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author | Tejun Heo <tj@kernel.org> | 2013-06-16 16:12:26 -0700 |
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committer | Tejun Heo <tj@kernel.org> | 2013-06-16 16:12:26 -0700 |
commit | a4244454df1296e90cc961c1b636b1176ef0d9a0 (patch) | |
tree | 9be151f1e7a791dbf2d146fc5283ed246562d7f1 /COPYING | |
parent | dbece3a0f1ef0b19aff1cc6ed0942fec9ab98de1 (diff) | |
download | op-kernel-dev-a4244454df1296e90cc961c1b636b1176ef0d9a0.zip op-kernel-dev-a4244454df1296e90cc961c1b636b1176ef0d9a0.tar.gz |
percpu-refcount: use RCU-sched insted of normal RCU
percpu-refcount was incorrectly using preempt_disable/enable() for RCU
critical sections against call_rcu(). 6a24474da8 ("percpu-refcount:
consistently use plain (non-sched) RCU") fixed it by converting the
preepmtion operations with rcu_read_[un]lock() citing that there isn't
any advantage in using sched-RCU over using the usual one; however,
rcu_read_[un]lock() for the preemptible RCU implementation -
CONFIG_TREE_PREEMPT_RCU, chosen when CONFIG_PREEMPT - are slightly
more expensive than preempt_disable/enable().
In a contrived microbench which repeats the followings,
- percpu_ref_get()
- copy 32 bytes of data into percpu buffer
- percpu_put_get()
- copy 32 bytes of data into percpu buffer
rcu_read_[un]lock() used in percpu_ref_get/put() makes it go slower by
about 15% when compared to using sched-RCU.
As the RCU critical sections are extremely short, using sched-RCU
shouldn't have any latency implications. Convert to RCU-sched.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Kent Overstreet <koverstreet@google.com>
Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'COPYING')
0 files changed, 0 insertions, 0 deletions