iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

cgroup, memcg, cpuset: implement cgroup_taskset_for_each_leader()

Browse Source 
It wasn't explicitly documented but, when a process is being migrated,
cpuset and memcg depend on cgroup_taskset_first() returning the
threadgroup leader; however, this approach is somewhat ghetto and
would no longer work for the planned multi-process migration.

This patch introduces explicit cgroup_taskset_for_each_leader() which
iterates over only the threadgroup leaders and replaces
cgroup_taskset_first() usages for accessing the leader with it.

This prepares both memcg and cpuset for multi-process migration.  This
patch also updates the documentation for cgroup_taskset_for_each() to
clarify the iteration rules and removes comments mentioning task
ordering in tasksets.

v2: A previous patch which added threadgroup leader test was dropped.
    Patch updated accordingly.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
This commit is contained in:
Tejun Heo
2015-09-11 15:00:19 -04:00
parent 3df9ca0a2b
commit 4530eddb59
4 changed files with 41 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
mm/memcontrol.c
View File

@@ -4828,7 +4828,7 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css,
{
struct mem_cgroup *memcg = mem_cgroup_from_css(css);
struct mem_cgroup *from;
struct task_struct *p;
struct task_struct *leader, *p;
struct mm_struct *mm;
unsigned long move_flags;
int ret = 0;
@@ -4842,7 +4842,20 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css,
if (!move_flags)
return 0;
p = cgroup_taskset_first(tset);
/*
* Multi-process migrations only happen on the default hierarchy
* where charge immigration is not used. Perform charge
* immigration if @tset contains a leader and whine if there are
* multiple.
*/
p = NULL;
cgroup_taskset_for_each_leader(leader, tset) {
WARN_ON_ONCE(p);
p = leader;
}
if (!p)
return 0;
from = mem_cgroup_from_task(p);
VM_BUG_ON(from == memcg);