On Wed, 9 Feb 2011 15:10:46 -0800 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 7 Feb 2011 20:35:42 -0500 > Ben Blum <bblum@xxxxxxxxxxxxxx> wrote: > > > On Sun, Dec 26, 2010 at 07:09:19AM -0500, Ben Blum wrote: > > > On Fri, Dec 24, 2010 at 03:22:26AM -0500, Ben Blum wrote: > > > > On Wed, Aug 11, 2010 at 01:46:04AM -0400, Ben Blum wrote: > > > > > On Fri, Jul 30, 2010 at 07:56:49PM -0400, Ben Blum wrote: > > > > > > 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(). > > The above six month old text is the best (and almost the only) > explanation of the rationale for the entire patch series. Is > it still correct and complete? > > > Assuming "yes", then... how do we determine whether the feature is > sufficiently useful to justify merging and maintaining it? Will people > actually use it? > > Was there some particular operational situation which led you to think > that the kernel should have this capability? If so, please help us out here > and lavishly describe it. > In these months, I saw following questions as == Q. I think I put qemu to xxxx cgroup but it never works! A. You need to put all threads in qemu to cgroup. == 'tasks' file is not useful interface for users, I think. (Even if users tend to use put-task-before-exec scheme.) IMHO, from user's side of view, 'tasks' file is a mystery. TID(thread-ID) is one of secrets in Linux + pthread library. For example, on RHEL6, to use gettid(), users has to use syscall() directly. And end-user may not know about thread-ID which is hidden under pthreads. IIRC, there are no interface other than /proc/<pid>/tasks which shows all thread IDs of a process. But it's not atomic. So, I think it's ok to have 'procs' interface for cgroup if overhead/impact of patch is not heavy. Thanks, -Kame _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
