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| author |   Paul E. McKenney <paulmck@kernel.org> | 2022-01-27 20:32:05 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2022-04-11 15:52:30 -0700 |
| commit | 9f2e91d94c91558e3764fe4e01c5e6281a90f239 (patch) | |
| tree | b30cc7765fe023030979834882624c951688eeae /include/linux/srcutree.h | |
| parent | srcu: Create concurrency-safe helper for initiating size transition (diff) | |
| download | linux-dev-9f2e91d94c91558e3764fe4e01c5e6281a90f239.tar.xz linux-dev-9f2e91d94c91558e3764fe4e01c5e6281a90f239.zip | |
srcu: Add contention-triggered addition of srcu_node tree
This commit instruments the acquisitions of the srcu_struct structure's
->lock, enabling the initiation of a transition from SRCU_SIZE_SMALL
to SRCU_SIZE_BIG when sufficient contention is experienced. The
instrumentation counts the number of trylock failures within the confines
of a single jiffy. If that number exceeds the value specified by the
srcutree.small_contention_lim kernel boot parameter (which defaults to
100), and if the value specified by the srcutree.convert_to_big kernel
boot parameter has the 0x10 bit set (defaults to 0), then a transition
will be automatically initiated.
By default, there will never be any transitions, so that none of the
srcu_struct structures ever gains an srcu_node array.
The useful values for srcutree.convert_to_big are:
0x00: Never convert.
0x01: Always convert at init_srcu_struct() time.
0x02: Convert when rcutorture prints its first round of statistics.
0x03: Decide conversion approach at boot given system size.
0x10: Convert if contention is encountered.
0x12: Convert if contention is encountered or when rcutorture prints
its first round of statistics, whichever comes first.
The value 0x11 acts the same as 0x01 because the conversion happens
before there is any chance of contention.
[ paulmck: Apply "static" feedback from kernel test robot. ]
Co-developed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'include/linux/srcutree.h')
| -rw-r--r-- | include/linux/srcutree.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 44bd204498a1..1b9ff4ed37e4 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -72,6 +72,8 @@ struct srcu_struct { 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) */ + unsigned long srcu_size_jiffies; /* Current contention-measurement interval. */ + unsigned long srcu_n_lock_retries; /* Contention events in current interval. */ struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */ bool sda_is_static; /* May ->sda be passed to free_percpu()? */ unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */ |