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| author | Paul E. McKenney <paulmck@kernel.org> | 2022-01-31 11:21:30 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2022-05-03 10:19:39 -0700 |
| commit | a57ffb3c6b67e59e8632f731414b792eacc6cca0 (patch) | |
| tree | 34d09d000fabf5eacfed74c7e5cd23a5959ddb70 /kernel/rcu/srcutree.c | |
| parent | 9f2e91d94c91558e3764fe4e01c5e6281a90f239 (diff) | |
| download | lwn-a57ffb3c6b67e59e8632f731414b792eacc6cca0.tar.gz lwn-a57ffb3c6b67e59e8632f731414b792eacc6cca0.zip | |
srcu: Automatically determine size-transition strategy at boot
This commit adds a srcutree.convert_to_big option of zero that causes
SRCU to decide at boot whether to wait for contention (small systems) or
immediately expand to large (large systems). A new srcutree.big_cpu_lim
(defaulting to 128) defines how many CPUs constitute a large system.
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 'kernel/rcu/srcutree.c')
| -rw-r--r-- | kernel/rcu/srcutree.c | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 0bc6a0a3edee..b9dec26245e0 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -41,10 +41,10 @@ module_param(counter_wrap_check, ulong, 0444); /* * Control conversion to SRCU_SIZE_BIG: - * 0: Don't convert at all (default). + * 0: Don't convert at all. * 1: Convert at init_srcu_struct() time. * 2: Convert when rcutorture invokes srcu_torture_stats_print(). - * 3: Decide at boot time based on system shape. + * 3: Decide at boot time based on system shape (default). * 0x1x: Convert when excessive contention encountered. */ #define SRCU_SIZING_NONE 0 @@ -57,9 +57,13 @@ module_param(counter_wrap_check, ulong, 0444); #define SRCU_SIZING_IS_INIT() (SRCU_SIZING_IS(SRCU_SIZING_INIT)) #define SRCU_SIZING_IS_TORTURE() (SRCU_SIZING_IS(SRCU_SIZING_TORTURE)) #define SRCU_SIZING_IS_CONTEND() (convert_to_big & SRCU_SIZING_CONTEND) -static int convert_to_big = SRCU_SIZING_NONE; +static int convert_to_big = SRCU_SIZING_AUTO; module_param(convert_to_big, int, 0444); +/* Number of CPUs to trigger init_srcu_struct()-time transition to big. */ +static int big_cpu_lim __read_mostly = 128; +module_param(big_cpu_lim, int, 0444); + /* Contention events per jiffy to initiate transition to big. */ static int small_contention_lim __read_mostly = 100; module_param(small_contention_lim, int, 0444); @@ -1619,6 +1623,17 @@ void __init srcu_init(void) { struct srcu_struct *ssp; + /* Decide on srcu_struct-size strategy. */ + if (SRCU_SIZING_IS(SRCU_SIZING_AUTO)) { + if (nr_cpu_ids >= big_cpu_lim) { + convert_to_big = SRCU_SIZING_INIT; // Don't bother waiting for contention. + pr_info("%s: Setting srcu_struct sizes to big.\n", __func__); + } else { + convert_to_big = SRCU_SIZING_NONE | SRCU_SIZING_CONTEND; + pr_info("%s: Setting srcu_struct sizes based on contention.\n", __func__); + } + } + /* * Once that is set, call_srcu() can follow the normal path and * queue delayed work. This must follow RCU workqueues creation @@ -1629,6 +1644,8 @@ void __init srcu_init(void) ssp = list_first_entry(&srcu_boot_list, struct srcu_struct, work.work.entry); list_del_init(&ssp->work.work.entry); + if (SRCU_SIZING_IS(SRCU_SIZING_INIT) && ssp->srcu_size_state == SRCU_SIZE_SMALL) + ssp->srcu_size_state = SRCU_SIZE_ALLOC; queue_work(rcu_gp_wq, &ssp->work.work); } } |