This commit adds an srcu_tree.convert_to_big kernel parameter that either refuses to convert at all (0), converts immediately at init_srcu_struct() time (1), or lets rcutorture convert it (2). An addition contention-based dynamic convertion choice will be added, along with documentation. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> --- kernel/rcu/srcutree.c | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 550991cc213d3..d1f1ff930acf5 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -39,6 +39,15 @@ module_param(exp_holdoff, ulong, 0444); static ulong counter_wrap_check = (ULONG_MAX >> 2); module_param(counter_wrap_check, ulong, 0444); +/* + * Control conversion to SRCU_SIZE_BIG: + * 0: Don't convert at all (default). + * 1: Convert at init_srcu_struct() time. + * 2: Convert when rcutorture invokes srcu_torture_stats_print(). + */ +static int convert_to_big; +module_param(convert_to_big, int, 0444); + /* Early-boot callback-management, so early that no lock is required! */ static LIST_HEAD(srcu_boot_list); static bool __read_mostly srcu_init_done; @@ -113,7 +122,7 @@ static void init_srcu_struct_data(struct srcu_struct *ssp) * Allocated and initialize SRCU combining tree. Returns @true if * allocation succeeded and @false otherwise. */ -static bool init_srcu_struct_nodes(struct srcu_struct *ssp) +static bool init_srcu_struct_nodes(struct srcu_struct *ssp, gfp_t gfp_flags) { int cpu; int i; @@ -125,7 +134,7 @@ static bool init_srcu_struct_nodes(struct srcu_struct *ssp) /* Initialize geometry if it has not already been initialized. */ rcu_init_geometry(); - ssp->node = kcalloc(rcu_num_nodes, sizeof(*ssp->node), GFP_ATOMIC); + ssp->node = kcalloc(rcu_num_nodes, sizeof(*ssp->node), gfp_flags); if (!ssp->node) return false; @@ -204,6 +213,16 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static) init_srcu_struct_data(ssp); ssp->srcu_gp_seq_needed_exp = 0; ssp->srcu_last_gp_end = ktime_get_mono_fast_ns(); + if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && convert_to_big == 1) { + if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC)) { + if (!is_static) { + free_percpu(ssp->sda); + ssp->sda = NULL; + } + return -ENOMEM; + } + WRITE_ONCE(ssp->srcu_size_state, SRCU_SIZE_BIG); + } smp_store_release(&ssp->srcu_gp_seq_needed, 0); /* Init done. */ return 0; } @@ -627,7 +646,7 @@ static void srcu_gp_end(struct srcu_struct *ssp) ss_state = smp_load_acquire(&ssp->srcu_size_state); if (ss_state && ss_state != SRCU_SIZE_BIG) { if (ss_state == SRCU_SIZE_ALLOC) - init_srcu_struct_nodes(ssp); + init_srcu_struct_nodes(ssp, GFP_KERNEL); else smp_store_release(&ssp->srcu_size_state, ss_state + 1); } @@ -1456,6 +1475,8 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf) s1 += c1; } pr_cont(" T(%ld,%ld)\n", s0, s1); + if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && convert_to_big == 2) + WRITE_ONCE(ssp->srcu_size_state, SRCU_SIZE_ALLOC); } EXPORT_SYMBOL_GPL(srcu_torture_stats_print); -- 2.31.1.189.g2e36527f23