Re: [PATCH -mm] scheduler: fix the return of the first time_slice
At Mon, 16 Apr 2007 14:45:59 +0400,
Oleg Nesterov wrote:
>
> On 04/16, Satoru Takeuchi wrote:
> >
> > --- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/exit.c 2007-04-15
> > 16:56:12.0 +0900
> > +++ linux-2.6.21-rc6-mm1.tsfix/kernel/exit.c2007-04-15
> > 16:56:17.0 +0900
> > @@ -680,10 +680,14 @@
> > reaper = child_reaper(father);
> > break;
> > }
> > + if (reaper->time_slice_reaper == father)
> > + reaper->time_slice_reaper = NULL;
> > } while (reaper->exit_state);
> >
> > list_for_each_safe(_p, _n, >children) {
> > p = list_entry(_p, struct task_struct, sibling);
> > + if (p->time_slice_reaper == father)
> > + p->time_slice_reaper = NULL;
> > choose_new_parent(p, reaper);
> > reparent_thread(p, father);
> > }
> > Index: linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c
> > ===
> > --- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/sched.c 2007-04-15
> > 16:56:12.0 +0900
> > +++ linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c 2007-04-15
> > 16:56:17.0 +0900
> > @@ -1693,7 +1693,7 @@
> > * The remainder of the first timeslice might be recovered by
> > * the parent if the child exits early enough.
> > */
> > - p->first_time_slice = 1;
> > + p->time_slice_reaper = current;
> > p->timestamp = sched_clock();
> > local_irq_enable();
>
> I am afraid this doesn't work for CLONE_THREAD. Suppose that some sub-thread
> (not
> main thread) T1 creates another sub-thread, T2.
>
> T2->time_slice_reaper = T1.
>
> then T1 exits, but forget_original_parent(T1) doesn't change
> T2->time_slice_reaper,
> because T2 is not on T1->children list. Now T2->time_slice_reaper points to an
> already freed task_struct.
I intended that CLONE_THREAD case is managed on the do-while loop seeking
`reaper'.
However, anyway, my patch has a bug. On T1 exiting, if there are any living
threads
ahead of T2, T2->time_slice_reaper isn't checked. What a easy mistake ... sorry.
I'll post fixed version soon.
Satoru
-
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Re: [PATCH -mm] scheduler: fix the return of the first time_slice
* Oleg Nesterov <[EMAIL PROTECTED]> wrote: > > >* The remainder of the first timeslice might be recovered by > > >* the parent if the child exits early enough. > > >*/ > > > - p->first_time_slice = 1; > > > + p->time_slice_reaper = current; > > > p->timestamp = sched_clock(); > > > local_irq_enable(); > > > > I am afraid this doesn't work for CLONE_THREAD. Suppose that some > > sub-thread (not main thread) T1 creates another sub-thread, T2. > In case I was not clear... > To make this correct, we should iterate over all thread-group, but > this can slow down exit() when we have a lot of threads. > > I guess we need Ingo's opinion on that. right now my first cautious estimation seems to be that we might be able to get rid of this whole child/parent timeslice sharing complexity and do all the scheduling setup without affecting the parent - hence avoiding all the reaper problems as well. People reported interactivity improvements with this removed from CFS. (It all still needs a ton of validation to make sure, but the trend seems to be this.) (the only valid component of that complexity is 'child runs first' - but it's not really related to the timesplice splitting thing just intermixed with it.) Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH -mm] scheduler: fix the return of the first time_slice
On 04/16, Oleg Nesterov wrote:
>
> On 04/16, Satoru Takeuchi wrote:
> >
> > --- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/exit.c 2007-04-15
> > 16:56:12.0 +0900
> > +++ linux-2.6.21-rc6-mm1.tsfix/kernel/exit.c2007-04-15
> > 16:56:17.0 +0900
> > @@ -680,10 +680,14 @@
> > reaper = child_reaper(father);
> > break;
> > }
> > + if (reaper->time_slice_reaper == father)
> > + reaper->time_slice_reaper = NULL;
> > } while (reaper->exit_state);
> >
> > list_for_each_safe(_p, _n, >children) {
> > p = list_entry(_p, struct task_struct, sibling);
> > + if (p->time_slice_reaper == father)
> > + p->time_slice_reaper = NULL;
> > choose_new_parent(p, reaper);
> > reparent_thread(p, father);
> > }
> > Index: linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c
> > ===
> > --- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/sched.c 2007-04-15
> > 16:56:12.0 +0900
> > +++ linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c 2007-04-15
> > 16:56:17.0 +0900
> > @@ -1693,7 +1693,7 @@
> > * The remainder of the first timeslice might be recovered by
> > * the parent if the child exits early enough.
> > */
> > - p->first_time_slice = 1;
> > + p->time_slice_reaper = current;
> > p->timestamp = sched_clock();
> > local_irq_enable();
>
> I am afraid this doesn't work for CLONE_THREAD. Suppose that some sub-thread
> (not
> main thread) T1 creates another sub-thread, T2.
>
> T2->time_slice_reaper = T1.
>
> then T1 exits, but forget_original_parent(T1) doesn't change
> T2->time_slice_reaper,
> because T2 is not on T1->children list. Now T2->time_slice_reaper points to an
> already freed task_struct.
In case I was not clear...
Note that "do {} while ()" loop in forget_original_parent() stops when it finds
a sub-thread with ->exit_state == 0. This means we can miss another sub-thread
which has ->time_slice_reaper == father.
To make this correct, we should iterate over all thread-group, but this can slow
down exit() when we have a lot of threads.
I guess we need Ingo's opinion on that.
Oleg.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH -mm] scheduler: fix the return of the first time_slice
On 04/16, Satoru Takeuchi wrote:
>
> --- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/exit.c 2007-04-15
> 16:56:12.0 +0900
> +++ linux-2.6.21-rc6-mm1.tsfix/kernel/exit.c 2007-04-15 16:56:17.0
> +0900
> @@ -680,10 +680,14 @@
> reaper = child_reaper(father);
> break;
> }
> + if (reaper->time_slice_reaper == father)
> + reaper->time_slice_reaper = NULL;
> } while (reaper->exit_state);
>
> list_for_each_safe(_p, _n, >children) {
> p = list_entry(_p, struct task_struct, sibling);
> + if (p->time_slice_reaper == father)
> + p->time_slice_reaper = NULL;
> choose_new_parent(p, reaper);
> reparent_thread(p, father);
> }
> Index: linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c
> ===
> --- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/sched.c2007-04-15
> 16:56:12.0 +0900
> +++ linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c 2007-04-15 16:56:17.0
> +0900
> @@ -1693,7 +1693,7 @@
>* The remainder of the first timeslice might be recovered by
>* the parent if the child exits early enough.
>*/
> - p->first_time_slice = 1;
> + p->time_slice_reaper = current;
> p->timestamp = sched_clock();
> local_irq_enable();
I am afraid this doesn't work for CLONE_THREAD. Suppose that some sub-thread
(not
main thread) T1 creates another sub-thread, T2.
T2->time_slice_reaper = T1.
then T1 exits, but forget_original_parent(T1) doesn't change
T2->time_slice_reaper,
because T2 is not on T1->children list. Now T2->time_slice_reaper points to an
already freed task_struct.
Oleg.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH -mm] scheduler: fix the return of the first time_slice
On 04/16, Satoru Takeuchi wrote:
--- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/exit.c 2007-04-15
16:56:12.0 +0900
+++ linux-2.6.21-rc6-mm1.tsfix/kernel/exit.c 2007-04-15 16:56:17.0
+0900
@@ -680,10 +680,14 @@
reaper = child_reaper(father);
break;
}
+ if (reaper-time_slice_reaper == father)
+ reaper-time_slice_reaper = NULL;
} while (reaper-exit_state);
list_for_each_safe(_p, _n, father-children) {
p = list_entry(_p, struct task_struct, sibling);
+ if (p-time_slice_reaper == father)
+ p-time_slice_reaper = NULL;
choose_new_parent(p, reaper);
reparent_thread(p, father);
}
Index: linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c
===
--- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/sched.c2007-04-15
16:56:12.0 +0900
+++ linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c 2007-04-15 16:56:17.0
+0900
@@ -1693,7 +1693,7 @@
* The remainder of the first timeslice might be recovered by
* the parent if the child exits early enough.
*/
- p-first_time_slice = 1;
+ p-time_slice_reaper = current;
p-timestamp = sched_clock();
local_irq_enable();
I am afraid this doesn't work for CLONE_THREAD. Suppose that some sub-thread
(not
main thread) T1 creates another sub-thread, T2.
T2-time_slice_reaper = T1.
then T1 exits, but forget_original_parent(T1) doesn't change
T2-time_slice_reaper,
because T2 is not on T1-children list. Now T2-time_slice_reaper points to an
already freed task_struct.
Oleg.
-
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH -mm] scheduler: fix the return of the first time_slice
On 04/16, Oleg Nesterov wrote:
On 04/16, Satoru Takeuchi wrote:
--- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/exit.c 2007-04-15
16:56:12.0 +0900
+++ linux-2.6.21-rc6-mm1.tsfix/kernel/exit.c2007-04-15
16:56:17.0 +0900
@@ -680,10 +680,14 @@
reaper = child_reaper(father);
break;
}
+ if (reaper-time_slice_reaper == father)
+ reaper-time_slice_reaper = NULL;
} while (reaper-exit_state);
list_for_each_safe(_p, _n, father-children) {
p = list_entry(_p, struct task_struct, sibling);
+ if (p-time_slice_reaper == father)
+ p-time_slice_reaper = NULL;
choose_new_parent(p, reaper);
reparent_thread(p, father);
}
Index: linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c
===
--- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/sched.c 2007-04-15
16:56:12.0 +0900
+++ linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c 2007-04-15
16:56:17.0 +0900
@@ -1693,7 +1693,7 @@
* The remainder of the first timeslice might be recovered by
* the parent if the child exits early enough.
*/
- p-first_time_slice = 1;
+ p-time_slice_reaper = current;
p-timestamp = sched_clock();
local_irq_enable();
I am afraid this doesn't work for CLONE_THREAD. Suppose that some sub-thread
(not
main thread) T1 creates another sub-thread, T2.
T2-time_slice_reaper = T1.
then T1 exits, but forget_original_parent(T1) doesn't change
T2-time_slice_reaper,
because T2 is not on T1-children list. Now T2-time_slice_reaper points to an
already freed task_struct.
In case I was not clear...
Note that do {} while () loop in forget_original_parent() stops when it finds
a sub-thread with -exit_state == 0. This means we can miss another sub-thread
which has -time_slice_reaper == father.
To make this correct, we should iterate over all thread-group, but this can slow
down exit() when we have a lot of threads.
I guess we need Ingo's opinion on that.
Oleg.
-
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH -mm] scheduler: fix the return of the first time_slice
* Oleg Nesterov [EMAIL PROTECTED] wrote: * The remainder of the first timeslice might be recovered by * the parent if the child exits early enough. */ - p-first_time_slice = 1; + p-time_slice_reaper = current; p-timestamp = sched_clock(); local_irq_enable(); I am afraid this doesn't work for CLONE_THREAD. Suppose that some sub-thread (not main thread) T1 creates another sub-thread, T2. In case I was not clear... To make this correct, we should iterate over all thread-group, but this can slow down exit() when we have a lot of threads. I guess we need Ingo's opinion on that. right now my first cautious estimation seems to be that we might be able to get rid of this whole child/parent timeslice sharing complexity and do all the scheduling setup without affecting the parent - hence avoiding all the reaper problems as well. People reported interactivity improvements with this removed from CFS. (It all still needs a ton of validation to make sure, but the trend seems to be this.) (the only valid component of that complexity is 'child runs first' - but it's not really related to the timesplice splitting thing just intermixed with it.) Ingo - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH -mm] scheduler: fix the return of the first time_slice
At Mon, 16 Apr 2007 14:45:59 +0400,
Oleg Nesterov wrote:
On 04/16, Satoru Takeuchi wrote:
--- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/exit.c 2007-04-15
16:56:12.0 +0900
+++ linux-2.6.21-rc6-mm1.tsfix/kernel/exit.c2007-04-15
16:56:17.0 +0900
@@ -680,10 +680,14 @@
reaper = child_reaper(father);
break;
}
+ if (reaper-time_slice_reaper == father)
+ reaper-time_slice_reaper = NULL;
} while (reaper-exit_state);
list_for_each_safe(_p, _n, father-children) {
p = list_entry(_p, struct task_struct, sibling);
+ if (p-time_slice_reaper == father)
+ p-time_slice_reaper = NULL;
choose_new_parent(p, reaper);
reparent_thread(p, father);
}
Index: linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c
===
--- linux-2.6.21-rc6-mm1.tsfix.orig/kernel/sched.c 2007-04-15
16:56:12.0 +0900
+++ linux-2.6.21-rc6-mm1.tsfix/kernel/sched.c 2007-04-15
16:56:17.0 +0900
@@ -1693,7 +1693,7 @@
* The remainder of the first timeslice might be recovered by
* the parent if the child exits early enough.
*/
- p-first_time_slice = 1;
+ p-time_slice_reaper = current;
p-timestamp = sched_clock();
local_irq_enable();
I am afraid this doesn't work for CLONE_THREAD. Suppose that some sub-thread
(not
main thread) T1 creates another sub-thread, T2.
T2-time_slice_reaper = T1.
then T1 exits, but forget_original_parent(T1) doesn't change
T2-time_slice_reaper,
because T2 is not on T1-children list. Now T2-time_slice_reaper points to an
already freed task_struct.
I intended that CLONE_THREAD case is managed on the do-while loop seeking
`reaper'.
However, anyway, my patch has a bug. On T1 exiting, if there are any living
threads
ahead of T2, T2-time_slice_reaper isn't checked. What a easy mistake ... sorry.
I'll post fixed version soon.
Satoru
-
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
