Because SCHED_FIFO is a broken scheduler model (see previous patches)
take away the priority field, the kernel can't possibly make an
informed decision.
In this case, use fifo_low, because it only cares about being above
SCHED_NORMAL. Effectively no change in behaviour.
XXX: this driver is still complete crap; why isn't it using proper
idle injection or at the very least play_idle() ?
Cc: [email protected]
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Ingo Molnar <[email protected]>
---
drivers/acpi/acpi_pad.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -136,12 +136,11 @@ static unsigned int idle_pct = 5; /* per
static unsigned int round_robin_time = 1; /* second */
static int power_saving_thread(void *data)
{
- struct sched_param param = {.sched_priority = 1};
int do_sleep;
unsigned int tsk_index = (unsigned long)data;
u64 last_jiffies = 0;
- sched_setscheduler(current, SCHED_RR, ¶m);
+ sched_set_fifo_low(current);
while (!kthread_should_stop()) {
unsigned long expire_time;
On 22/04/2020 13:27, Peter Zijlstra wrote:
> Because SCHED_FIFO is a broken scheduler model (see previous patches)
> take away the priority field, the kernel can't possibly make an
> informed decision.
>
> In this case, use fifo_low, because it only cares about being above
> SCHED_NORMAL. Effectively no change in behaviour.
>
> XXX: this driver is still complete crap; why isn't it using proper
> idle injection or at the very least play_idle() ?
>
> Cc: [email protected]
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
> Reviewed-by: Ingo Molnar <[email protected]>
> ---
> drivers/acpi/acpi_pad.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> --- a/drivers/acpi/acpi_pad.c
> +++ b/drivers/acpi/acpi_pad.c
> @@ -136,12 +136,11 @@ static unsigned int idle_pct = 5; /* per
> static unsigned int round_robin_time = 1; /* second */
> static int power_saving_thread(void *data)
> {
> - struct sched_param param = {.sched_priority = 1};
> int do_sleep;
> unsigned int tsk_index = (unsigned long)data;
> u64 last_jiffies = 0;
>
> - sched_setscheduler(current, SCHED_RR, ¶m);
I was wondering what happened to the SCHED_RR cases but as I can see now
they are handled here and in the next patch.
> + sched_set_fifo_low(current);
>
> while (!kthread_should_stop()) {
> unsigned long expire_time;
>
>
On Wed, Apr 22, 2020 at 06:45:36PM +0200, Dietmar Eggemann wrote:
> On 22/04/2020 13:27, Peter Zijlstra wrote:
> > Because SCHED_FIFO is a broken scheduler model (see previous patches)
> > take away the priority field, the kernel can't possibly make an
> > informed decision.
> >
> > In this case, use fifo_low, because it only cares about being above
> > SCHED_NORMAL. Effectively no change in behaviour.
> >
> > XXX: this driver is still complete crap; why isn't it using proper
> > idle injection or at the very least play_idle() ?
> >
> > Cc: [email protected]
> > Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
> > Reviewed-by: Ingo Molnar <[email protected]>
> > ---
> > drivers/acpi/acpi_pad.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > --- a/drivers/acpi/acpi_pad.c
> > +++ b/drivers/acpi/acpi_pad.c
> > @@ -136,12 +136,11 @@ static unsigned int idle_pct = 5; /* per
> > static unsigned int round_robin_time = 1; /* second */
> > static int power_saving_thread(void *data)
> > {
> > - struct sched_param param = {.sched_priority = 1};
> > int do_sleep;
> > unsigned int tsk_index = (unsigned long)data;
> > u64 last_jiffies = 0;
> >
> > - sched_setscheduler(current, SCHED_RR, ¶m);
>
> I was wondering what happened to the SCHED_RR cases but as I can see now
> they are handled here and in the next patch.
Oh right; I completely forgot to mention that in the Changelog didn't I
:-(
In this case, this driver is a broken piece of crap and doing fake idle
with RR is just plain idiotic. Also note the WARNs in play_idle().
Also, rjw, what was the point of renmaing play_idle() to
play_idle_precise() if there is only one anyway? The changelog talks
about adding play_idle_precise() but the patch (rightfully) doesn't add
another version but replaces the existing one. But why change the name?!