cpuset: Allow v2 behavior in v1 cgroup

PATCH Superseded Waiman Long 4 participants 8 messages Aug 15, 2017 – Aug 17, 2017

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Waiman Long

author maintainer

2017-08-15 17:27 UTC #0 lore raw

PATCH 1/1 cpuset: Allow v2 behavior in v1 cgroup

Cpuset v2 has some valuable attributes that are not present in v1 because of backward compatibility concern. One of that is the restoration of the original cpu and memory node mask after a hot removal and addition event sequence.

This patch adds a new kernel command line option "cpuset_v2_mode=" to allow cpuset to have v2 behavior in a v1 cgroup when using a non-zero value. This enables users to optionally enable cpuset v2 behavior if they choose to.

Signed-off-by Waiman Long <[email protected]>

---
 Documentation/admin-guide/kernel-parameters.txt |  7 ++++
 kernel/cgroup/cpuset.c                          | 46 ++++++++++++++++++-------
 2 files changed, 40 insertions(+), 13 deletions(-)

Documentation/admin-guide/kernel-parameters.txt +7 -0

index 372cc66..7abca11 100644
@@ -668,6 +668,13 @@
 			on every CPU online, such as boot, and resume from suspend.
 			Default: 10000
 
+	cpuset_v2_mode=	[KNL] Enable cpuset v2 behavior in cpuset v1 cgroups.
+			In v2 mode, the cpus and mems can be restored to
+			their original values after a removal-addition
+			event sequence.
+			0: default value, cpuset v1 keeps legacy behavior.
+			1: cpuset v1 behaves like cpuset v2.
+
 	cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
 			Format:
 			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]

kernel/cgroup/cpuset.c +33 ~~-13~~

118 lines not on this page · raw message

Signature · 1 line

1.8.3.1

Zefan Li

2017-08-16 01:20 UTC #1 lore raw

Quoted 11 lines · Waiman Long

Cpuset v2 has some valuable attributes that are not present in v1 because of backward compatibility concern. One of that is the restoration of the original cpu and memory node mask after a hot removal and addition event sequence.
This patch adds a new kernel command line option "cpuset_v2_mode=" to allow cpuset to have v2 behavior in a v1 cgroup when using a non-zero value. This enables users to optionally enable cpuset v2 behavior if they choose to.
Signed-off-by Waiman Long <[email protected]>

I have no strong objection. I have received quite a few requests for this in the past, and some were from other departments in my company.

Tejun Heo

maintainer

2017-08-16 14:29 UTC #2 lore raw

In reply to Waiman Long

Hello, Waiman.

Documentation/admin-guide/kernel-parameters.txt line 677

Quoted 7 lines · Waiman Long

Documentation/admin-guide/kernel-parameters.txt +7 -0

+	cpuset_v2_mode=	[KNL] Enable cpuset v2 behavior in cpuset v1 cgroups.
+			In v2 mode, the cpus and mems can be restored to
+			their original values after a removal-addition
+			event sequence.
+			0: default value, cpuset v1 keeps legacy behavior.
+			1: cpuset v1 behaves like cpuset v2.
+

It feels weird to make this a kernel boot param when all other options are specified on mount time. Is there a reason why this can't be a mount option too?

Thanks.

Signature · 1 line

tejun

Waiman Long

author maintainer

2017-08-16 14:34 UTC #3 lore raw

Quoted 14 lines · Tejun Heo

Hello, Waiman.
Documentation/admin-guide/kernel-parameters.txt line 677
Quoted 7 lines · Waiman Long
Documentation/admin-guide/kernel-parameters.txt +7 -0
+	cpuset_v2_mode=	[KNL] Enable cpuset v2 behavior in cpuset v1 cgroups.
+			In v2 mode, the cpus and mems can be restored to
+			their original values after a removal-addition
+			event sequence.
+			0: default value, cpuset v1 keeps legacy behavior.
+			1: cpuset v1 behaves like cpuset v2.
+
It feels weird to make this a kernel boot param when all other options are specified on mount time. Is there a reason why this can't be a mount option too?

Quoted 2 lines

Thanks.

Yes, we can certainly make this a mount option instead of a boot time parameter. BTW, where do we usually document the mount options for cgroup?

Cheers,
Longman

Tejun Heo

maintainer

2017-08-16 14:36 UTC #4 lore raw

Hello,

Quoted 6 lines · Waiman Long

Quoted 4 lines
It feels weird to make this a kernel boot param when all other options are specified on mount time. Is there a reason why this can't be a mount option too?
Yes, we can certainly make this a mount option instead of a boot time parameter. BTW, where do we usually document the mount options for cgroup?

I don't think there's a central place. Each controller documents theirs in their own file.

Thanks.

Signature · 1 line

tejun

Waiman Long

author maintainer

2017-08-16 14:39 UTC #5 lore raw

Quoted 7 lines · Tejun Heo

Hello,
Quoted 4 lines · Waiman Long
Quoted 4 lines
It feels weird to make this a kernel boot param when all other options are specified on mount time. Is there a reason why this can't be a mount option too?

Quoted 7 lines

Quoted 2 lines
Yes, we can certainly make this a mount option instead of a boot time parameter. BTW, where do we usually document the mount options for cgroup?
I don't think there's a central place. Each controller documents theirs in their own file.
Thanks.

OK, I am going to update the patch by controlling cpuset behavior by mount option instead.

Thanks,
Longman

kbuild test robot

build bot

2017-08-17 21:06 UTC #6 lore raw

In reply to Waiman Long

url: https://github.com/0day-ci/linux/commits/Waiman-Long/cpuset-Allow-v2-behavior-in-v1-cgroup/20170818-040416 config: i386-randconfig-n0-201733 (attached as .config) compiler: gcc-4.8 (Debian…

Hi Waiman,

[auto build test WARNING on linus/master]
[also build test WARNING on v4.13-rc5 next-20170817]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Waiman-Long/cpuset-Allow-v2-behavior-in-v1-cgroup/20170818-040416
config: i386-randconfig-n0-201733 (attached as .config)
compiler: gcc-4.8 (Debian 4.8.4-1) 4.8.4 reproduce:

        # save the attached .config to linux build tree
        make ARCH=i386

All warnings (new ones prefixed by >>):

kernel/cgroup/cpuset.c: In function 'set_v2_mode':

>> kernel/cgroup/cpuset.c:2145:2: warning: passing argument 3 of 'kstrtol' from incompatible pointer type [enabled by default]
     ret = kstrtol(str, 0, &val);
     ^

In file included from include/linux/list.h:8:0,
from include/linux/kobject.h:20,
from include/linux/device.h:17,
from include/linux/node.h:17,
from include/linux/cpu.h:16,
from kernel/cgroup/cpuset.c:25:
include/linux/kernel.h:332:32: note: expected 'long int *' but argument is of type 'ssize_t *'
static inline int __must_check kstrtol(const char *s, unsigned int base, long *res)
^

vim +/kstrtol +2145 kernel/cgroup/cpuset.c

2138
2139 static int __init set_v2_mode(char *str)
2140 {
2141 ssize_t ret, val;
2142
2143 if (!str)
2144 return 0;

> 2145		ret = kstrtol(str, 0, &val);

2146 cpuset_v2_mode = !!val;
2147 return ret;
2148 }
2149 __setup("cpuset_v2_mode=", set_v2_mode);
2150

---
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kbuild test robot

build bot

2017-08-17 21:14 UTC #7 lore raw

In reply to Waiman Long

url: https://github.com/0day-ci/linux/commits/Waiman-Long/cpuset-Allow-v2-behavior-in-v1-cgroup/20170818-040416 config: i386-defconfig (attached as .config) compiler: gcc-6 (Debian 6.2.0-3) 6.2.0…

Hi Waiman,

[auto build test ERROR on linus/master]
[also build test ERROR on v4.13-rc5 next-20170817]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Waiman-Long/cpuset-Allow-v2-behavior-in-v1-cgroup/20170818-040416
config: i386-defconfig (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901 reproduce:

        # save the attached .config to linux build tree
        make ARCH=i386

All errors (new ones prefixed by >>):

kernel/cgroup/cpuset.c: In function 'set_v2_mode':

>> kernel/cgroup/cpuset.c:2145:24: error: passing argument 3 of 'kstrtol' from incompatible pointer type [-Werror=incompatible-pointer-types]
     ret = kstrtol(str, 0, &val);
                           ^

In file included from include/linux/list.h:8:0,
from include/linux/kobject.h:20,
from include/linux/device.h:17,
from include/linux/node.h:17,
from include/linux/cpu.h:16,
from kernel/cgroup/cpuset.c:25:
include/linux/kernel.h:332:32: note: expected 'long int *' but argument is of type 'ssize_t * {aka int *}'
static inline int __must_check kstrtol(const char *s, unsigned int base, long *res)
^~~~~~~
cc1: some warnings being treated as errors

vim +/kstrtol +2145 kernel/cgroup/cpuset.c

2138
2139 static int __init set_v2_mode(char *str)
2140 {
2141 ssize_t ret, val;
2142
2143 if (!str)
2144 return 0;

> 2145		ret = kstrtol(str, 0, &val);

2146 cpuset_v2_mode = !!val;
2147 return ret;
2148 }
2149 __setup("cpuset_v2_mode=", set_v2_mode);
2150

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