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Date: Mon, 9 Apr 2007 14:29:22 +0400 From: Oleg Nesterov <oleg@...sign.ru> To: Satoru Takeuchi <takeuchi_satoru@...fujitsu.com> Cc: Ingo Molnar <mingo@...e.hu>, Andrew Morton <akpm@...ux-foundation.org>, Mike Galbraith <efault@....de>, linux-kernel@...r.kernel.org Subject: Re: [BUG] scheduler: first timeslice of the exiting thread Satoru Takeuchi wrote: > > a) On sched_fork, the creator share its timeslice with new process. > b) On sched_exit, if the exiting process didn't exhaust its first > timeslice yet, it gives its timeslice to the parent. > > It has no problem on the process model since the creator is the parent. > However, on the thread model, the creator is not the parent, it is same > as the creator's parent. Hence, on this kind of program, the creator > can't retrieve shared timeslice and exausts its timeslice at a rate of > knots. In addition, somehow, the parent (typically shell?) gets extra > timeslice. Yes, this is an old oddity. > I believe it's a bug and the exiting process should give its timeslice > to the creator. Now I have some patch plan to fix this problem as follow: > > a) Add the field for the creator to task_struct. It needs extra memory. ... and locking/complications. The creator may already exited at this time. > b) Doesn't add extra field and have thread's parent the creater, which is > same as process creation. However it has many side effects, for example, > we also need to change sys_getppid() implementation. can't understand this, sorry. Ingo, I think sched_exit() has another buglet, if (unlikely(p->parent->time_slice > task_timeslice(p))) p->parent->time_slice = task_timeslice(p); should be if (unlikely(parent->time_slice > task_timeslice(parent))) parent->time_slice = task_timeslice(parent); The [PATCH 1/2] sched_exit: fix parent->time_slice calculation http://marc.info/?l=linux-kernel&m=115101842505365 was dropped because "[PATCH 2/2]" was very wrong. Could you look at it? Oleg. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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