c */ + +struct ewma { + unsigned long internal; + unsigned long factor; + unsigned long weight; +}; + +extern void ewma_init(struct ewma *avg, unsigned long factor, + unsigned long weight); + +extern struct ewma *ewma_add(struct ewma *avg, unsigned long val); + +/** + * ewma_read() - Get average value + * @avg: Average structure + * + * Returns the average value held in @avg. + */ +static inline unsigned long ewma_read(const struct ewma *avg) +{ + return DIV_ROUND_CLOSEST(avg->internal, avg->factor); +} + +#endif /* _LINUX_AVERAGE_H */ diff --git a/lib/Kconfig b/lib/Kconfig index fa9bf2c06199..3116aa631af6 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -210,4 +210,7 @@ config GENERIC_ATOMIC64 config LRU_CACHE tristate +config AVERAGE + bool + endmenu diff --git a/lib/Makefile b/lib/Makefile index e6a3763b8212..76d3b8514903 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -106,6 +106,8 @@ obj-$(CONFIG_GENERIC_ATOMIC64) += atomic64.o obj-$(CONFIG_ATOMIC64_SELFTEST) += atomic64_test.o +obj-$(CONFIG_AVERAGE) += average.o + hostprogs-y := gen_crc32table clean-files := crc32table.h diff --git a/lib/average.c b/lib/average.c new file mode 100644 index 000000000000..f1d1b4660c42 --- /dev/null +++ b/lib/average.c @@ -0,0 +1,57 @@ +/* + * lib/average.c + * + * This source code is licensed under the GNU General Public License, + * Version 2. See the file COPYING for more details. + */ + +#include +#include +#include + +/** + * DOC: Exponentially Weighted Moving Average (EWMA) + * + * These are generic functions for calculating Exponentially Weighted Moving + * Averages (EWMA). We keep a structure with the EWMA parameters and a scaled + * up internal representation of the average value to prevent rounding errors. + * The factor for scaling up and the exponential weight (or decay rate) have to + * be specified thru the init fuction. The structure should not be accessed + * directly but only thru the helper functions. + */ + +/** + * ewma_init() - Initialize EWMA parameters + * @avg: Average structure + * @factor: Factor to use for the scaled up internal value. The maximum value + * of averages can be ULONG_MAX/(factor*weight). + * @weight: Exponential weight, or decay rate. This defines how fast the + * influence of older values decreases. Has to be bigger than 1. + * + * Initialize the EWMA parameters for a given struct ewma @avg. + */ +void ewma_init(struct ewma *avg, unsigned long factor, unsigned long weight) +{ + WARN_ON(weight <= 1 || factor == 0); + avg->internal = 0; + avg->weight = weight; + avg->factor = factor; +} +EXPORT_SYMBOL(ewma_init); + +/** + * ewma_add() - Exponentially weighted moving average (EWMA) + * @avg: Average structure + * @val: Current value + * + * Add a sample to the average. + */ +struct ewma *ewma_add(struct ewma *avg, unsigned long val) +{ + avg->internal = avg->internal ? + (((avg->internal * (avg->weight - 1)) + + (val * avg->factor)) / avg->weight) : + (val * avg->factor); + return avg; +} +EXPORT_SYMBOL(ewma_add); -- cgit v1.2.3 From af5568843594fb71055debe36e521fa8072fcecc Mon Sep 17 00:00:00 2001 From: Bruno Randolf Date: Thu, 2 Dec 2010 19:50:37 +0900 Subject: lib: Improve EWMA efficiency by using bitshifts Using bitshifts instead of division and multiplication should improve performance. That requires weight and factor to be powers of two, but i think this is something we can live with. Thanks to Peter Zijlstra for the improved formula! Signed-off-by: Bruno Randolf -- v2: use log2.h functions Signed-off-by: John W. Linville --- include/linux/average.h | 4 +--- lib/average.c | 20 ++++++++++++-------- 2 files changed, 13 insertions(+), 11 deletions(-) (limited to 'lib') diff --git a/include/linux/average.h b/include/linux/average.h index 7706e40f95fa..c6028fd742c1 100644 --- a/include/linux/average.h +++ b/include/linux/average.h @@ -1,8 +1,6 @@ #ifndef _LINUX_AVERAGE_H #define _LINUX_AVERAGE_H -#include - /* Exponentially weighted moving average (EWMA) */ /* For more documentation see lib/average.c */ @@ -26,7 +24,7 @@ extern struct ewma *ewma_add(struct ewma *avg, unsigned long val); */ static inline unsigned long ewma_read(const struct ewma *avg) { - return DIV_ROUND_CLOSEST(avg->internal, avg->factor); + return avg->internal >> avg->factor; } #endif /* _LINUX_AVERAGE_H */ diff --git a/lib/average.c b/lib/average.c index f1d1b4660c42..5576c2841496 100644 --- a/lib/average.c +++ b/lib/average.c @@ -8,6 +8,7 @@ #include #include #include +#include /** * DOC: Exponentially Weighted Moving Average (EWMA) @@ -24,18 +25,21 @@ * ewma_init() - Initialize EWMA parameters * @avg: Average structure * @factor: Factor to use for the scaled up internal value. The maximum value - * of averages can be ULONG_MAX/(factor*weight). + * of averages can be ULONG_MAX/(factor*weight). For performance reasons + * factor has to be a power of 2. * @weight: Exponential weight, or decay rate. This defines how fast the - * influence of older values decreases. Has to be bigger than 1. + * influence of older values decreases. For performance reasons weight has + * to be a power of 2. * * Initialize the EWMA parameters for a given struct ewma @avg. */ void ewma_init(struct ewma *avg, unsigned long factor, unsigned long weight) { - WARN_ON(weight <= 1 || factor == 0); + WARN_ON(!is_power_of_2(weight) || !is_power_of_2(factor)); + + avg->weight = ilog2(weight); + avg->factor = ilog2(factor); avg->internal = 0; - avg->weight = weight; - avg->factor = factor; } EXPORT_SYMBOL(ewma_init); @@ -49,9 +53,9 @@ EXPORT_SYMBOL(ewma_init); struct ewma *ewma_add(struct ewma *avg, unsigned long val) { avg->internal = avg->internal ? - (((avg->internal * (avg->weight - 1)) + - (val * avg->factor)) / avg->weight) : - (val * avg->factor); + (((avg->internal << avg->weight) - avg->internal) + + (val << avg->factor)) >> avg->weight : + (val << avg->factor); return avg; } EXPORT_SYMBOL(ewma_add); -- cgit v1.2.3