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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-10-01 10:26:24 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-12-04 12:26:52 -0800 |
| commit | df5bd5144a80a9f6c3807383b11f735dae9caf9d (patch) | |
| tree | fce44d0970a70446c5fd6b50f2e764db0efb8e56 /kernel/rcu/tree.h | |
| parent | 1307f2148719cc9e9d12f5fa7d5b3b61ec5aef72 (diff) | |
| download | linux-df5bd5144a80a9f6c3807383b11f735dae9caf9d.tar.gz linux-df5bd5144a80a9f6c3807383b11f735dae9caf9d.tar.bz2 linux-df5bd5144a80a9f6c3807383b11f735dae9caf9d.zip | |
rcu: Reduce expedited GP memory contention via per-CPU variables
Currently, the piggybacked-work checks carried out by sync_exp_work_done()
atomically increment a small set of variables (the ->expedited_workdone0,
->expedited_workdone1, ->expedited_workdone2, ->expedited_workdone3
fields in the rcu_state structure), which will form a memory-contention
bottleneck given a sufficiently large number of CPUs concurrently invoking
either synchronize_rcu_expedited() or synchronize_sched_expedited().
This commit therefore moves these for fields to the per-CPU rcu_data
structure, eliminating the memory contention. The show_rcuexp() function
also changes to sum up each field in the rcu_data structures.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/tree.h')
| -rw-r--r-- | kernel/rcu/tree.h | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 8151971a8978..6cbec31f99d6 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -386,6 +386,10 @@ struct rcu_data { struct rcu_head oom_head; #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ struct mutex exp_funnel_mutex; + atomic_long_t expedited_workdone0; /* # done by others #0. */ + atomic_long_t expedited_workdone1; /* # done by others #1. */ + atomic_long_t expedited_workdone2; /* # done by others #2. */ + atomic_long_t expedited_workdone3; /* # done by others #3. */ /* 7) Callback offloading. */ #ifdef CONFIG_RCU_NOCB_CPU @@ -500,10 +504,6 @@ struct rcu_state { /* End of fields guarded by barrier_mutex. */ unsigned long expedited_sequence; /* Take a ticket. */ - atomic_long_t expedited_workdone0; /* # done by others #0. */ - atomic_long_t expedited_workdone1; /* # done by others #1. */ - atomic_long_t expedited_workdone2; /* # done by others #2. */ - atomic_long_t expedited_workdone3; /* # done by others #3. */ atomic_long_t expedited_normal; /* # fallbacks to normal. */ atomic_t expedited_need_qs; /* # CPUs left to check in. */ wait_queue_head_t expedited_wq; /* Wait for check-ins. */ |