[PATCH v4 0/2] cgroups: implement moving a threadgroup's threads atomically with cgroup.procs

[PATCH v4 0/2] cgroups: implement moving a threadgroup's threads atomically with cgroup.procs

[Ben Blum]

This patch series is a revision of http://lkml.org/lkml/2010/6/25/11 .

This patch series implements a write function for the 'cgroup.procs'
per-cgroup file, which enables atomic movement of multithreaded
applications between cgroups. Writing the thread-ID of any thread in a
threadgroup to a cgroup's procs file causes all threads in the group to
be moved to that cgroup safely with respect to threads forking/exiting.
(Possible usage scenario: If running a multithreaded build system that
sucks up system resources, this lets you restrict it all at once into a
new cgroup to keep it under control.)

Example: Suppose pid 31337 clones new threads 31338 and 31339.

# cat /dev/cgroup/tasks
...
31337
31338
31339
# mkdir /dev/cgroup/foo
# echo 31337 > /dev/cgroup/foo/cgroup.procs
# cat /dev/cgroup/foo/tasks
31337
31338
31339

A new lock, called threadgroup_fork_lock and living in signal_struct, is
introduced to ensure atomicity when moving threads between cgroups. It's
taken for writing during the operation, and taking for reading in fork()
around the calls to cgroup_fork() and cgroup_post_fork(). I put calls to
down_read/up_read directly in copy_process(), since new inline functions
seemed like overkill.

-- Ben

---
 Documentation/cgroups/cgroups.txt |   13 -
 include/linux/init_task.h         |    9
 include/linux/sched.h             |   10
 kernel/cgroup.c                   |  426 +++++++++++++++++++++++++++++++++-----
 kernel/cgroup_freezer.c           |    4
 kernel/cpuset.c                   |    4
 kernel/fork.c                     |   16 +
 kernel/ns_cgroup.c                |    4
 kernel/sched.c                    |    4
 9 files changed, 440 insertions(+), 50 deletions(-)

[PATCH v4 0/2] cgroups: implement moving a threadgroup's threads atomically with cgroup.procs

[Ben Blum]

This patch series is a revision of http://lkml.org/lkml/2010/6/25/11 .

This patch series implements a write function for the 'cgroup.procs'
per-cgroup file, which enables atomic movement of multithreaded
applications between cgroups. Writing the thread-ID of any thread in a
threadgroup to a cgroup's procs file causes all threads in the group to
be moved to that cgroup safely with respect to threads forking/exiting.
(Possible usage scenario: If running a multithreaded build system that
sucks up system resources, this lets you restrict it all at once into a
new cgroup to keep it under control.)

Example: Suppose pid 31337 clones new threads 31338 and 31339.

# cat /dev/cgroup/tasks
...
31337
31338
31339
# mkdir /dev/cgroup/foo
# echo 31337 > /dev/cgroup/foo/cgroup.procs
# cat /dev/cgroup/foo/tasks
31337
31338
31339

A new lock, called threadgroup_fork_lock and living in signal_struct, is
introduced to ensure atomicity when moving threads between cgroups. It's
taken for writing during the operation, and taking for reading in fork()
around the calls to cgroup_fork() and cgroup_post_fork(). I put calls to
down_read/up_read directly in copy_process(), since new inline functions
seemed like overkill.

-- Ben

---
 Documentation/cgroups/cgroups.txt |   13 -
 include/linux/init_task.h         |    9
 include/linux/sched.h             |   10
 kernel/cgroup.c                   |  426 +++++++++++++++++++++++++++++++++-----
 kernel/cgroup_freezer.c           |    4
 kernel/cpuset.c                   |    4
 kernel/fork.c                     |   16 +
 kernel/ns_cgroup.c                |    4
 kernel/sched.c                    |    4
 9 files changed, 440 insertions(+), 50 deletions(-)

Re: [PATCH v4 0/2] cgroups: implement moving a threadgroup's threads atomically with cgroup.procs

[Andrew Morton]

On Fri, 30 Jul 2010 19:56:49 -0400
Ben Blum <bblum-OM76b2Iv3yLQjUSlxSEPGw@public.gmane.org> wrote:

> This patch series implements a write function for the 'cgroup.procs'
> per-cgroup file, which enables atomic movement of multithreaded
> applications between cgroups. Writing the thread-ID of any thread in a
> threadgroup to a cgroup's procs file causes all threads in the group to
> be moved to that cgroup safely with respect to threads forking/exiting.
> (Possible usage scenario: If running a multithreaded build system that
> sucks up system resources, this lets you restrict it all at once into a
> new cgroup to keep it under control.)

I can see how that would be useful.  No comments from anyone else?

patch 1/2 makes me cry with all those ifdefs.  Maybe helper functions
would help, but not a lot.

patch 2/2 looks very complicated.

Re: [PATCH v4 0/2] cgroups: implement moving a threadgroup's threads atomically with cgroup.procs

[Andrew Morton]

On Fri, 30 Jul 2010 19:56:49 -0400
Ben Blum <bblum@andrew.cmu.edu> wrote:

> This patch series implements a write function for the 'cgroup.procs'
> per-cgroup file, which enables atomic movement of multithreaded
> applications between cgroups. Writing the thread-ID of any thread in a
> threadgroup to a cgroup's procs file causes all threads in the group to
> be moved to that cgroup safely with respect to threads forking/exiting.
> (Possible usage scenario: If running a multithreaded build system that
> sucks up system resources, this lets you restrict it all at once into a
> new cgroup to keep it under control.)

I can see how that would be useful.  No comments from anyone else?

patch 1/2 makes me cry with all those ifdefs.  Maybe helper functions
would help, but not a lot.

patch 2/2 looks very complicated.

Re: [PATCH v4 0/2] cgroups: implement moving a threadgroup's threads atomically with cgroup.procs

[KAMEZAWA Hiroyuki]

On Tue, 3 Aug 2010 12:58:27 -0700
Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org> wrote:

> On Fri, 30 Jul 2010 19:56:49 -0400
> Ben Blum <bblum-OM76b2Iv3yLQjUSlxSEPGw@public.gmane.org> wrote:
> 
> > This patch series implements a write function for the 'cgroup.procs'
> > per-cgroup file, which enables atomic movement of multithreaded
> > applications between cgroups. Writing the thread-ID of any thread in a
> > threadgroup to a cgroup's procs file causes all threads in the group to
> > be moved to that cgroup safely with respect to threads forking/exiting.
> > (Possible usage scenario: If running a multithreaded build system that
> > sucks up system resources, this lets you restrict it all at once into a
> > new cgroup to keep it under control.)
> 
> I can see how that would be useful.  No comments from anyone else?
> 

I think the feature itself is good and useful. I welcome this.

> patch 1/2 makes me cry with all those ifdefs.  Maybe helper functions
> would help, but not a lot.
> 
Add static inline functions ?


> patch 2/2 looks very complicated.

yes. that's a concern.
I'd like to look deeper, today.

Thanks,
-Kame

Re: [PATCH v4 0/2] cgroups: implement moving a threadgroup's threads atomically with cgroup.procs

[Li Zefan]

Andrew Morton wrote:
> On Fri, 30 Jul 2010 19:56:49 -0400
> Ben Blum <bblum-OM76b2Iv3yLQjUSlxSEPGw@public.gmane.org> wrote:
> 
>> This patch series implements a write function for the 'cgroup.procs'
>> per-cgroup file, which enables atomic movement of multithreaded
>> applications between cgroups. Writing the thread-ID of any thread in a
>> threadgroup to a cgroup's procs file causes all threads in the group to
>> be moved to that cgroup safely with respect to threads forking/exiting.
>> (Possible usage scenario: If running a multithreaded build system that
>> sucks up system resources, this lets you restrict it all at once into a
>> new cgroup to keep it under control.)
> 
> I can see how that would be useful.  No comments from anyone else?
> 

Oleg had been commenting on this patchset, so it would be nice to know
if he's comfortable with the changes in this version.

Re: [PATCH v4 0/2] cgroups: implement moving a threadgroup's threads atomically with cgroup.procs

[Li Zefan]

Andrew Morton wrote:
> On Fri, 30 Jul 2010 19:56:49 -0400
> Ben Blum <bblum@andrew.cmu.edu> wrote:
> 
>> This patch series implements a write function for the 'cgroup.procs'
>> per-cgroup file, which enables atomic movement of multithreaded
>> applications between cgroups. Writing the thread-ID of any thread in a
>> threadgroup to a cgroup's procs file causes all threads in the group to
>> be moved to that cgroup safely with respect to threads forking/exiting.
>> (Possible usage scenario: If running a multithreaded build system that
>> sucks up system resources, this lets you restrict it all at once into a
>> new cgroup to keep it under control.)
> 
> I can see how that would be useful.  No comments from anyone else?
> 

Oleg had been commenting on this patchset, so it would be nice to know
if he's comfortable with the changes in this version.

Re: [PATCH v4 0/2] cgroups: implement moving a threadgroup's threads atomically with cgroup.procs

[KAMEZAWA Hiroyuki]

On Tue, 3 Aug 2010 12:58:27 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Fri, 30 Jul 2010 19:56:49 -0400
> Ben Blum <bblum@andrew.cmu.edu> wrote:
> 
> > This patch series implements a write function for the 'cgroup.procs'
> > per-cgroup file, which enables atomic movement of multithreaded
> > applications between cgroups. Writing the thread-ID of any thread in a
> > threadgroup to a cgroup's procs file causes all threads in the group to
> > be moved to that cgroup safely with respect to threads forking/exiting.
> > (Possible usage scenario: If running a multithreaded build system that
> > sucks up system resources, this lets you restrict it all at once into a
> > new cgroup to keep it under control.)
> 
> I can see how that would be useful.  No comments from anyone else?
> 

I think the feature itself is good and useful. I welcome this.

> patch 1/2 makes me cry with all those ifdefs.  Maybe helper functions
> would help, but not a lot.
> 
Add static inline functions ?


> patch 2/2 looks very complicated.

yes. that's a concern.
I'd like to look deeper, today.

Thanks,
-Kame