Performance improvements with scalable statistics counters

diff -ruN linux-2.5.5/include/linux/pcpu_alloc.h statctr-2.5.5/include/linux/pcpu_alloc.h
@@ -0,0 +1,75 @@
+/*
+ * Per-CPU Word allocator.
+ *
+ * Inspired by the freelist maintanance of the slab allocator implementation
+ *  (in mm/slab.c)
+ *
+ * Copyright (c) International Business Machines Corp., 2001
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Author:              Ravikiran Thirumalai <[email protected]>
+ *
+ * include/linux/pcpu_alloc.h
+ *
+ */
+#ifndef _LINUX_PCPU_ALLOC_H
+#define _LINUX_PCPU_ALLOC_H
+ 
+#ifdef __KERNEL__
+
+#include <linux/config.h>
+#include <linux/init.h>
+#include <linux/threads.h>
+#include <linux/sched.h>
+
+/* Prototypes */
+#ifdef	CONFIG_SMP
+
+typedef struct pcpu_ctr_s {
+	void *arr[NR_CPUS];	/* Pcpu counter array */
+	void *blkp;		/* Pointer to block from which ctr was 
+				   allocated from (for use with free code) */
+} pcpu_ctr_t;
+
+extern pcpu_ctr_t *pcpu_ctr_alloc(int);
+extern void pcpu_ctr_free(pcpu_ctr_t *);
+extern void __init pcpu_ctr_sys_init(void);
+
+#define PCPU_CTR(ctr, cpuid) ((unsigned long *)ctr->arr[cpuid])
+
+#else	/* CONFIG_SMP */
+
+#include <linux/slab.h>
+
+typedef unsigned long pcpu_ctr_t;
+
+static inline pcpu_ctr_t *pcpu_ctr_alloc(int flags) 
+{
+	return(kmalloc(sizeof(pcpu_ctr_t), flags));
+}
+
+static inline void pcpu_ctr_free(pcpu_ctr_t *ptr)
+{
+	kfree(ptr);
+}
+
+#define pcpu_ctr_sys_init() do { } while (0)    
+
+#endif  /* CONFIG_SMP */
+ 
+#endif  /* __KERNEL__ */
+ 
+#endif  /* _LINUX_PCPU_ALLOC_H */

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diff -ruN linux-2.5.5/init/main.c statctr-2.5.5/init/main.c
@@ -27,6 +27,7 @@
 #include <linux/iobuf.h>
 #include <linux/bootmem.h>
 #include <linux/tty.h>
+#include <linux/pcpu_alloc.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>

@@ -383,6 +384,7 @@
 	 *	make syscalls (and thus be locked).
 	 */
 	smp_init();
+	pcpu_ctr_sys_init();
 
 	/* Do the rest non-__init'ed, we're now alive */
 	rest_init();

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diff -ruN linux-2.5.5/drivers/net/loopback.c statctrusagelo/drivers/net/loopback.c
@@ -87,10 +87,10 @@
 #endif
 
 	dev->last_rx = jiffies;
-	stats->rx_bytes+=skb->len;
-	stats->tx_bytes+=skb->len;
-	stats->rx_packets++;
-	stats->tx_packets++;
+	statctr_add(&stats->rx_bytes, skb->len);
+	statctr_add(&stats->tx_bytes, skb->len);
+	statctr_inc(&stats->rx_packets);
+	statctr_inc(&stats->tx_packets);
 
 	netif_rx(skb);
 

@@ -120,7 +120,11 @@
 	dev->priv = kmalloc(sizeof(struct net_device_stats), GFP_KERNEL);
 	if (dev->priv == NULL)
 			return -ENOMEM;
-	memset(dev->priv, 0, sizeof(struct net_device_stats));
+	if (statctr_ninit((statctr_t *)dev->priv, 0, 23)) {
+		/* Init failed cleanup.. */
+		kfree(dev->priv);
+		return -ENOMEM;
+	}
 	dev->get_stats = get_stats;
 
 	/*

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diff -ruN linux-2.5.5/net/core/dev.c statctrusagelo/net/core/dev.c
@@ -1691,19 +1691,19 @@
 	if (stats)
 		size = sprintf(buffer, "%6s:%8lu %7lu %4lu %4lu %4lu %5lu %10lu %9lu %8lu %7lu %4lu %4lu %4lu %5lu %7lu %10lu\n",
  		   dev->name,
-		   stats->rx_bytes,
-		   stats->rx_packets, stats->rx_errors,
-		   stats->rx_dropped + stats->rx_missed_errors,
-		   stats->rx_fifo_errors,
-		   stats->rx_length_errors + stats->rx_over_errors
-		   + stats->rx_crc_errors + stats->rx_frame_errors,
-		   stats->rx_compressed, stats->multicast,
-		   stats->tx_bytes,
-		   stats->tx_packets, stats->tx_errors, stats->tx_dropped,
-		   stats->tx_fifo_errors, stats->collisions,
-		   stats->tx_carrier_errors + stats->tx_aborted_errors
-		   + stats->tx_window_errors + stats->tx_heartbeat_errors,
-		   stats->tx_compressed);
+		   statctr_read(&stats->rx_bytes),
+		   statctr_read(&stats->rx_packets), statctr_read(&stats->rx_errors),
+		   statctr_read(&stats->rx_dropped) + statctr_read(&stats->rx_missed_errors),
+		   statctr_read(&stats->rx_fifo_errors),
+		   statctr_read(&stats->rx_length_errors) + statctr_read(&stats->rx_over_errors)
+		   + statctr_read(&stats->rx_crc_errors) + statctr_read(&stats->rx_frame_errors),
+		   statctr_read(&stats->rx_compressed), statctr_read(&stats->multicast),
+		   statctr_read(&stats->tx_bytes),
+		   statctr_read(&stats->tx_packets), statctr_read(&stats->tx_errors), statctr_read(&stats->tx_dropped),
+		   statctr_read(&stats->tx_fifo_errors), statctr_read(&stats->collisions),
+		   statctr_read(&stats->tx_carrier_errors) + statctr_read(&stats->tx_aborted_errors)
+		   + statctr_read(&stats->tx_window_errors) + statctr_read(&stats->tx_heartbeat_errors),
+		   statctr_read(&stats->tx_compressed));
 	else
 		size = sprintf(buffer, "%6s: No statistics available.\n", dev->name);