[PATCH 0/4] average: convert users to inline implementation

[PATCH 0/4] average: convert users to inline implementation

[Johannes Berg]

Since there's very little benefit of the out-of-line implementation
(a single byte of .text in one driver as far as I've seen), convert
all drivers to the inline implementation, saving memory, and remove
the out-of-line implementation.

Perhaps the easiest would be for Dave to take all of these patches?

johannes

[PATCH 1/4] virtio_net: use DECLARE_EWMA

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

Instead of using the out-of-line EWMA calculation, use DECLARE_EWMA()
to create static inlines. On x86/64 this results in no change in code
size for me, but reduces the struct receive_queue size by the two
unsigned long values that store the parameters.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 drivers/net/Kconfig      |  1 -
 drivers/net/virtio_net.c | 22 +++++++++++-----------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index e58468b02987..f50373645ab4 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -282,7 +282,6 @@ config VETH
 config VIRTIO_NET
 	tristate "Virtio network driver"
 	depends on VIRTIO
-	select AVERAGE
 	---help---
 	  This is the virtual network driver for virtio.  It can be used with
 	  lguest or QEMU based VMMs (like KVM or Xen).  Say Y or M.
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 546b669fbfdd..9b950f2db836 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -40,12 +40,12 @@ module_param(gso, bool, 0444);
 #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
 #define GOOD_COPY_LEN	128
 
-/* Weight used for the RX packet size EWMA. The average packet size is used to
- * determine the packet buffer size when refilling RX rings. As the entire RX
- * ring may be refilled at once, the weight is chosen so that the EWMA will be
- * insensitive to short-term, transient changes in packet size.
+/* RX packet size EWMA. The average packet size is used to determine the packet
+ * buffer size when refilling RX rings. As the entire RX ring may be refilled
+ * at once, the weight is chosen so that the EWMA will be insensitive to short-
+ * term, transient changes in packet size.
  */
-#define RECEIVE_AVG_WEIGHT 64
+DECLARE_EWMA(pkt_len, 1, 64)
 
 /* Minimum alignment for mergeable packet buffers. */
 #define MERGEABLE_BUFFER_ALIGN max(L1_CACHE_BYTES, 256)
@@ -85,7 +85,7 @@ struct receive_queue {
 	struct page *pages;
 
 	/* Average packet length for mergeable receive buffers. */
-	struct ewma mrg_avg_pkt_len;
+	struct ewma_pkt_len mrg_avg_pkt_len;
 
 	/* Page frag for packet buffer allocation. */
 	struct page_frag alloc_frag;
@@ -407,7 +407,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		}
 	}
 
-	ewma_add(&rq->mrg_avg_pkt_len, head_skb->len);
+	ewma_pkt_len_add(&rq->mrg_avg_pkt_len, head_skb->len);
 	return head_skb;
 
 err_skb:
@@ -600,12 +600,12 @@ static int add_recvbuf_big(struct virtnet_info *vi, struct receive_queue *rq,
 	return err;
 }
 
-static unsigned int get_mergeable_buf_len(struct ewma *avg_pkt_len)
+static unsigned int get_mergeable_buf_len(struct ewma_pkt_len *avg_pkt_len)
 {
 	const size_t hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
 	unsigned int len;
 
-	len = hdr_len + clamp_t(unsigned int, ewma_read(avg_pkt_len),
+	len = hdr_len + clamp_t(unsigned int, ewma_pkt_len_read(avg_pkt_len),
 			GOOD_PACKET_LEN, PAGE_SIZE - hdr_len);
 	return ALIGN(len, MERGEABLE_BUFFER_ALIGN);
 }
@@ -1615,7 +1615,7 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
 		napi_hash_add(&vi->rq[i].napi);
 
 		sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg));
-		ewma_init(&vi->rq[i].mrg_avg_pkt_len, 1, RECEIVE_AVG_WEIGHT);
+		ewma_pkt_len_init(&vi->rq[i].mrg_avg_pkt_len);
 		sg_init_table(vi->sq[i].sg, ARRAY_SIZE(vi->sq[i].sg));
 	}
 
@@ -1658,7 +1658,7 @@ static ssize_t mergeable_rx_buffer_size_show(struct netdev_rx_queue *queue,
 {
 	struct virtnet_info *vi = netdev_priv(queue->dev);
 	unsigned int queue_index = get_netdev_rx_queue_index(queue);
-	struct ewma *avg;
+	struct ewma_pkt_len *avg;
 
 	BUG_ON(queue_index >= vi->max_queue_pairs);
 	avg = &vi->rq[queue_index].mrg_avg_pkt_len;
-- 
2.1.4

[PATCH 2/4] ath5k: use DECLARE_EWMA

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

This reduces code size slightly (at least on x86/64) while also
removing memory consumption by two unsigned long values for each
ath5k device.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 drivers/net/wireless/ath/ath5k/Kconfig | 1 -
 drivers/net/wireless/ath/ath5k/ani.c   | 4 ++--
 drivers/net/wireless/ath/ath5k/ath5k.h | 4 +++-
 drivers/net/wireless/ath/ath5k/base.c  | 4 ++--
 drivers/net/wireless/ath/ath5k/debug.c | 2 +-
 5 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/net/wireless/ath/ath5k/Kconfig b/drivers/net/wireless/ath/ath5k/Kconfig
index 2399a3921762..b1278f9f24ba 100644
--- a/drivers/net/wireless/ath/ath5k/Kconfig
+++ b/drivers/net/wireless/ath/ath5k/Kconfig
@@ -5,7 +5,6 @@ config ATH5K
 	select MAC80211_LEDS
 	select LEDS_CLASS
 	select NEW_LEDS
-	select AVERAGE
 	select ATH5K_AHB if ATH25
 	select ATH5K_PCI if !ATH25
 	---help---
diff --git a/drivers/net/wireless/ath/ath5k/ani.c b/drivers/net/wireless/ath/ath5k/ani.c
index 5c008757662b..38be2702c0e2 100644
--- a/drivers/net/wireless/ath/ath5k/ani.c
+++ b/drivers/net/wireless/ath/ath5k/ani.c
@@ -223,7 +223,7 @@ static void
 ath5k_ani_raise_immunity(struct ath5k_hw *ah, struct ath5k_ani_state *as,
 			 bool ofdm_trigger)
 {
-	int rssi = ewma_read(&ah->ah_beacon_rssi_avg);
+	int rssi = ewma_beacon_rssi_read(&ah->ah_beacon_rssi_avg);
 
 	ATH5K_DBG_UNLIMIT(ah, ATH5K_DEBUG_ANI, "raise immunity (%s)",
 		ofdm_trigger ? "ODFM" : "CCK");
@@ -309,7 +309,7 @@ ath5k_ani_raise_immunity(struct ath5k_hw *ah, struct ath5k_ani_state *as,
 static void
 ath5k_ani_lower_immunity(struct ath5k_hw *ah, struct ath5k_ani_state *as)
 {
-	int rssi = ewma_read(&ah->ah_beacon_rssi_avg);
+	int rssi = ewma_beacon_rssi_read(&ah->ah_beacon_rssi_avg);
 
 	ATH5K_DBG_UNLIMIT(ah, ATH5K_DEBUG_ANI, "lower immunity");
 
diff --git a/drivers/net/wireless/ath/ath5k/ath5k.h b/drivers/net/wireless/ath/ath5k/ath5k.h
index e22b0e778927..fa6e89e5c421 100644
--- a/drivers/net/wireless/ath/ath5k/ath5k.h
+++ b/drivers/net/wireless/ath/ath5k/ath5k.h
@@ -1252,6 +1252,8 @@ struct ath5k_statistics {
 #define ATH5K_TXQ_LEN_MAX	(ATH_TXBUF / 4)		/* bufs per queue */
 #define ATH5K_TXQ_LEN_LOW	(ATH5K_TXQ_LEN_MAX / 2)	/* low mark */
 
+DECLARE_EWMA(beacon_rssi, 1024, 8)
+
 /* Driver state associated with an instance of a device */
 struct ath5k_hw {
 	struct ath_common       common;
@@ -1432,7 +1434,7 @@ struct ath5k_hw {
 	struct ath5k_nfcal_hist ah_nfcal_hist;
 
 	/* average beacon RSSI in our BSS (used by ANI) */
-	struct ewma		ah_beacon_rssi_avg;
+	struct ewma_beacon_rssi	ah_beacon_rssi_avg;
 
 	/* noise floor from last periodic calibration */
 	s32			ah_noise_floor;
diff --git a/drivers/net/wireless/ath/ath5k/base.c b/drivers/net/wireless/ath/ath5k/base.c
index 23552f43d125..342563a3706f 100644
--- a/drivers/net/wireless/ath/ath5k/base.c
+++ b/drivers/net/wireless/ath/ath5k/base.c
@@ -1430,7 +1430,7 @@ ath5k_receive_frame(struct ath5k_hw *ah, struct sk_buff *skb,
 	trace_ath5k_rx(ah, skb);
 
 	if (ath_is_mybeacon(common, (struct ieee80211_hdr *)skb->data)) {
-		ewma_add(&ah->ah_beacon_rssi_avg, rs->rs_rssi);
+		ewma_beacon_rssi_add(&ah->ah_beacon_rssi_avg, rs->rs_rssi);
 
 		/* check beacons in IBSS mode */
 		if (ah->opmode == NL80211_IFTYPE_ADHOC)
@@ -2936,7 +2936,7 @@ ath5k_reset(struct ath5k_hw *ah, struct ieee80211_channel *chan,
 	ah->ah_cal_next_short = jiffies +
 		msecs_to_jiffies(ATH5K_TUNE_CALIBRATION_INTERVAL_SHORT);
 
-	ewma_init(&ah->ah_beacon_rssi_avg, 1024, 8);
+	ewma_beacon_rssi_init(&ah->ah_beacon_rssi_avg);
 
 	/* clear survey data and cycle counters */
 	memset(&ah->survey, 0, sizeof(ah->survey));
diff --git a/drivers/net/wireless/ath/ath5k/debug.c b/drivers/net/wireless/ath/ath5k/debug.c
index c70782e8f07b..654a1e33f827 100644
--- a/drivers/net/wireless/ath/ath5k/debug.c
+++ b/drivers/net/wireless/ath/ath5k/debug.c
@@ -722,7 +722,7 @@ static ssize_t read_file_ani(struct file *file, char __user *user_buf,
 			st->mib_intr);
 	len += snprintf(buf + len, sizeof(buf) - len,
 			"beacon RSSI average:\t%d\n",
-			(int)ewma_read(&ah->ah_beacon_rssi_avg));
+			(int)ewma_beacon_rssi_read(&ah->ah_beacon_rssi_avg));
 
 #define CC_PRINT(_struct, _field) \
 	_struct._field, \
-- 
2.1.4

[PATCH 3/4] rt2x00: use DECLARE_EWMA

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

Instead of using the out-of-line EWMA calculation, use DECLARE_EWMA()
to create static inlines. On x86/64 this results in code that's one
byte larger (for me), but reduces struct link_ant and struct link
size by the two unsigned long values that store the parameters each.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 drivers/net/wireless/rt2x00/Kconfig      |  1 -
 drivers/net/wireless/rt2x00/rt2x00.h     |  6 ++++--
 drivers/net/wireless/rt2x00/rt2x00link.c | 18 ++++++------------
 3 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/drivers/net/wireless/rt2x00/Kconfig b/drivers/net/wireless/rt2x00/Kconfig
index 2b4ef256c6b9..de62f5dcb62f 100644
--- a/drivers/net/wireless/rt2x00/Kconfig
+++ b/drivers/net/wireless/rt2x00/Kconfig
@@ -240,7 +240,6 @@ config RT2X00_LIB_USB
 
 config RT2X00_LIB
 	tristate
-	select AVERAGE
 
 config RT2X00_LIB_FIRMWARE
 	bool
diff --git a/drivers/net/wireless/rt2x00/rt2x00.h b/drivers/net/wireless/rt2x00/rt2x00.h
index 9bb398bed9bb..3282ddb766f4 100644
--- a/drivers/net/wireless/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/rt2x00/rt2x00.h
@@ -254,6 +254,8 @@ struct link_qual {
 	int tx_failed;
 };
 
+DECLARE_EWMA(rssi, 1024, 8)
+
 /*
  * Antenna settings about the currently active link.
  */
@@ -285,7 +287,7 @@ struct link_ant {
 	 * Similar to the avg_rssi in the link_qual structure
 	 * this value is updated by using the walking average.
 	 */
-	struct ewma rssi_ant;
+	struct ewma_rssi rssi_ant;
 };
 
 /*
@@ -314,7 +316,7 @@ struct link {
 	/*
 	 * Currently active average RSSI value
 	 */
-	struct ewma avg_rssi;
+	struct ewma_rssi avg_rssi;
 
 	/*
 	 * Work structure for scheduling periodic link tuning.
diff --git a/drivers/net/wireless/rt2x00/rt2x00link.c b/drivers/net/wireless/rt2x00/rt2x00link.c
index 9b941c0c1264..017188e5a736 100644
--- a/drivers/net/wireless/rt2x00/rt2x00link.c
+++ b/drivers/net/wireless/rt2x00/rt2x00link.c
@@ -33,15 +33,11 @@
  */
 #define DEFAULT_RSSI		-128
 
-/* Constants for EWMA calculations. */
-#define RT2X00_EWMA_FACTOR	1024
-#define RT2X00_EWMA_WEIGHT	8
-
-static inline int rt2x00link_get_avg_rssi(struct ewma *ewma)
+static inline int rt2x00link_get_avg_rssi(struct ewma_rssi *ewma)
 {
 	unsigned long avg;
 
-	avg = ewma_read(ewma);
+	avg = ewma_rssi_read(ewma);
 	if (avg)
 		return -avg;
 
@@ -76,8 +72,7 @@ static void rt2x00link_antenna_update_rssi_history(struct rt2x00_dev *rt2x00dev,
 
 static void rt2x00link_antenna_reset(struct rt2x00_dev *rt2x00dev)
 {
-	ewma_init(&rt2x00dev->link.ant.rssi_ant, RT2X00_EWMA_FACTOR,
-		  RT2X00_EWMA_WEIGHT);
+	ewma_rssi_init(&rt2x00dev->link.ant.rssi_ant);
 }
 
 static void rt2x00lib_antenna_diversity_sample(struct rt2x00_dev *rt2x00dev)
@@ -225,12 +220,12 @@ void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
 	/*
 	 * Update global RSSI
 	 */
-	ewma_add(&link->avg_rssi, -rxdesc->rssi);
+	ewma_rssi_add(&link->avg_rssi, -rxdesc->rssi);
 
 	/*
 	 * Update antenna RSSI
 	 */
-	ewma_add(&ant->rssi_ant, -rxdesc->rssi);
+	ewma_rssi_add(&ant->rssi_ant, -rxdesc->rssi);
 }
 
 void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev)
@@ -285,8 +280,7 @@ void rt2x00link_reset_tuner(struct rt2x00_dev *rt2x00dev, bool antenna)
 	 */
 	rt2x00dev->link.count = 0;
 	memset(qual, 0, sizeof(*qual));
-	ewma_init(&rt2x00dev->link.avg_rssi, RT2X00_EWMA_FACTOR,
-		  RT2X00_EWMA_WEIGHT);
+	ewma_rssi_init(&rt2x00dev->link.avg_rssi);
 
 	/*
 	 * Restore the VGC level as stored in the registers,
-- 
2.1.4

[PATCH 3/4] rt2x00: use DECLARE_EWMA

[Johannes Berg]

From: Johannes Berg <johannes.berg-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

Instead of using the out-of-line EWMA calculation, use DECLARE_EWMA()
to create static inlines. On x86/64 this results in code that's one
byte larger (for me), but reduces struct link_ant and struct link
size by the two unsigned long values that store the parameters each.

Signed-off-by: Johannes Berg <johannes.berg-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
 drivers/net/wireless/rt2x00/Kconfig      |  1 -
 drivers/net/wireless/rt2x00/rt2x00.h     |  6 ++++--
 drivers/net/wireless/rt2x00/rt2x00link.c | 18 ++++++------------
 3 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/drivers/net/wireless/rt2x00/Kconfig b/drivers/net/wireless/rt2x00/Kconfig
index 2b4ef256c6b9..de62f5dcb62f 100644
--- a/drivers/net/wireless/rt2x00/Kconfig
+++ b/drivers/net/wireless/rt2x00/Kconfig
@@ -240,7 +240,6 @@ config RT2X00_LIB_USB
 
 config RT2X00_LIB
 	tristate
-	select AVERAGE
 
 config RT2X00_LIB_FIRMWARE
 	bool
diff --git a/drivers/net/wireless/rt2x00/rt2x00.h b/drivers/net/wireless/rt2x00/rt2x00.h
index 9bb398bed9bb..3282ddb766f4 100644
--- a/drivers/net/wireless/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/rt2x00/rt2x00.h
@@ -254,6 +254,8 @@ struct link_qual {
 	int tx_failed;
 };
 
+DECLARE_EWMA(rssi, 1024, 8)
+
 /*
  * Antenna settings about the currently active link.
  */
@@ -285,7 +287,7 @@ struct link_ant {
 	 * Similar to the avg_rssi in the link_qual structure
 	 * this value is updated by using the walking average.
 	 */
-	struct ewma rssi_ant;
+	struct ewma_rssi rssi_ant;
 };
 
 /*
@@ -314,7 +316,7 @@ struct link {
 	/*
 	 * Currently active average RSSI value
 	 */
-	struct ewma avg_rssi;
+	struct ewma_rssi avg_rssi;
 
 	/*
 	 * Work structure for scheduling periodic link tuning.
diff --git a/drivers/net/wireless/rt2x00/rt2x00link.c b/drivers/net/wireless/rt2x00/rt2x00link.c
index 9b941c0c1264..017188e5a736 100644
--- a/drivers/net/wireless/rt2x00/rt2x00link.c
+++ b/drivers/net/wireless/rt2x00/rt2x00link.c
@@ -33,15 +33,11 @@
  */
 #define DEFAULT_RSSI		-128
 
-/* Constants for EWMA calculations. */
-#define RT2X00_EWMA_FACTOR	1024
-#define RT2X00_EWMA_WEIGHT	8
-
-static inline int rt2x00link_get_avg_rssi(struct ewma *ewma)
+static inline int rt2x00link_get_avg_rssi(struct ewma_rssi *ewma)
 {
 	unsigned long avg;
 
-	avg = ewma_read(ewma);
+	avg = ewma_rssi_read(ewma);
 	if (avg)
 		return -avg;
 
@@ -76,8 +72,7 @@ static void rt2x00link_antenna_update_rssi_history(struct rt2x00_dev *rt2x00dev,
 
 static void rt2x00link_antenna_reset(struct rt2x00_dev *rt2x00dev)
 {
-	ewma_init(&rt2x00dev->link.ant.rssi_ant, RT2X00_EWMA_FACTOR,
-		  RT2X00_EWMA_WEIGHT);
+	ewma_rssi_init(&rt2x00dev->link.ant.rssi_ant);
 }
 
 static void rt2x00lib_antenna_diversity_sample(struct rt2x00_dev *rt2x00dev)
@@ -225,12 +220,12 @@ void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
 	/*
 	 * Update global RSSI
 	 */
-	ewma_add(&link->avg_rssi, -rxdesc->rssi);
+	ewma_rssi_add(&link->avg_rssi, -rxdesc->rssi);
 
 	/*
 	 * Update antenna RSSI
 	 */
-	ewma_add(&ant->rssi_ant, -rxdesc->rssi);
+	ewma_rssi_add(&ant->rssi_ant, -rxdesc->rssi);
 }
 
 void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev)
@@ -285,8 +280,7 @@ void rt2x00link_reset_tuner(struct rt2x00_dev *rt2x00dev, bool antenna)
 	 */
 	rt2x00dev->link.count = 0;
 	memset(qual, 0, sizeof(*qual));
-	ewma_init(&rt2x00dev->link.avg_rssi, RT2X00_EWMA_FACTOR,
-		  RT2X00_EWMA_WEIGHT);
+	ewma_rssi_init(&rt2x00dev->link.avg_rssi);
 
 	/*
 	 * Restore the VGC level as stored in the registers,
-- 
2.1.4

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[PATCH 4/4] average: remove out-of-line implementation

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

Since all users are now converted to the inline implementation,
remove the out-of-line implementation entirely.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 include/linux/average.h | 24 -------------------
 lib/Kconfig             | 10 --------
 lib/average.c           | 64 -------------------------------------------------
 3 files changed, 98 deletions(-)
 delete mode 100644 lib/average.c

diff --git a/include/linux/average.h b/include/linux/average.h
index 60f8226c5652..d04aa58280de 100644
--- a/include/linux/average.h
+++ b/include/linux/average.h
@@ -3,30 +3,6 @@
 
 /* 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 avg->internal >> avg->factor;
-}
-
 #define DECLARE_EWMA(name, _factor, _weight)				\
 	struct ewma_##name {						\
 		unsigned long internal;					\
diff --git a/lib/Kconfig b/lib/Kconfig
index 3a2ef67db6c7..278890dd1049 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -460,16 +460,6 @@ config ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 config LRU_CACHE
 	tristate
 
-config AVERAGE
-	bool "Averaging functions"
-	help
-	  This option is provided for the case where no in-kernel-tree
-	  modules require averaging functions, but a module built outside
-	  the kernel tree does. Such modules that use library averaging
-	  functions require Y here.
-
-	  If unsure, say N.
-
 config CLZ_TAB
 	bool
 
diff --git a/lib/average.c b/lib/average.c
deleted file mode 100644
index 114d1beae0c7..000000000000
--- a/lib/average.c
+++ /dev/null
@@ -1,64 +0,0 @@
-/*
- * lib/average.c
- *
- * This source code is licensed under the GNU General Public License,
- * Version 2.  See the file COPYING for more details.
- */
-
-#include <linux/export.h>
-#include <linux/average.h>
-#include <linux/kernel.h>
-#include <linux/bug.h>
-#include <linux/log2.h>
-
-/**
- * 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). 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. 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(!is_power_of_2(weight) || !is_power_of_2(factor));
-
-	avg->weight = ilog2(weight);
-	avg->factor = ilog2(factor);
-	avg->internal = 0;
-}
-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)
-{
-	unsigned long internal = ACCESS_ONCE(avg->internal);
-
-	ACCESS_ONCE(avg->internal) = internal ?
-		(((internal << avg->weight) - internal) +
-			(val << avg->factor)) >> avg->weight :
-		(val << avg->factor);
-	return avg;
-}
-EXPORT_SYMBOL(ewma_add);
-- 
2.1.4

Re: [PATCH 1/4] virtio_net: use DECLARE_EWMA

[Johannes Berg]

Sorry, forgot to Cc Michael and the virt list - patch reproduced below
in full.

johannes

>From 22500fbcf722748fe3471b2e4c6156db47aade15 Mon Sep 17 00:00:00 2001
From: Johannes Berg <johannes.berg@intel.com>
Date: Wed, 19 Aug 2015 09:25:18 +0200
Subject: [PATCH] virtio_net: use DECLARE_EWMA

Instead of using the out-of-line EWMA calculation, use DECLARE_EWMA()
to create static inlines. On x86/64 this results in no change in code
size for me, but reduces the struct receive_queue size by the two
unsigned long values that store the parameters.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 drivers/net/Kconfig      |  1 -
 drivers/net/virtio_net.c | 22 +++++++++++-----------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index e58468b02987..f50373645ab4 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -282,7 +282,6 @@ config VETH
 config VIRTIO_NET
 	tristate "Virtio network driver"
 	depends on VIRTIO
-	select AVERAGE
 	---help---
 	  This is the virtual network driver for virtio.  It can be used with
 	  lguest or QEMU based VMMs (like KVM or Xen).  Say Y or M.
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 546b669fbfdd..9b950f2db836 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -40,12 +40,12 @@ module_param(gso, bool, 0444);
 #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
 #define GOOD_COPY_LEN	128
 
-/* Weight used for the RX packet size EWMA. The average packet size is used to
- * determine the packet buffer size when refilling RX rings. As the entire RX
- * ring may be refilled at once, the weight is chosen so that the EWMA will be
- * insensitive to short-term, transient changes in packet size.
+/* RX packet size EWMA. The average packet size is used to determine the packet
+ * buffer size when refilling RX rings. As the entire RX ring may be refilled
+ * at once, the weight is chosen so that the EWMA will be insensitive to short-
+ * term, transient changes in packet size.
  */
-#define RECEIVE_AVG_WEIGHT 64
+DECLARE_EWMA(pkt_len, 1, 64)
 
 /* Minimum alignment for mergeable packet buffers. */
 #define MERGEABLE_BUFFER_ALIGN max(L1_CACHE_BYTES, 256)
@@ -85,7 +85,7 @@ struct receive_queue {
 	struct page *pages;
 
 	/* Average packet length for mergeable receive buffers. */
-	struct ewma mrg_avg_pkt_len;
+	struct ewma_pkt_len mrg_avg_pkt_len;
 
 	/* Page frag for packet buffer allocation. */
 	struct page_frag alloc_frag;
@@ -407,7 +407,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		}
 	}
 
-	ewma_add(&rq->mrg_avg_pkt_len, head_skb->len);
+	ewma_pkt_len_add(&rq->mrg_avg_pkt_len, head_skb->len);
 	return head_skb;
 
 err_skb:
@@ -600,12 +600,12 @@ static int add_recvbuf_big(struct virtnet_info *vi, struct receive_queue *rq,
 	return err;
 }
 
-static unsigned int get_mergeable_buf_len(struct ewma *avg_pkt_len)
+static unsigned int get_mergeable_buf_len(struct ewma_pkt_len *avg_pkt_len)
 {
 	const size_t hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
 	unsigned int len;
 
-	len = hdr_len + clamp_t(unsigned int, ewma_read(avg_pkt_len),
+	len = hdr_len + clamp_t(unsigned int, ewma_pkt_len_read(avg_pkt_len),
 			GOOD_PACKET_LEN, PAGE_SIZE - hdr_len);
 	return ALIGN(len, MERGEABLE_BUFFER_ALIGN);
 }
@@ -1615,7 +1615,7 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
 		napi_hash_add(&vi->rq[i].napi);
 
 		sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg));
-		ewma_init(&vi->rq[i].mrg_avg_pkt_len, 1, RECEIVE_AVG_WEIGHT);
+		ewma_pkt_len_init(&vi->rq[i].mrg_avg_pkt_len);
 		sg_init_table(vi->sq[i].sg, ARRAY_SIZE(vi->sq[i].sg));
 	}
 
@@ -1658,7 +1658,7 @@ static ssize_t mergeable_rx_buffer_size_show(struct netdev_rx_queue *queue,
 {
 	struct virtnet_info *vi = netdev_priv(queue->dev);
 	unsigned int queue_index = get_netdev_rx_queue_index(queue);
-	struct ewma *avg;
+	struct ewma_pkt_len *avg;
 
 	BUG_ON(queue_index >= vi->max_queue_pairs);
 	avg = &vi->rq[queue_index].mrg_avg_pkt_len;

Re: [PATCH 1/4] virtio_net: use DECLARE_EWMA

[Johannes Berg]

Sorry, forgot to Cc Michael and the virt list - patch reproduced below
in full.

johannes

From 22500fbcf722748fe3471b2e4c6156db47aade15 Mon Sep 17 00:00:00 2001
From: Johannes Berg <johannes.berg@intel.com>
Date: Wed, 19 Aug 2015 09:25:18 +0200
Subject: [PATCH] virtio_net: use DECLARE_EWMA

Instead of using the out-of-line EWMA calculation, use DECLARE_EWMA()
to create static inlines. On x86/64 this results in no change in code
size for me, but reduces the struct receive_queue size by the two
unsigned long values that store the parameters.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 drivers/net/Kconfig      |  1 -
 drivers/net/virtio_net.c | 22 +++++++++++-----------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index e58468b02987..f50373645ab4 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -282,7 +282,6 @@ config VETH
 config VIRTIO_NET
 	tristate "Virtio network driver"
 	depends on VIRTIO
-	select AVERAGE
 	---help---
 	  This is the virtual network driver for virtio.  It can be used with
 	  lguest or QEMU based VMMs (like KVM or Xen).  Say Y or M.
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 546b669fbfdd..9b950f2db836 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -40,12 +40,12 @@ module_param(gso, bool, 0444);
 #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
 #define GOOD_COPY_LEN	128
 
-/* Weight used for the RX packet size EWMA. The average packet size is used to
- * determine the packet buffer size when refilling RX rings. As the entire RX
- * ring may be refilled at once, the weight is chosen so that the EWMA will be
- * insensitive to short-term, transient changes in packet size.
+/* RX packet size EWMA. The average packet size is used to determine the packet
+ * buffer size when refilling RX rings. As the entire RX ring may be refilled
+ * at once, the weight is chosen so that the EWMA will be insensitive to short-
+ * term, transient changes in packet size.
  */
-#define RECEIVE_AVG_WEIGHT 64
+DECLARE_EWMA(pkt_len, 1, 64)
 
 /* Minimum alignment for mergeable packet buffers. */
 #define MERGEABLE_BUFFER_ALIGN max(L1_CACHE_BYTES, 256)
@@ -85,7 +85,7 @@ struct receive_queue {
 	struct page *pages;
 
 	/* Average packet length for mergeable receive buffers. */
-	struct ewma mrg_avg_pkt_len;
+	struct ewma_pkt_len mrg_avg_pkt_len;
 
 	/* Page frag for packet buffer allocation. */
 	struct page_frag alloc_frag;
@@ -407,7 +407,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		}
 	}
 
-	ewma_add(&rq->mrg_avg_pkt_len, head_skb->len);
+	ewma_pkt_len_add(&rq->mrg_avg_pkt_len, head_skb->len);
 	return head_skb;
 
 err_skb:
@@ -600,12 +600,12 @@ static int add_recvbuf_big(struct virtnet_info *vi, struct receive_queue *rq,
 	return err;
 }
 
-static unsigned int get_mergeable_buf_len(struct ewma *avg_pkt_len)
+static unsigned int get_mergeable_buf_len(struct ewma_pkt_len *avg_pkt_len)
 {
 	const size_t hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
 	unsigned int len;
 
-	len = hdr_len + clamp_t(unsigned int, ewma_read(avg_pkt_len),
+	len = hdr_len + clamp_t(unsigned int, ewma_pkt_len_read(avg_pkt_len),
 			GOOD_PACKET_LEN, PAGE_SIZE - hdr_len);
 	return ALIGN(len, MERGEABLE_BUFFER_ALIGN);
 }
@@ -1615,7 +1615,7 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
 		napi_hash_add(&vi->rq[i].napi);
 
 		sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg));
-		ewma_init(&vi->rq[i].mrg_avg_pkt_len, 1, RECEIVE_AVG_WEIGHT);
+		ewma_pkt_len_init(&vi->rq[i].mrg_avg_pkt_len);
 		sg_init_table(vi->sq[i].sg, ARRAY_SIZE(vi->sq[i].sg));
 	}
 
@@ -1658,7 +1658,7 @@ static ssize_t mergeable_rx_buffer_size_show(struct netdev_rx_queue *queue,
 {
 	struct virtnet_info *vi = netdev_priv(queue->dev);
 	unsigned int queue_index = get_netdev_rx_queue_index(queue);
-	struct ewma *avg;
+	struct ewma_pkt_len *avg;
 
 	BUG_ON(queue_index >= vi->max_queue_pairs);
 	avg = &vi->rq[queue_index].mrg_avg_pkt_len;

Re: [PATCH 0/4] average: convert users to inline implementation

[David Miller]

From: Johannes Berg <johannes@sipsolutions.net>
Date: Wed, 19 Aug 2015 09:46:18 +0200

> Since there's very little benefit of the out-of-line implementation
> (a single byte of .text in one driver as far as I've seen), convert
> all drivers to the inline implementation, saving memory, and remove
> the out-of-line implementation.
> 
> Perhaps the easiest would be for Dave to take all of these patches?

Ok, I'll applied this series to net-next, thanks.