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| author |   Paul E. McKenney <paulmck@kernel.org> | 2020-08-05 17:25:23 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-08-24 18:40:24 -0700 |
| commit | aecd34b9765de3b58c98a1d75b982fc64becd1e9 (patch) | |
| tree | e24b28222c483c0fdcb19a4ef2d6e4cc291b5d9a /kernel/rcu | |
| parent | rcu: Reduce leaf fanout for strict RCU grace periods (diff) | |
| download | linux-dev-aecd34b9765de3b58c98a1d75b982fc64becd1e9.tar.xz linux-dev-aecd34b9765de3b58c98a1d75b982fc64becd1e9.zip | |
rcu: Restrict default jiffies_till_first_fqs for strict RCU GPs
If there are idle CPUs, RCU's grace-period kthread will wait several
jiffies before even thinking about polling them. This promotes
efficiency, which is normally a good thing, but when the kernel
has been built with CONFIG_RCU_STRICT_GRACE_PERIOD=y, we care more
about short grace periods. This commit therefore restricts the
default jiffies_till_first_fqs value to zero in kernels built with
CONFIG_RCU_STRICT_GRACE_PERIOD=y, which causes RCU's grace-period kthread
to poll for idle CPUs immediately after starting a grace period.
Reported-by Jann Horn <jannh@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8ce77d9ac716..85511590fc38 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -485,7 +485,7 @@ module_param(qhimark, long, 0444); module_param(qlowmark, long, 0444); module_param(qovld, long, 0444); -static ulong jiffies_till_first_fqs = ULONG_MAX; +static ulong jiffies_till_first_fqs = IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 0 : ULONG_MAX; static ulong jiffies_till_next_fqs = ULONG_MAX; static bool rcu_kick_kthreads; static int rcu_divisor = 7; |