2004-10-01 11:15:25

by Oleg Nesterov

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

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 <[email protected]>

--- 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;

2004-10-02 13:05:20

by Kirill Korotaev

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

I can sign off both patches. They look ok.

Signed-off-By: Kirill Korotaev <[email protected]>

> 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