From ba8e8755393fd032e448b3cfa35cb01743807699 Mon Sep 17 00:00:00 2001
From: Andrew Morton <akpm@digeo.com>
Date: Sat, 12 Apr 2003 12:59:51 -0700
Subject: [PATCH] percpu_counters: approximate but scalable counters

Several places in ext2 and ext3 are using filesystem-wide counters which use
global locking.  Mainly for the orlov allocator's heuristics.

To solve the contention which this causes we can trade off accuracy against
speed.

This patch introduces a "percpu_counter" library type in which the counts are
per-cpu and are periodically spilled into a global counter.  Readers only
read the global counter.

These objects are *large*.  On a 32 CPU P4, they are 4 kbytes.  On a 4 way
p3, 128 bytes.
---
 kernel/ksyms.c | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'kernel')

diff --git a/kernel/ksyms.c b/kernel/ksyms.c
index f7ef45020896..5d31affa36ce 100644
--- a/kernel/ksyms.c
+++ b/kernel/ksyms.c
@@ -58,6 +58,7 @@
 #include <linux/ptrace.h>
 #include <linux/time.h>
 #include <linux/backing-dev.h>
+#include <linux/percpu_counter.h>
 #include <asm/checksum.h>
 
 #if defined(CONFIG_PROC_FS)
@@ -100,6 +101,7 @@ EXPORT_SYMBOL(kfree);
 #ifdef CONFIG_SMP
 EXPORT_SYMBOL(kmalloc_percpu);
 EXPORT_SYMBOL(kfree_percpu);
+EXPORT_SYMBOL(percpu_counter_mod);
 #endif
 EXPORT_SYMBOL(vfree);
 EXPORT_SYMBOL(__vmalloc);
-- 
cgit v1.2.3