diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 13 | ||||
| -rw-r--r-- | kernel/rcu/srcutree.c | 48 |
2 files changed, 45 insertions, 16 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 3f1cc5e317ed..1f1fcac7777d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5608,6 +5608,19 @@ off: Disable mitigation and remove performance impact to RDRAND and RDSEED + srcutree.convert_to_big [KNL] + Specifies under what conditions an SRCU tree + srcu_struct structure will be converted to big + form, that is, with an rcu_node tree: + + 0: Never. + 1: At init_srcu_struct() time. + 2: When rcutorture decides to. + + Either way, the srcu_node tree will be sized based + on the actual runtime number of CPUs (nr_cpu_ids) + instead of the compile-time CONFIG_NR_CPUS. + srcutree.counter_wrap_check [KNL] Specifies how frequently to check for grace-period sequence counter wrap for the diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 2e7ed67646db..9dd048989027 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; @@ -123,7 +132,7 @@ static inline bool srcu_invl_snp_seq(unsigned long s) * 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; @@ -135,7 +144,7 @@ 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; @@ -213,17 +222,19 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static) if (!ssp->sda) return -ENOMEM; init_srcu_struct_data(ssp); - if (!init_srcu_struct_nodes(ssp)) { - if (!is_static) { - free_percpu(ssp->sda); - ssp->sda = NULL; - return -ENOMEM; - } - } else { - ssp->srcu_size_state = SRCU_SIZE_BIG; - } 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; + } + } else { + WRITE_ONCE(ssp->srcu_size_state, SRCU_SIZE_BIG); + } + } smp_store_release(&ssp->srcu_gp_seq_needed, 0); /* Init done. */ return 0; } @@ -594,7 +605,8 @@ static void srcu_gp_end(struct srcu_struct *ssp) /* A new grace period can start at this point. But only one. */ /* Initiate callback invocation as needed. */ - if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER) { + ss_state = smp_load_acquire(&ssp->srcu_size_state); + if (ss_state < SRCU_SIZE_WAIT_BARRIER) { srcu_schedule_cbs_sdp(per_cpu_ptr(ssp->sda, 0), cbdelay); } else { idx = rcu_seq_ctr(gpseq) % ARRAY_SIZE(snp->srcu_have_cbs); @@ -603,13 +615,16 @@ static void srcu_gp_end(struct srcu_struct *ssp) cbs = false; last_lvl = snp >= ssp->level[rcu_num_lvls - 1]; if (last_lvl) - cbs = snp->srcu_have_cbs[idx] == gpseq; + cbs = ss_state < SRCU_SIZE_BIG || snp->srcu_have_cbs[idx] == gpseq; snp->srcu_have_cbs[idx] = gpseq; rcu_seq_set_state(&snp->srcu_have_cbs[idx], 1); sgsne = snp->srcu_gp_seq_needed_exp; if (srcu_invl_snp_seq(sgsne) || ULONG_CMP_LT(sgsne, gpseq)) WRITE_ONCE(snp->srcu_gp_seq_needed_exp, gpseq); - mask = snp->srcu_data_have_cbs[idx]; + if (ss_state < SRCU_SIZE_BIG) + mask = ~0; + else + mask = snp->srcu_data_have_cbs[idx]; snp->srcu_data_have_cbs[idx] = 0; spin_unlock_irq_rcu_node(snp); if (cbs) @@ -645,10 +660,9 @@ static void srcu_gp_end(struct srcu_struct *ssp) } /* Transition to big if needed. */ - ss_state = smp_load_acquire(&ssp->srcu_size_state); if (ss_state != SRCU_SIZE_SMALL && 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); } @@ -1494,6 +1508,8 @@ 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); |