[LTP] [PATCH 0/2] Two fixes for sysctl_sched_rr

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* [LTP] [PATCH 0/2] Two fixes for sysctl_sched_rr_timeslice
@ 2023-07-19 10:37 ` Cyril Hrubis
  0 siblings, 0 replies; 16+ messages in thread
From: Cyril Hrubis @ 2023-07-19 10:37 UTC (permalink / raw)
  To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
	Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
	Daniel Bristot de Oliveira, Valentin Schneider, linux-kernel
  Cc: ltp

- Fixes rounding error for initial value with CONFIG_HZ_300

- Fixes read from the file after reset to default (by writing val <= 0)

Cyril Hrubis (2):
  sched/rt: Fix sysctl_sched_rr_timeslice intial value
  sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset

 kernel/sched/rt.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

-- 
2.41.0


-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH 0/2] Two fixes for sysctl_sched_rr_timeslice
@ 2023-07-19 10:37 ` Cyril Hrubis
  0 siblings, 0 replies; 16+ messages in thread
From: Cyril Hrubis @ 2023-07-19 10:37 UTC (permalink / raw)
  To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
	Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
	Daniel Bristot de Oliveira, Valentin Schneider, linux-kernel
  Cc: ltp, Cyril Hrubis

- Fixes rounding error for initial value with CONFIG_HZ_300

- Fixes read from the file after reset to default (by writing val <= 0)

Cyril Hrubis (2):
  sched/rt: Fix sysctl_sched_rr_timeslice intial value
  sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset

 kernel/sched/rt.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

-- 
2.41.0


^ permalink raw reply	[flat|nested] 16+ messages in thread

* [LTP] [PATCH 1/2] sched/rt: Fix sysctl_sched_rr_timeslice intial value
  2023-07-19 10:37 ` Cyril Hrubis
@ 2023-07-19 10:37   ` Cyril Hrubis
  -1 siblings, 0 replies; 16+ messages in thread
From: Cyril Hrubis @ 2023-07-19 10:37 UTC (permalink / raw)
  To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
	Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
	Daniel Bristot de Oliveira, Valentin Schneider, linux-kernel
  Cc: Jiri Bohac, ltp

Thre is 10% rounding error in the intial value of the
sysctl_sched_rr_timeslice with  CONFIG_HZ_300=y.

This was found with LTP test sched_rr_get_interval01:

sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90
sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90

What this test does is to compare the return value from the
sched_rr_get_interval() and the sched_rr_timeslice_ms sysctl file and
fails if they do not match.

The prolem it found is the intial sysctl file value which was computed as:

static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;

which works fine as long as MSEC_PER_SEC is multiple of HZ, however it
introduces 10% rounding error for CONFIG_HZ_300:

(MSEC_PER_SEC / HZ) * (100 * HZ / 1000)

(1000 / 300) * (100 * 300 / 1000)

3 * 30 = 90

This can be easily fixed by reversing the order of the multiplication
and division. After this fix we get:

(MSEC_PER_SEC * (100 * HZ / 1000)) / HZ

(1000 * (100 * 300 / 1000)) / 300

(1000 * 30) / 300 = 100

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
CC: Jiri Bohac <jbohac@suse.cz>
---
 kernel/sched/rt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 00e0e5074115..185d3d749f6b 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -25,7 +25,7 @@ unsigned int sysctl_sched_rt_period = 1000000;
 int sysctl_sched_rt_runtime = 950000;
 
 #ifdef CONFIG_SYSCTL
-static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
+static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;
 static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
 		size_t *lenp, loff_t *ppos);
 static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,
-- 
2.41.0


-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

^ permalink raw reply related	[flat|nested] 16+ messages in thread

* [PATCH 1/2] sched/rt: Fix sysctl_sched_rr_timeslice intial value
@ 2023-07-19 10:37   ` Cyril Hrubis
  0 siblings, 0 replies; 16+ messages in thread
From: Cyril Hrubis @ 2023-07-19 10:37 UTC (permalink / raw)
  To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
	Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
	Daniel Bristot de Oliveira, Valentin Schneider, linux-kernel
  Cc: ltp, Cyril Hrubis, Jiri Bohac

Thre is 10% rounding error in the intial value of the
sysctl_sched_rr_timeslice with  CONFIG_HZ_300=y.

This was found with LTP test sched_rr_get_interval01:

sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90
sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90

What this test does is to compare the return value from the
sched_rr_get_interval() and the sched_rr_timeslice_ms sysctl file and
fails if they do not match.

The prolem it found is the intial sysctl file value which was computed as:

static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;

which works fine as long as MSEC_PER_SEC is multiple of HZ, however it
introduces 10% rounding error for CONFIG_HZ_300:

(MSEC_PER_SEC / HZ) * (100 * HZ / 1000)

(1000 / 300) * (100 * 300 / 1000)

3 * 30 = 90

This can be easily fixed by reversing the order of the multiplication
and division. After this fix we get:

(MSEC_PER_SEC * (100 * HZ / 1000)) / HZ

(1000 * (100 * 300 / 1000)) / 300

(1000 * 30) / 300 = 100

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
CC: Jiri Bohac <jbohac@suse.cz>
---
 kernel/sched/rt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 00e0e5074115..185d3d749f6b 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -25,7 +25,7 @@ unsigned int sysctl_sched_rt_period = 1000000;
 int sysctl_sched_rt_runtime = 950000;
 
 #ifdef CONFIG_SYSCTL
-static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
+static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;
 static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
 		size_t *lenp, loff_t *ppos);
 static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 16+ messages in thread

* Re: [LTP] [PATCH 1/2] sched/rt: Fix sysctl_sched_rr_timeslice intial value
  2023-07-19 10:37   ` Cyril Hrubis
@ 2023-07-19 11:21     ` Petr Vorel
  -1 siblings, 0 replies; 16+ messages in thread
From: Petr Vorel @ 2023-07-19 11:21 UTC (permalink / raw)
  To: Cyril Hrubis
  Cc: Juri Lelli, Shile Zhang, Valentin Schneider, Vincent Guittot,
	Jiri Bohac, Peter Zijlstra, Shile Zhang, linux-kernel,
	Steven Rostedt, Ben Segall, Ingo Molnar, Mel Gorman,
	Daniel Bristot de Oliveira, Dietmar Eggemann, ltp

Hi,

[ Cc Shile Zhang ]

> Thre is 10% rounding error in the intial value of the
> sysctl_sched_rr_timeslice with  CONFIG_HZ_300=y.

> This was found with LTP test sched_rr_get_interval01:

> sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
> sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
> sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90
> sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
> sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
> sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90

> What this test does is to compare the return value from the
> sched_rr_get_interval() and the sched_rr_timeslice_ms sysctl file and
> fails if they do not match.

> The prolem it found is the intial sysctl file value which was computed as:

> static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;

> which works fine as long as MSEC_PER_SEC is multiple of HZ, however it
> introduces 10% rounding error for CONFIG_HZ_300:

> (MSEC_PER_SEC / HZ) * (100 * HZ / 1000)

> (1000 / 300) * (100 * 300 / 1000)

> 3 * 30 = 90

> This can be easily fixed by reversing the order of the multiplication
> and division. After this fix we get:

> (MSEC_PER_SEC * (100 * HZ / 1000)) / HZ

> (1000 * (100 * 300 / 1000)) / 300

> (1000 * 30) / 300 = 100

> Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
> CC: Jiri Bohac <jbohac@suse.cz>
> ---
>  kernel/sched/rt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 00e0e5074115..185d3d749f6b 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -25,7 +25,7 @@ unsigned int sysctl_sched_rt_period = 1000000;
>  int sysctl_sched_rt_runtime = 950000;

>  #ifdef CONFIG_SYSCTL
> -static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
> +static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;

It looks like very old bug, from v4.11-rc1. I guess this should go to all stable
and LTS kernels.

Fixes: 975e155ed873 ("sched/rt: Show the 'sched_rr_timeslice' SCHED_RR timeslice tuning knob in milliseconds")

Reviewed-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

>  static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
>  		size_t *lenp, loff_t *ppos);
>  static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [LTP] [PATCH 1/2] sched/rt: Fix sysctl_sched_rr_timeslice intial value
@ 2023-07-19 11:21     ` Petr Vorel
  0 siblings, 0 replies; 16+ messages in thread
From: Petr Vorel @ 2023-07-19 11:21 UTC (permalink / raw)
  To: Cyril Hrubis
  Cc: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
	Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
	Daniel Bristot de Oliveira, Valentin Schneider, linux-kernel,
	Jiri Bohac, ltp, Shile Zhang, Shile Zhang

Hi,

[ Cc Shile Zhang ]

> Thre is 10% rounding error in the intial value of the
> sysctl_sched_rr_timeslice with  CONFIG_HZ_300=y.

> This was found with LTP test sched_rr_get_interval01:

> sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
> sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
> sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90
> sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
> sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
> sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90

> What this test does is to compare the return value from the
> sched_rr_get_interval() and the sched_rr_timeslice_ms sysctl file and
> fails if they do not match.

> The prolem it found is the intial sysctl file value which was computed as:

> static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;

> which works fine as long as MSEC_PER_SEC is multiple of HZ, however it
> introduces 10% rounding error for CONFIG_HZ_300:

> (MSEC_PER_SEC / HZ) * (100 * HZ / 1000)

> (1000 / 300) * (100 * 300 / 1000)

> 3 * 30 = 90

> This can be easily fixed by reversing the order of the multiplication
> and division. After this fix we get:

> (MSEC_PER_SEC * (100 * HZ / 1000)) / HZ

> (1000 * (100 * 300 / 1000)) / 300

> (1000 * 30) / 300 = 100

> Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
> CC: Jiri Bohac <jbohac@suse.cz>
> ---
>  kernel/sched/rt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 00e0e5074115..185d3d749f6b 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -25,7 +25,7 @@ unsigned int sysctl_sched_rt_period = 1000000;
>  int sysctl_sched_rt_runtime = 950000;

>  #ifdef CONFIG_SYSCTL
> -static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
> +static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;

It looks like very old bug, from v4.11-rc1. I guess this should go to all stable
and LTS kernels.

Fixes: 975e155ed873 ("sched/rt: Show the 'sched_rr_timeslice' SCHED_RR timeslice tuning knob in milliseconds")

Reviewed-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

>  static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
>  		size_t *lenp, loff_t *ppos);
>  static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [LTP] [PATCH 1/2] sched/rt: Fix sysctl_sched_rr_timeslice intial value
  2023-07-19 10:37   ` Cyril Hrubis
@ 2023-07-20  9:57     ` Mel Gorman
  -1 siblings, 0 replies; 16+ messages in thread
From: Mel Gorman @ 2023-07-20  9:57 UTC (permalink / raw)
  To: Cyril Hrubis
  Cc: Juri Lelli, Valentin Schneider, Vincent Guittot, Jiri Bohac,
	Peter Zijlstra, linux-kernel, Steven Rostedt, Ben Segall,
	Ingo Molnar, Daniel Bristot de Oliveira, Dietmar Eggemann, ltp

On Wed, Jul 19, 2023 at 12:37:42PM +0200, Cyril Hrubis wrote:
> Thre is 10% rounding error in the intial value of the
> sysctl_sched_rr_timeslice with  CONFIG_HZ_300=y.
> 
> This was found with LTP test sched_rr_get_interval01:
> 
> sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
> sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
> sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90
> sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
> sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
> sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90
> 
> What this test does is to compare the return value from the
> sched_rr_get_interval() and the sched_rr_timeslice_ms sysctl file and
> fails if they do not match.
> 
> The prolem it found is the intial sysctl file value which was computed as:
> 
> static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
> 
> which works fine as long as MSEC_PER_SEC is multiple of HZ, however it
> introduces 10% rounding error for CONFIG_HZ_300:
> 
> (MSEC_PER_SEC / HZ) * (100 * HZ / 1000)
> 
> (1000 / 300) * (100 * 300 / 1000)
> 
> 3 * 30 = 90
> 
> This can be easily fixed by reversing the order of the multiplication
> and division. After this fix we get:
> 
> (MSEC_PER_SEC * (100 * HZ / 1000)) / HZ
> 
> (1000 * (100 * 300 / 1000)) / 300
> 
> (1000 * 30) / 300 = 100
> 
> Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
> CC: Jiri Bohac <jbohac@suse.cz>

Acked-by: Mel Gorman <mgorman@suse.de>

-- 
Mel Gorman
SUSE Labs

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH 1/2] sched/rt: Fix sysctl_sched_rr_timeslice intial value
@ 2023-07-20  9:57     ` Mel Gorman
  0 siblings, 0 replies; 16+ messages in thread
From: Mel Gorman @ 2023-07-20  9:57 UTC (permalink / raw)
  To: Cyril Hrubis
  Cc: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
	Dietmar Eggemann, Steven Rostedt, Ben Segall,
	Daniel Bristot de Oliveira, Valentin Schneider, linux-kernel, ltp,
	Jiri Bohac

On Wed, Jul 19, 2023 at 12:37:42PM +0200, Cyril Hrubis wrote:
> Thre is 10% rounding error in the intial value of the
> sysctl_sched_rr_timeslice with  CONFIG_HZ_300=y.
> 
> This was found with LTP test sched_rr_get_interval01:
> 
> sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
> sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
> sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90
> sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
> sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
> sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90
> 
> What this test does is to compare the return value from the
> sched_rr_get_interval() and the sched_rr_timeslice_ms sysctl file and
> fails if they do not match.
> 
> The prolem it found is the intial sysctl file value which was computed as:
> 
> static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
> 
> which works fine as long as MSEC_PER_SEC is multiple of HZ, however it
> introduces 10% rounding error for CONFIG_HZ_300:
> 
> (MSEC_PER_SEC / HZ) * (100 * HZ / 1000)
> 
> (1000 / 300) * (100 * 300 / 1000)
> 
> 3 * 30 = 90
> 
> This can be easily fixed by reversing the order of the multiplication
> and division. After this fix we get:
> 
> (MSEC_PER_SEC * (100 * HZ / 1000)) / HZ
> 
> (1000 * (100 * 300 / 1000)) / 300
> 
> (1000 * 30) / 300 = 100
> 
> Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
> CC: Jiri Bohac <jbohac@suse.cz>

Acked-by: Mel Gorman <mgorman@suse.de>

-- 
Mel Gorman
SUSE Labs

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [LTP] [PATCH 1/2] sched/rt: Fix sysctl_sched_rr_timeslice intial value
  2023-07-19 10:37   ` Cyril Hrubis
@ 2023-07-21 16:16     ` Petr Vorel
  -1 siblings, 0 replies; 16+ messages in thread
From: Petr Vorel @ 2023-07-21 16:16 UTC (permalink / raw)
  To: chrubis
  Cc: juri.lelli, jbohac, vincent.guittot, peterz, linux-kernel,
	rostedt, bsegall, mingo, mgorman, vschneid, bristot,
	dietmar.eggemann, ltp

Tested-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [LTP] [PATCH 1/2] sched/rt: Fix sysctl_sched_rr_timeslice intial value
@ 2023-07-21 16:16     ` Petr Vorel
  0 siblings, 0 replies; 16+ messages in thread
From: Petr Vorel @ 2023-07-21 16:16 UTC (permalink / raw)
  To: chrubis
  Cc: bristot, bsegall, dietmar.eggemann, jbohac, juri.lelli,
	linux-kernel, ltp, mgorman, mingo, peterz, rostedt,
	vincent.guittot, vschneid, Petr Vorel

Tested-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [LTP] [PATCH 2/2] sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset
  2023-07-19 10:37 ` Cyril Hrubis
@ 2023-07-19 10:37   ` Cyril Hrubis
  -1 siblings, 0 replies; 16+ messages in thread
From: Cyril Hrubis @ 2023-07-19 10:37 UTC (permalink / raw)
  To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
	Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
	Daniel Bristot de Oliveira, Valentin Schneider, linux-kernel
  Cc: Jiri Bohac, ltp

The sched_rr_timeslice can be reset to default by writing value that is
<= 0. However after reading from this file we always got the last value
written, which is not useful at all.

$ echo -1 > /proc/sys/kernel/sched_rr_timeslice_ms
$ cat /proc/sys/kernel/sched_rr_timeslice_ms
-1

Fix this by setting the variable that holds the sysctl file value to the
jiffies_to_msecs(RR_TIMESLICE) in case that <= 0 value was written.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
CC: Jiri Bohac <jbohac@suse.cz>
---
 kernel/sched/rt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 185d3d749f6b..0597ba0f85ff 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -3062,6 +3062,9 @@ static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,
 		sched_rr_timeslice =
 			sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
 			msecs_to_jiffies(sysctl_sched_rr_timeslice);
+
+		if (sysctl_sched_rr_timeslice <= 0)
+			sysctl_sched_rr_timeslice = jiffies_to_msecs(RR_TIMESLICE);
 	}
 	mutex_unlock(&mutex);
 
-- 
2.41.0


-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

^ permalink raw reply related	[flat|nested] 16+ messages in thread

* [PATCH 2/2] sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset
@ 2023-07-19 10:37   ` Cyril Hrubis
  0 siblings, 0 replies; 16+ messages in thread
From: Cyril Hrubis @ 2023-07-19 10:37 UTC (permalink / raw)
  To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
	Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
	Daniel Bristot de Oliveira, Valentin Schneider, linux-kernel
  Cc: ltp, Cyril Hrubis, Jiri Bohac

The sched_rr_timeslice can be reset to default by writing value that is
<= 0. However after reading from this file we always got the last value
written, which is not useful at all.

$ echo -1 > /proc/sys/kernel/sched_rr_timeslice_ms
$ cat /proc/sys/kernel/sched_rr_timeslice_ms
-1

Fix this by setting the variable that holds the sysctl file value to the
jiffies_to_msecs(RR_TIMESLICE) in case that <= 0 value was written.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
CC: Jiri Bohac <jbohac@suse.cz>
---
 kernel/sched/rt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 185d3d749f6b..0597ba0f85ff 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -3062,6 +3062,9 @@ static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,
 		sched_rr_timeslice =
 			sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
 			msecs_to_jiffies(sysctl_sched_rr_timeslice);
+
+		if (sysctl_sched_rr_timeslice <= 0)
+			sysctl_sched_rr_timeslice = jiffies_to_msecs(RR_TIMESLICE);
 	}
 	mutex_unlock(&mutex);
 
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 16+ messages in thread

* Re: [LTP] [PATCH 2/2] sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset
  2023-07-19 10:37   ` Cyril Hrubis
@ 2023-07-20 10:00     ` Mel Gorman
  -1 siblings, 0 replies; 16+ messages in thread
From: Mel Gorman @ 2023-07-20 10:00 UTC (permalink / raw)
  To: Cyril Hrubis
  Cc: Juri Lelli, Valentin Schneider, Vincent Guittot, Jiri Bohac,
	Peter Zijlstra, linux-kernel, Steven Rostedt, Ben Segall,
	Ingo Molnar, Daniel Bristot de Oliveira, Dietmar Eggemann, ltp

On Wed, Jul 19, 2023 at 12:37:43PM +0200, Cyril Hrubis wrote:
> The sched_rr_timeslice can be reset to default by writing value that is
> <= 0. However after reading from this file we always got the last value
> written, which is not useful at all.
> 
> $ echo -1 > /proc/sys/kernel/sched_rr_timeslice_ms
> $ cat /proc/sys/kernel/sched_rr_timeslice_ms
> -1
> 
> Fix this by setting the variable that holds the sysctl file value to the
> jiffies_to_msecs(RR_TIMESLICE) in case that <= 0 value was written.
> 
> Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
> CC: Jiri Bohac <jbohac@suse.cz>

Acked-by: Mel Gorman <mgorman@suse.de>

-- 
Mel Gorman
SUSE Labs

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH 2/2] sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset
@ 2023-07-20 10:00     ` Mel Gorman
  0 siblings, 0 replies; 16+ messages in thread
From: Mel Gorman @ 2023-07-20 10:00 UTC (permalink / raw)
  To: Cyril Hrubis
  Cc: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
	Dietmar Eggemann, Steven Rostedt, Ben Segall,
	Daniel Bristot de Oliveira, Valentin Schneider, linux-kernel, ltp,
	Jiri Bohac

On Wed, Jul 19, 2023 at 12:37:43PM +0200, Cyril Hrubis wrote:
> The sched_rr_timeslice can be reset to default by writing value that is
> <= 0. However after reading from this file we always got the last value
> written, which is not useful at all.
> 
> $ echo -1 > /proc/sys/kernel/sched_rr_timeslice_ms
> $ cat /proc/sys/kernel/sched_rr_timeslice_ms
> -1
> 
> Fix this by setting the variable that holds the sysctl file value to the
> jiffies_to_msecs(RR_TIMESLICE) in case that <= 0 value was written.
> 
> Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
> CC: Jiri Bohac <jbohac@suse.cz>

Acked-by: Mel Gorman <mgorman@suse.de>

-- 
Mel Gorman
SUSE Labs

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [LTP] [PATCH 2/2] sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset
  2023-07-19 10:37   ` Cyril Hrubis
@ 2023-07-21 16:14     ` Petr Vorel
  -1 siblings, 0 replies; 16+ messages in thread
From: Petr Vorel @ 2023-07-21 16:14 UTC (permalink / raw)
  To: chrubis
  Cc: juri.lelli, jbohac, vincent.guittot, peterz, linux-kernel,
	rostedt, bsegall, mingo, mgorman, vschneid, bristot,
	dietmar.eggemann, ltp

Reviewed-by: Petr Vorel <pvorel@suse.cz>
Tested-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH 2/2] sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset
@ 2023-07-21 16:14     ` Petr Vorel
  0 siblings, 0 replies; 16+ messages in thread
From: Petr Vorel @ 2023-07-21 16:14 UTC (permalink / raw)
  To: chrubis
  Cc: bristot, bsegall, dietmar.eggemann, jbohac, juri.lelli,
	linux-kernel, ltp, mgorman, mingo, peterz, rostedt,
	vincent.guittot, vschneid, Petr Vorel

Reviewed-by: Petr Vorel <pvorel@suse.cz>
Tested-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

^ permalink raw reply	[flat|nested] 16+ messages in thread

end of thread, other threads:[~2023-07-21 16:18 UTC | newest]

Thread overview: 16+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-07-19 10:37 [LTP] [PATCH 0/2] Two fixes for sysctl_sched_rr_timeslice Cyril Hrubis
2023-07-19 10:37 ` Cyril Hrubis
2023-07-19 10:37 ` [LTP] [PATCH 1/2] sched/rt: Fix sysctl_sched_rr_timeslice intial value Cyril Hrubis
2023-07-19 10:37   ` Cyril Hrubis
2023-07-19 11:21   ` [LTP] " Petr Vorel
2023-07-19 11:21     ` Petr Vorel
2023-07-20  9:57   ` Mel Gorman
2023-07-20  9:57     ` Mel Gorman
2023-07-21 16:16   ` [LTP] " Petr Vorel
2023-07-21 16:16     ` Petr Vorel
2023-07-19 10:37 ` [LTP] [PATCH 2/2] sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset Cyril Hrubis
2023-07-19 10:37   ` Cyril Hrubis
2023-07-20 10:00   ` [LTP] " Mel Gorman
2023-07-20 10:00     ` Mel Gorman
2023-07-21 16:14   ` [LTP] " Petr Vorel
2023-07-21 16:14     ` Petr Vorel

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