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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-04-26 00:03:11 +0300 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-04-27 02:32:17 +0300 |
| commit | 22607d66bbc3e81140d3bcf08894f4378eb36428 (patch) | |
| tree | 88b0caa1cd8bfa66e6a4b00ad21108f03369eb03 /include | |
| parent | 2da4b2a7fd8de52c44fa83c59f00d38a0d90caae (diff) | |
| download | linux-22607d66bbc3e81140d3bcf08894f4378eb36428.tar.xz | |
srcu: Specify auto-expedite holdoff time
On small systems, in the absence of readers, expedited SRCU grace
periods can complete in less than a microsecond. This means that an
eight-CPU system can have all CPUs doing synchronize_srcu() in a tight
loop and almost always expedite. This might actually be desirable in
some situations, but in general it is a good way to needlessly burn
CPU cycles. And in those situations where it is desirable, your friend
is the function synchronize_srcu_expedited().
For other situations, this commit adds a kernel parameter that specifies
a holdoff between completing the last SRCU grace period and auto-expediting
the next. If the next grace period starts before the holdoff expires,
auto-expediting is disabled. The holdoff is 50 microseconds by default,
and can be tuned to the desired number of nanoseconds. A value of zero
disables auto-expediting.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Mike Galbraith <efault@gmx.de>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/srcutree.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 86df48d3e97b..32e86d85fd11 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -84,6 +84,7 @@ struct srcu_struct { unsigned long srcu_gp_seq; /* Grace-period seq #. */ unsigned long srcu_gp_seq_needed; /* Latest gp_seq needed. */ unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */ + unsigned long srcu_last_gp_end; /* Last GP end timestamp (ns) */ struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */ unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */ struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */ |