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authorTejun Heo <tj@kernel.org>2015-09-16 12:53:17 -0400
committerTejun Heo <tj@kernel.org>2015-09-16 12:53:17 -0400
commit1ed1328792ff46e4bb86a3d7f7be2971f4549f6c (patch)
tree53719cfc0bf81bc7e6fb522944553d9b4fa36cbf /include/linux/init_task.h
parent0c986253b939cc14c69d4adbe2b4121bdf4aa220 (diff)
sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem
Note: This commit was originally committed as d59cfc09c32a but got reverted by 0c986253b939 due to the performance regression from the percpu_rwsem write down/up operations added to cgroup task migration path. percpu_rwsem changes which alleviate the performance issue are pending for v4.4-rc1 merge window. Re-apply. The cgroup side of threadgroup locking uses signal_struct->group_rwsem to synchronize against threadgroup changes. This per-process rwsem adds small overhead to thread creation, exit and exec paths, forces cgroup code paths to do lock-verify-unlock-retry dance in a couple places and makes it impossible to atomically perform operations across multiple processes. This patch replaces signal_struct->group_rwsem with a global percpu_rwsem cgroup_threadgroup_rwsem which is cheaper on the reader side and contained in cgroups proper. This patch converts one-to-one. This does make writer side heavier and lower the granularity; however, cgroup process migration is a fairly cold path, we do want to optimize thread operations over it and cgroup migration operations don't take enough time for the lower granularity to matter. Signed-off-by: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/g/55F8097A.7000206@de.ibm.com Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org>
Diffstat (limited to 'include/linux/init_task.h')
-rw-r--r--include/linux/init_task.h8
1 files changed, 0 insertions, 8 deletions
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index e38681f4912d..d0b380ee7d67 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -25,13 +25,6 @@
extern struct files_struct init_files;
extern struct fs_struct init_fs;
-#ifdef CONFIG_CGROUPS
-#define INIT_GROUP_RWSEM(sig) \
- .group_rwsem = __RWSEM_INITIALIZER(sig.group_rwsem),
-#else
-#define INIT_GROUP_RWSEM(sig)
-#endif
-
#ifdef CONFIG_CPUSETS
#define INIT_CPUSET_SEQ(tsk) \
.mems_allowed_seq = SEQCNT_ZERO(tsk.mems_allowed_seq),
@@ -64,7 +57,6 @@ extern struct fs_struct init_fs;
INIT_PREV_CPUTIME(sig) \
.cred_guard_mutex = \
__MUTEX_INITIALIZER(sig.cred_guard_mutex), \
- INIT_GROUP_RWSEM(sig) \
}
extern struct nsproxy init_nsproxy;