lkml.org 
[lkml]   [2002]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[pidhash] [3/4] eliminate proc_fill_super() tasklist iteration
Introduce a per-cpu counter for the number of processes on the system,
and use that to set ->i_nlink in proc_fill_super() in constant time.

fs/proc/inode.c | 6 +-----
include/linux/sched.h | 3 +++
kernel/exit.c | 2 ++
kernel/fork.c | 14 ++++++++++++++
4 files changed, 20 insertions(+), 5 deletions(-)

diff -urpN mm1-2.5.50-2/fs/proc/inode.c wli-2.5.50-3/fs/proc/inode.c
--- mm1-2.5.50-2/fs/proc/inode.c 2002-11-27 14:36:19.000000000 -0800
+++ wli-2.5.50-3/fs/proc/inode.c 2002-12-04 18:40:59.000000000 -0800
@@ -234,11 +234,7 @@ int proc_fill_super(struct super_block *
/*
* Fixup the root inode's nlink value
*/
- read_lock(&tasklist_lock);
- for_each_process(p)
- if (p->pid)
- root_inode->i_nlink++;
- read_unlock(&tasklist_lock);
+ root_inode->i_nlink += nr_processes();
s->s_root = d_alloc_root(root_inode);
if (!s->s_root)
goto out_no_root;
diff -urpN mm1-2.5.50-2/include/linux/sched.h wli-2.5.50-3/include/linux/sched.h
--- mm1-2.5.50-2/include/linux/sched.h 2002-12-04 12:49:47.000000000 -0800
+++ wli-2.5.50-3/include/linux/sched.h 2002-12-04 18:42:39.000000000 -0800
@@ -27,6 +27,7 @@
#include <linux/compiler.h>
#include <linux/completion.h>
#include <linux/pid.h>
+#include <linux/percpu.h>

struct exec_domain;

@@ -87,6 +88,8 @@ extern unsigned long avenrun[]; /* Load

extern int nr_threads;
extern int last_pid;
+DECLARE_PER_CPU(unsigned long, process_counts);
+extern int nr_processes(void);
extern unsigned long nr_running(void);
extern unsigned long nr_uninterruptible(void);
extern unsigned long nr_iowait(void);
diff -urpN mm1-2.5.50-2/kernel/exit.c wli-2.5.50-3/kernel/exit.c
--- mm1-2.5.50-2/kernel/exit.c 2002-12-04 12:49:47.000000000 -0800
+++ wli-2.5.50-3/kernel/exit.c 2002-12-04 18:57:08.000000000 -0800
@@ -41,6 +41,8 @@ static struct dentry * __unhash_process(
if (thread_group_leader(p)) {
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
+ if (p->pid)
+ per_cpu(process_counts, smp_processor_id())--;
}

REMOVE_LINKS(p);
diff -urpN mm1-2.5.50-2/kernel/fork.c wli-2.5.50-3/kernel/fork.c
--- mm1-2.5.50-2/kernel/fork.c 2002-12-04 12:49:47.000000000 -0800
+++ wli-2.5.50-3/kernel/fork.c 2002-12-04 18:56:55.000000000 -0800
@@ -48,6 +48,8 @@ int nr_threads;
int max_threads;
unsigned long total_forks; /* Handle normal Linux uptimes. */

+DEFINE_PER_CPU(unsigned long, process_counts);
+
rwlock_t tasklist_lock __cacheline_aligned = RW_LOCK_UNLOCKED; /* outer */

/*
@@ -57,6 +59,16 @@ rwlock_t tasklist_lock __cacheline_align
*/
static task_t *task_cache[NR_CPUS] __cacheline_aligned;

+int nr_processes(void)
+{
+ int cpu;
+ unsigned long total = 0;
+
+ for (cpu = 0; cpu < NR_CPUS; ++cpu)
+ total += per_cpu(process_counts, cpu);
+ return (int)total;
+}
+
void __put_task_struct(struct task_struct *tsk)
{
if (tsk != current) {
@@ -934,6 +946,8 @@ static struct task_struct *copy_process(
attach_pid(p, PIDTYPE_TGID, p->tgid);
attach_pid(p, PIDTYPE_PGID, p->pgrp);
attach_pid(p, PIDTYPE_SID, p->session);
+ if (p->pid)
+ per_cpu(process_counts, smp_processor_id())++;
} else
link_pid(p, p->pids + PIDTYPE_TGID, &p->group_leader->pids[PIDTYPE_TGID].pid);

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2005-03-22 13:31    [from the cache]
©2003-2011 Jasper Spaans