From 4bbd9345565933823f38a419df65661f12adbe5e Mon Sep 17 00:00:00 2001 From: "wuqiang.matt" Date: Tue, 17 Oct 2023 21:56:52 +0800 Subject: kprobes: kretprobe scalability improvement kretprobe is using freelist to manage return-instances, but freelist, as LIFO queue based on singly linked list, scales badly and reduces the overall throughput of kretprobed routines, especially for high contention scenarios. Here's a typical throughput test of sys_prctl (counts in 10 seconds, measured with perf stat -a -I 10000 -e syscalls:sys_enter_prctl): OS: Debian 10 X86_64, Linux 6.5rc7 with freelist HW: XEON 8336C x 2, 64 cores/128 threads, DDR4 3200MT/s 1T 2T 4T 8T 16T 24T 24150045 29317964 15446741 12494489 18287272 17708768 32T 48T 64T 72T 96T 128T 16200682 13737658 11645677 11269858 10470118 9931051 This patch introduces objpool to replace freelist. objpool is a high performance queue, which can bring near-linear scalability to kretprobed routines. Tests of kretprobe throughput show the biggest ratio as 159x of original freelist. Here's the result: 1T 2T 4T 8T 16T native: 41186213 82336866 164250978 328662645 658810299 freelist: 24150045 29317964 15446741 12494489 18287272 objpool: 23926730 48010314 96125218 191782984 385091769 32T 48T 64T 96T 128T native: 1330338351 1969957941 2512291791 2615754135 2671040914 freelist: 16200682 13737658 11645677 10470118 9931051 objpool: 764481096 1147149781 1456220214 1502109662 1579015050 Testings on 96-core ARM64 output similarly, but with the biggest ratio up to 448x: OS: Debian 10 AARCH64, Linux 6.5rc7 HW: Kunpeng-920 96 cores/2 sockets/4 NUMA nodes, DDR4 2933 MT/s 1T 2T 4T 8T 16T native: . 30066096 63569843 126194076 257447289 505800181 freelist: 16152090 11064397 11124068 7215768 5663013 objpool: 13997541 28032100 55726624 110099926 221498787 24T 32T 48T 64T 96T native: 763305277 1015925192 1521075123 2033009392 3021013752 freelist: 5015810 4602893 3766792 3382478 2945292 objpool: 328192025 439439564 668534502 887401381 1319972072 Link: https://lore.kernel.org/all/20231017135654.82270-4-wuqiang.matt@bytedance.com/ Signed-off-by: wuqiang.matt Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google) --- kernel/kprobes.c | 91 ++++++++++++++++++++++++-------------------------------- 1 file changed, 39 insertions(+), 52 deletions(-) (limited to 'kernel/kprobes.c') diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 0c6185aefaef..075a632e6c7c 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1877,13 +1877,27 @@ static struct notifier_block kprobe_exceptions_nb = { #ifdef CONFIG_KRETPROBES #if !defined(CONFIG_KRETPROBE_ON_RETHOOK) + +/* callbacks for objpool of kretprobe instances */ +static int kretprobe_init_inst(void *nod, void *context) +{ + struct kretprobe_instance *ri = nod; + + ri->rph = context; + return 0; +} +static int kretprobe_fini_pool(struct objpool_head *head, void *context) +{ + kfree(context); + return 0; +} + static void free_rp_inst_rcu(struct rcu_head *head) { struct kretprobe_instance *ri = container_of(head, struct kretprobe_instance, rcu); + struct kretprobe_holder *rph = ri->rph; - if (refcount_dec_and_test(&ri->rph->ref)) - kfree(ri->rph); - kfree(ri); + objpool_drop(ri, &rph->pool); } NOKPROBE_SYMBOL(free_rp_inst_rcu); @@ -1892,7 +1906,7 @@ static void recycle_rp_inst(struct kretprobe_instance *ri) struct kretprobe *rp = get_kretprobe(ri); if (likely(rp)) - freelist_add(&ri->freelist, &rp->freelist); + objpool_push(ri, &rp->rph->pool); else call_rcu(&ri->rcu, free_rp_inst_rcu); } @@ -1929,23 +1943,12 @@ NOKPROBE_SYMBOL(kprobe_flush_task); static inline void free_rp_inst(struct kretprobe *rp) { - struct kretprobe_instance *ri; - struct freelist_node *node; - int count = 0; - - node = rp->freelist.head; - while (node) { - ri = container_of(node, struct kretprobe_instance, freelist); - node = node->next; - - kfree(ri); - count++; - } + struct kretprobe_holder *rph = rp->rph; - if (refcount_sub_and_test(count, &rp->rph->ref)) { - kfree(rp->rph); - rp->rph = NULL; - } + if (!rph) + return; + rp->rph = NULL; + objpool_fini(&rph->pool); } /* This assumes the 'tsk' is the current task or the is not running. */ @@ -2087,19 +2090,17 @@ NOKPROBE_SYMBOL(__kretprobe_trampoline_handler) static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs) { struct kretprobe *rp = container_of(p, struct kretprobe, kp); + struct kretprobe_holder *rph = rp->rph; struct kretprobe_instance *ri; - struct freelist_node *fn; - fn = freelist_try_get(&rp->freelist); - if (!fn) { + ri = objpool_pop(&rph->pool); + if (!ri) { rp->nmissed++; return 0; } - ri = container_of(fn, struct kretprobe_instance, freelist); - if (rp->entry_handler && rp->entry_handler(ri, regs)) { - freelist_add(&ri->freelist, &rp->freelist); + objpool_push(ri, &rph->pool); return 0; } @@ -2193,7 +2194,6 @@ int kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long o int register_kretprobe(struct kretprobe *rp) { int ret; - struct kretprobe_instance *inst; int i; void *addr; @@ -2227,19 +2227,12 @@ int register_kretprobe(struct kretprobe *rp) rp->maxactive = max_t(unsigned int, 10, 2*num_possible_cpus()); #ifdef CONFIG_KRETPROBE_ON_RETHOOK - rp->rh = rethook_alloc((void *)rp, kretprobe_rethook_handler); - if (!rp->rh) - return -ENOMEM; + rp->rh = rethook_alloc((void *)rp, kretprobe_rethook_handler, + sizeof(struct kretprobe_instance) + + rp->data_size, rp->maxactive); + if (IS_ERR(rp->rh)) + return PTR_ERR(rp->rh); - for (i = 0; i < rp->maxactive; i++) { - inst = kzalloc(struct_size(inst, data, rp->data_size), GFP_KERNEL); - if (inst == NULL) { - rethook_free(rp->rh); - rp->rh = NULL; - return -ENOMEM; - } - rethook_add_node(rp->rh, &inst->node); - } rp->nmissed = 0; /* Establish function entry probe point */ ret = register_kprobe(&rp->kp); @@ -2248,24 +2241,18 @@ int register_kretprobe(struct kretprobe *rp) rp->rh = NULL; } #else /* !CONFIG_KRETPROBE_ON_RETHOOK */ - rp->freelist.head = NULL; rp->rph = kzalloc(sizeof(struct kretprobe_holder), GFP_KERNEL); if (!rp->rph) return -ENOMEM; - rp->rph->rp = rp; - for (i = 0; i < rp->maxactive; i++) { - inst = kzalloc(struct_size(inst, data, rp->data_size), GFP_KERNEL); - if (inst == NULL) { - refcount_set(&rp->rph->ref, i); - free_rp_inst(rp); - return -ENOMEM; - } - inst->rph = rp->rph; - freelist_add(&inst->freelist, &rp->freelist); + if (objpool_init(&rp->rph->pool, rp->maxactive, rp->data_size + + sizeof(struct kretprobe_instance), GFP_KERNEL, + rp->rph, kretprobe_init_inst, kretprobe_fini_pool)) { + kfree(rp->rph); + rp->rph = NULL; + return -ENOMEM; } - refcount_set(&rp->rph->ref, i); - + rp->rph->rp = rp; rp->nmissed = 0; /* Establish function entry probe point */ ret = register_kprobe(&rp->kp); -- cgit v1.2.3