On 2/26/08, J.C. Pizarro <[EMAIL PROTECTED]> wrote: > On 2008/2/25, Andrew Morton <[EMAIL PROTECTED]> wrote: > > On Sun, 24 Feb 2008 14:12:47 +0100 "J.C. Pizarro" <[EMAIL PROTECTED]> > wrote: > > > > > It's statistic, yes, but it's a very important parameter for the > CPU-scheduler. > > > The CPU-scheduler will know the number of context switches of each task > > > before of to take a blind decision into infinitum!. > > > > > > We already have these: > > > > unsigned long nvcsw, nivcsw; /* context switch counts */ > > > > in the task_struct. > > 1. They use "unsigned long" instead "unsigned long long". > 2. They use "= 0;" instead of "= 0ULL";
Very funny. > 3. They don't use ++ (incr. by one per ctxt-switch). No they do, read schedule() already. > 4. I don't like the separation of voluntary and involuntary ctxt-switches, > and i don't understand the utility of this separation. Ah, that's why you don't like it. > The tsk->nvcsw & tsk->nivcsw mean different to i had proposed. > > It's simple, when calling to function kernel/sched.c:context_switch(..) > to do ++, but they don't do it. > > I propose you > 1. unsigned long long tsk->ncsw = 0ULL; and tsk->ncsw++; > 2. unsigned long long tsk->last_registered_ncsw = tsk->ncsw; when it's > polling. > 3. long tsk->vcsw = ( tsk->ncsw - tsk->last_registered_ncsw ) / ( t2 - t1 ) > /* velocity of task (ctxt-switches per second), (t1 != t2 in seconds > for no zerodiv) > 4. long tsk->last_registered_vcsw = tsk->vcsw; > 5. long tsk->normalized_vcsw = > (1 - alpha)*tsk->last_registered_vcsw + alpha*tsk->vcsw; /* 0<alpha<1 > */ 6. Profit. As I understood the idea of CFS, all interactivity heuristics were bitbucketed, so you'll add them back (you won't, of course, because you can't be arsed to send a patch) So best course of action it to describe workload and setup (distro, relevant .config items and so on.) on which CFS behaves poorly. -- 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/
