Re: [PATCH] [sched] Don't account time after deadline twice
We calculate difference between two readings of a clock to see how much time has elapsed. Part of the time between rq_clock(rq) - dl_se->deadline can indeed be accounted for by reading a different clock (i.e., rq_clock_task()) if the task was running during the period. And that is how dl_se->runtime is obtained. After all, both clocks are running independently, right? Furthermore, the caller of dl_runtime_exceeded() will still use rq_clock() and dl_se->deadline to determine if we throttle or replenish. Anyway, I have failed to see any steal of time. Could you please give a concrete example (perhaps with numbers)? thanks, -Zhihui On Thu, Jul 3, 2014 at 5:50 AM, Juri Lelli wrote: > On Wed, 2 Jul 2014 19:44:04 -0400 > Zhihui Zhang wrote: > >> My point is that rq_clock(rq) - dl_se->deadline is already part of >> dl_se->runtime, which is decremented before calling dl_runtime_exceeded(). > > But, we decrement dl_se->runtime looking at rq_clock_task(rq), that is > in general <= rq_clock(rq), that we use to handle deadlines. So, if we > do like you suggest, in some cases we could end up stealing some > bandwidth from the system. Indeed, we prefer some pessimism here. > > Thanks, > > - Juri > >> So the following line is not needed in the case of both overrun and missing >> deadline: >> >> dl_se->runtime -= rq_clock(rq) - dl_se->deadline; >> >> Or did I miss anything? >> >> thanks, >> >> >> On Tue, Jul 1, 2014 at 9:59 AM, Juri Lelli wrote: >> >> > On Tue, 1 Jul 2014 15:08:16 +0200 >> > Peter Zijlstra wrote: >> > >> > > On Sun, Jun 29, 2014 at 09:26:10PM -0400, Zhihui Zhang wrote: >> > > > Unless we want to double-penalize an overrun task, the time after the >> > deadline >> > > > and before the current time is already accounted in the negative >> > dl_se->runtime >> > > > value. So we can leave it as is in the case of dmiss && rorun. >> > > >> > > Juri? >> > > >> > > > Signed-off-by: Zhihui Zhang >> > > > --- >> > > > kernel/sched/deadline.c | 6 ++ >> > > > 1 file changed, 2 insertions(+), 4 deletions(-) >> > > > >> > > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c >> > > > index fc4f98b1..67df0d6 100644 >> > > > --- a/kernel/sched/deadline.c >> > > > +++ b/kernel/sched/deadline.c >> > > > @@ -579,10 +579,8 @@ int dl_runtime_exceeded(struct rq *rq, struct >> > sched_dl_entity *dl_se) >> > > > * the next instance. Thus, if we do not account that, we are >> > > > * stealing bandwidth from the system at each deadline miss! >> > > > */ >> > > > - if (dmiss) { >> > > > - dl_se->runtime = rorun ? dl_se->runtime : 0; >> > >> > If we didn't return 0 before, we are going to throttle (or replenish) >> > the entity, and you want runtime to be <=0. So, this is needed. >> > >> > > > - dl_se->runtime -= rq_clock(rq) - dl_se->deadline; >> > > > - } >> > >> > A little pessimism in some cases, due to the fact that we use both >> > rq_clock and rq_clock_task (for the budget). >> > >> > Thanks, >> > >> > - Juri >> > >> > > > + if (dmiss && !rorun) >> > > > + dl_se->runtime = dl_se->deadline - rq_clock(rq); >> > > > >> > > > return 1; >> > > > } >> > > > -- >> > > > 1.8.1.2 >> > > > >> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] [sched] Don't account time after deadline twice
On Wed, 2 Jul 2014 19:44:04 -0400 Zhihui Zhang wrote: > My point is that rq_clock(rq) - dl_se->deadline is already part of > dl_se->runtime, which is decremented before calling dl_runtime_exceeded(). But, we decrement dl_se->runtime looking at rq_clock_task(rq), that is in general <= rq_clock(rq), that we use to handle deadlines. So, if we do like you suggest, in some cases we could end up stealing some bandwidth from the system. Indeed, we prefer some pessimism here. Thanks, - Juri > So the following line is not needed in the case of both overrun and missing > deadline: > > dl_se->runtime -= rq_clock(rq) - dl_se->deadline; > > Or did I miss anything? > > thanks, > > > On Tue, Jul 1, 2014 at 9:59 AM, Juri Lelli wrote: > > > On Tue, 1 Jul 2014 15:08:16 +0200 > > Peter Zijlstra wrote: > > > > > On Sun, Jun 29, 2014 at 09:26:10PM -0400, Zhihui Zhang wrote: > > > > Unless we want to double-penalize an overrun task, the time after the > > deadline > > > > and before the current time is already accounted in the negative > > dl_se->runtime > > > > value. So we can leave it as is in the case of dmiss && rorun. > > > > > > Juri? > > > > > > > Signed-off-by: Zhihui Zhang > > > > --- > > > > kernel/sched/deadline.c | 6 ++ > > > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > > > > index fc4f98b1..67df0d6 100644 > > > > --- a/kernel/sched/deadline.c > > > > +++ b/kernel/sched/deadline.c > > > > @@ -579,10 +579,8 @@ int dl_runtime_exceeded(struct rq *rq, struct > > sched_dl_entity *dl_se) > > > > * the next instance. Thus, if we do not account that, we are > > > > * stealing bandwidth from the system at each deadline miss! > > > > */ > > > > - if (dmiss) { > > > > - dl_se->runtime = rorun ? dl_se->runtime : 0; > > > > If we didn't return 0 before, we are going to throttle (or replenish) > > the entity, and you want runtime to be <=0. So, this is needed. > > > > > > - dl_se->runtime -= rq_clock(rq) - dl_se->deadline; > > > > - } > > > > A little pessimism in some cases, due to the fact that we use both > > rq_clock and rq_clock_task (for the budget). > > > > Thanks, > > > > - Juri > > > > > > + if (dmiss && !rorun) > > > > + dl_se->runtime = dl_se->deadline - rq_clock(rq); > > > > > > > > return 1; > > > > } > > > > -- > > > > 1.8.1.2 > > > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] [sched] Don't account time after deadline twice
On Wed, 2 Jul 2014 19:44:04 -0400 Zhihui Zhang zzhs...@gmail.com wrote: My point is that rq_clock(rq) - dl_se-deadline is already part of dl_se-runtime, which is decremented before calling dl_runtime_exceeded(). But, we decrement dl_se-runtime looking at rq_clock_task(rq), that is in general = rq_clock(rq), that we use to handle deadlines. So, if we do like you suggest, in some cases we could end up stealing some bandwidth from the system. Indeed, we prefer some pessimism here. Thanks, - Juri So the following line is not needed in the case of both overrun and missing deadline: dl_se-runtime -= rq_clock(rq) - dl_se-deadline; Or did I miss anything? thanks, On Tue, Jul 1, 2014 at 9:59 AM, Juri Lelli juri.le...@gmail.com wrote: On Tue, 1 Jul 2014 15:08:16 +0200 Peter Zijlstra pet...@infradead.org wrote: On Sun, Jun 29, 2014 at 09:26:10PM -0400, Zhihui Zhang wrote: Unless we want to double-penalize an overrun task, the time after the deadline and before the current time is already accounted in the negative dl_se-runtime value. So we can leave it as is in the case of dmiss rorun. Juri? Signed-off-by: Zhihui Zhang zzhs...@gmail.com --- kernel/sched/deadline.c | 6 ++ 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index fc4f98b1..67df0d6 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -579,10 +579,8 @@ int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se) * the next instance. Thus, if we do not account that, we are * stealing bandwidth from the system at each deadline miss! */ - if (dmiss) { - dl_se-runtime = rorun ? dl_se-runtime : 0; If we didn't return 0 before, we are going to throttle (or replenish) the entity, and you want runtime to be =0. So, this is needed. - dl_se-runtime -= rq_clock(rq) - dl_se-deadline; - } A little pessimism in some cases, due to the fact that we use both rq_clock and rq_clock_task (for the budget). Thanks, - Juri + if (dmiss !rorun) + dl_se-runtime = dl_se-deadline - rq_clock(rq); return 1; } -- 1.8.1.2 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] [sched] Don't account time after deadline twice
We calculate difference between two readings of a clock to see how much time has elapsed. Part of the time between rq_clock(rq) - dl_se-deadline can indeed be accounted for by reading a different clock (i.e., rq_clock_task()) if the task was running during the period. And that is how dl_se-runtime is obtained. After all, both clocks are running independently, right? Furthermore, the caller of dl_runtime_exceeded() will still use rq_clock() and dl_se-deadline to determine if we throttle or replenish. Anyway, I have failed to see any steal of time. Could you please give a concrete example (perhaps with numbers)? thanks, -Zhihui On Thu, Jul 3, 2014 at 5:50 AM, Juri Lelli juri.le...@gmail.com wrote: On Wed, 2 Jul 2014 19:44:04 -0400 Zhihui Zhang zzhs...@gmail.com wrote: My point is that rq_clock(rq) - dl_se-deadline is already part of dl_se-runtime, which is decremented before calling dl_runtime_exceeded(). But, we decrement dl_se-runtime looking at rq_clock_task(rq), that is in general = rq_clock(rq), that we use to handle deadlines. So, if we do like you suggest, in some cases we could end up stealing some bandwidth from the system. Indeed, we prefer some pessimism here. Thanks, - Juri So the following line is not needed in the case of both overrun and missing deadline: dl_se-runtime -= rq_clock(rq) - dl_se-deadline; Or did I miss anything? thanks, On Tue, Jul 1, 2014 at 9:59 AM, Juri Lelli juri.le...@gmail.com wrote: On Tue, 1 Jul 2014 15:08:16 +0200 Peter Zijlstra pet...@infradead.org wrote: On Sun, Jun 29, 2014 at 09:26:10PM -0400, Zhihui Zhang wrote: Unless we want to double-penalize an overrun task, the time after the deadline and before the current time is already accounted in the negative dl_se-runtime value. So we can leave it as is in the case of dmiss rorun. Juri? Signed-off-by: Zhihui Zhang zzhs...@gmail.com --- kernel/sched/deadline.c | 6 ++ 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index fc4f98b1..67df0d6 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -579,10 +579,8 @@ int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se) * the next instance. Thus, if we do not account that, we are * stealing bandwidth from the system at each deadline miss! */ - if (dmiss) { - dl_se-runtime = rorun ? dl_se-runtime : 0; If we didn't return 0 before, we are going to throttle (or replenish) the entity, and you want runtime to be =0. So, this is needed. - dl_se-runtime -= rq_clock(rq) - dl_se-deadline; - } A little pessimism in some cases, due to the fact that we use both rq_clock and rq_clock_task (for the budget). Thanks, - Juri + if (dmiss !rorun) + dl_se-runtime = dl_se-deadline - rq_clock(rq); return 1; } -- 1.8.1.2 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] [sched] Don't account time after deadline twice
On Tue, 1 Jul 2014 15:08:16 +0200 Peter Zijlstra wrote: > On Sun, Jun 29, 2014 at 09:26:10PM -0400, Zhihui Zhang wrote: > > Unless we want to double-penalize an overrun task, the time after the > > deadline > > and before the current time is already accounted in the negative > > dl_se->runtime > > value. So we can leave it as is in the case of dmiss && rorun. > > Juri? > > > Signed-off-by: Zhihui Zhang > > --- > > kernel/sched/deadline.c | 6 ++ > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > > index fc4f98b1..67df0d6 100644 > > --- a/kernel/sched/deadline.c > > +++ b/kernel/sched/deadline.c > > @@ -579,10 +579,8 @@ int dl_runtime_exceeded(struct rq *rq, struct > > sched_dl_entity *dl_se) > > * the next instance. Thus, if we do not account that, we are > > * stealing bandwidth from the system at each deadline miss! > > */ > > - if (dmiss) { > > - dl_se->runtime = rorun ? dl_se->runtime : 0; If we didn't return 0 before, we are going to throttle (or replenish) the entity, and you want runtime to be <=0. So, this is needed. > > - dl_se->runtime -= rq_clock(rq) - dl_se->deadline; > > - } A little pessimism in some cases, due to the fact that we use both rq_clock and rq_clock_task (for the budget). Thanks, - Juri > > + if (dmiss && !rorun) > > + dl_se->runtime = dl_se->deadline - rq_clock(rq); > > > > return 1; > > } > > -- > > 1.8.1.2 > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] [sched] Don't account time after deadline twice
On Sun, Jun 29, 2014 at 09:26:10PM -0400, Zhihui Zhang wrote: > Unless we want to double-penalize an overrun task, the time after the deadline > and before the current time is already accounted in the negative > dl_se->runtime > value. So we can leave it as is in the case of dmiss && rorun. Juri? > Signed-off-by: Zhihui Zhang > --- > kernel/sched/deadline.c | 6 ++ > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index fc4f98b1..67df0d6 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -579,10 +579,8 @@ int dl_runtime_exceeded(struct rq *rq, struct > sched_dl_entity *dl_se) >* the next instance. Thus, if we do not account that, we are >* stealing bandwidth from the system at each deadline miss! >*/ > - if (dmiss) { > - dl_se->runtime = rorun ? dl_se->runtime : 0; > - dl_se->runtime -= rq_clock(rq) - dl_se->deadline; > - } > + if (dmiss && !rorun) > + dl_se->runtime = dl_se->deadline - rq_clock(rq); > > return 1; > } > -- > 1.8.1.2 > pgp8Lfc6JBkgx.pgp Description: PGP signature
Re: [PATCH] [sched] Don't account time after deadline twice
On Sun, Jun 29, 2014 at 09:26:10PM -0400, Zhihui Zhang wrote: Unless we want to double-penalize an overrun task, the time after the deadline and before the current time is already accounted in the negative dl_se-runtime value. So we can leave it as is in the case of dmiss rorun. Juri? Signed-off-by: Zhihui Zhang zzhs...@gmail.com --- kernel/sched/deadline.c | 6 ++ 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index fc4f98b1..67df0d6 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -579,10 +579,8 @@ int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se) * the next instance. Thus, if we do not account that, we are * stealing bandwidth from the system at each deadline miss! */ - if (dmiss) { - dl_se-runtime = rorun ? dl_se-runtime : 0; - dl_se-runtime -= rq_clock(rq) - dl_se-deadline; - } + if (dmiss !rorun) + dl_se-runtime = dl_se-deadline - rq_clock(rq); return 1; } -- 1.8.1.2 pgp8Lfc6JBkgx.pgp Description: PGP signature
Re: [PATCH] [sched] Don't account time after deadline twice
On Tue, 1 Jul 2014 15:08:16 +0200 Peter Zijlstra pet...@infradead.org wrote: On Sun, Jun 29, 2014 at 09:26:10PM -0400, Zhihui Zhang wrote: Unless we want to double-penalize an overrun task, the time after the deadline and before the current time is already accounted in the negative dl_se-runtime value. So we can leave it as is in the case of dmiss rorun. Juri? Signed-off-by: Zhihui Zhang zzhs...@gmail.com --- kernel/sched/deadline.c | 6 ++ 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index fc4f98b1..67df0d6 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -579,10 +579,8 @@ int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se) * the next instance. Thus, if we do not account that, we are * stealing bandwidth from the system at each deadline miss! */ - if (dmiss) { - dl_se-runtime = rorun ? dl_se-runtime : 0; If we didn't return 0 before, we are going to throttle (or replenish) the entity, and you want runtime to be =0. So, this is needed. - dl_se-runtime -= rq_clock(rq) - dl_se-deadline; - } A little pessimism in some cases, due to the fact that we use both rq_clock and rq_clock_task (for the budget). Thanks, - Juri + if (dmiss !rorun) + dl_se-runtime = dl_se-deadline - rq_clock(rq); return 1; } -- 1.8.1.2 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] [sched] Don't account time after deadline twice
Unless we want to double-penalize an overrun task, the time after the deadline and before the current time is already accounted in the negative dl_se->runtime value. So we can leave it as is in the case of dmiss && rorun. Signed-off-by: Zhihui Zhang --- kernel/sched/deadline.c | 6 ++ 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index fc4f98b1..67df0d6 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -579,10 +579,8 @@ int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se) * the next instance. Thus, if we do not account that, we are * stealing bandwidth from the system at each deadline miss! */ - if (dmiss) { - dl_se->runtime = rorun ? dl_se->runtime : 0; - dl_se->runtime -= rq_clock(rq) - dl_se->deadline; - } + if (dmiss && !rorun) + dl_se->runtime = dl_se->deadline - rq_clock(rq); return 1; } -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] [sched] Don't account time after deadline twice
Unless we want to double-penalize an overrun task, the time after the deadline and before the current time is already accounted in the negative dl_se-runtime value. So we can leave it as is in the case of dmiss rorun. Signed-off-by: Zhihui Zhang zzhs...@gmail.com --- kernel/sched/deadline.c | 6 ++ 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index fc4f98b1..67df0d6 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -579,10 +579,8 @@ int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se) * the next instance. Thus, if we do not account that, we are * stealing bandwidth from the system at each deadline miss! */ - if (dmiss) { - dl_se-runtime = rorun ? dl_se-runtime : 0; - dl_se-runtime -= rq_clock(rq) - dl_se-deadline; - } + if (dmiss !rorun) + dl_se-runtime = dl_se-deadline - rq_clock(rq); return 1; } -- 1.8.1.2 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/