[PATCH 1/2] detach_pid(): restore optimization

[PATCH 1/2] detach_pid(): restore optimization

[Oleg Nesterov]

Hello.

Kirill's kernel/pid.c rework broke optimization logic in detach_pid().
Non zero return from __detach_pid() was used to indicate, that this pid
can probably be freed. Current version always (modulo idle threads)
return non zero value, thus resulting in unneccesary pid_hash scanning.

Also, uninlining __detach_pid() reduces pid.o text size from 2492 to 1600
bytes.

Oleg.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

--- 2.6.9-rc3/kernel/pid.c~	Thu Sep 30 15:05:25 2004
+++ 2.6.9-rc3/kernel/pid.c	Fri Oct  1 11:26:11 2004
@@ -178,15 +178,18 @@ int fastcall attach_pid(task_t *task, en
 	return 0;
 }
 
-static inline int __detach_pid(task_t *task, enum pid_type type)
+static fastcall int __detach_pid(task_t *task, enum pid_type type)
 {
 	struct pid *pid, *pid_next;
-	int nr;
+	int nr = 0;
 
 	pid = &task->pids[type];
 	if (!hlist_unhashed(&pid->pid_chain)) {
 		hlist_del(&pid->pid_chain);
-		if (!list_empty(&pid->pid_list)) {
+
+		if (list_empty(&pid->pid_list))
+			nr = pid->nr;
+		else {
 			pid_next = list_entry(pid->pid_list.next,
 						struct pid, pid_list);
 			/* insert next pid from pid_list to hash */
@@ -194,8 +197,8 @@ static inline int __detach_pid(task_t *t
 				&pid_hash[type][pid_hashfn(pid_next->nr)]);
 		}
 	}
+
 	list_del(&pid->pid_list);
-	nr = pid->nr;
 	pid->nr = 0;
 
 	return nr;

Re: [PATCH 1/2] detach_pid(): restore optimization

[Kirill Korotaev]

I can sign off both patches. They look ok.

Signed-off-By: Kirill Korotaev <dev@sw.ru>

> Kirill's kernel/pid.c rework broke optimization logic in detach_pid().
> Non zero return from __detach_pid() was used to indicate, that this pid
> can probably be freed. Current version always (modulo idle threads)
> return non zero value, thus resulting in unneccesary pid_hash scanning.
> 
> Also, uninlining __detach_pid() reduces pid.o text size from 2492 to 1600
> bytes.
> 
> Oleg.

[...]

Kirill