From patchwork Tue Nov 16 01:58:37 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bruno Randolf X-Patchwork-Id: 326802 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter1.kernel.org (8.14.4/8.14.3) with ESMTP id oAG1wMHq021238 for ; Tue, 16 Nov 2010 01:58:22 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759132Ab0KPB6U (ORCPT ); Mon, 15 Nov 2010 20:58:20 -0500 Received: from mail30g.wh2.ocn.ne.jp ([220.111.41.239]:42651 "HELO mail30g.wh2.ocn.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754986Ab0KPB6U (ORCPT ); Mon, 15 Nov 2010 20:58:20 -0500 Received: from vs3016.wh2.ocn.ne.jp (125.206.180.189) by mail30g.wh2.ocn.ne.jp (RS ver 1.0.95vs) with SMTP id 0-0732952698 for ; Tue, 16 Nov 2010 10:58:19 +0900 (JST) Received: (qmail 33183 invoked from network); 16 Nov 2010 01:58:17 -0000 Received: from unknown (HELO localhost6.localdomain6) (220.110.201.18) by with SMTP; 16 Nov 2010 01:58:17 -0000 Subject: [PATCH v8 1/3] Add generic exponentially weighted moving average (EWMA) function To: linville@tuxdriver.com From: Bruno Randolf Cc: randy.dunlap@oracle.com, br1@thinktube.com, peterz@infradead.org, blp@cs.stanford.edu, linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, Lars_Ericsson@telia.com, stefanr@s5r6.in-berlin.de, kosaki.motohiro@jp.fujitsu.com, akpm@linux-foundation.org, kevin.granade@gmail.com Date: Tue, 16 Nov 2010 10:58:37 +0900 Message-ID: <20101116015837.21081.79264.stgit@localhost6.localdomain6> User-Agent: StGit/0.15 MIME-Version: 1.0 X-SF-Loop: 1 Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.3 (demeter1.kernel.org [140.211.167.41]); Tue, 16 Nov 2010 01:58:22 +0000 (UTC) diff --git a/include/linux/average.h b/include/linux/average.h new file mode 100644 index 0000000..7706e40 --- /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 fa9bf2c..3116aa6 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 e6a3763..76d3b85 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 0000000..f1d1b46 --- /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);