Messages in this thread | | | Date | Mon, 16 Oct 2023 23:18:09 +0800 | Subject | Re: [PATCH v10 3/5] kprobes: kretprobe scalability improvement with objpool | From | "wuqiang.matt" <> |
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On 2023/10/16 21:21, Masami Hiramatsu (Google) wrote: > On Sun, 15 Oct 2023 13:32:49 +0800 > "wuqiang.matt" <wuqiang.matt@bytedance.com> wrote: > >> 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 1514690434 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 336x: >> >> 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 990067903 >> >> Signed-off-by: wuqiang.matt <wuqiang.matt@bytedance.com> >> --- >> include/linux/kprobes.h | 11 ++--- >> include/linux/rethook.h | 16 ++----- >> kernel/kprobes.c | 93 +++++++++++++++++------------------------ >> kernel/trace/fprobe.c | 32 ++++++-------- >> kernel/trace/rethook.c | 90 ++++++++++++++++++--------------------- >> 5 files changed, 98 insertions(+), 144 deletions(-) >> >> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h >> index 85a64cb95d75..365eb092e9c4 100644 >> --- a/include/linux/kprobes.h >> +++ b/include/linux/kprobes.h >> @@ -26,8 +26,7 @@ >> #include <linux/rcupdate.h> >> #include <linux/mutex.h> >> #include <linux/ftrace.h> >> -#include <linux/refcount.h> >> -#include <linux/freelist.h> >> +#include <linux/objpool.h> >> #include <linux/rethook.h> >> #include <asm/kprobes.h> >> >> @@ -141,7 +140,7 @@ static inline bool kprobe_ftrace(struct kprobe *p) >> */ >> struct kretprobe_holder { >> struct kretprobe *rp; >> - refcount_t ref; >> + struct objpool_head pool; >> }; >> >> struct kretprobe { >> @@ -154,7 +153,6 @@ struct kretprobe { >> #ifdef CONFIG_KRETPROBE_ON_RETHOOK >> struct rethook *rh; >> #else >> - struct freelist_head freelist; >> struct kretprobe_holder *rph; >> #endif >> }; >> @@ -165,10 +163,7 @@ struct kretprobe_instance { >> #ifdef CONFIG_KRETPROBE_ON_RETHOOK >> struct rethook_node node; >> #else >> - union { >> - struct freelist_node freelist; >> - struct rcu_head rcu; >> - }; >> + struct rcu_head rcu; >> struct llist_node llist; >> struct kretprobe_holder *rph; >> kprobe_opcode_t *ret_addr; >> diff --git a/include/linux/rethook.h b/include/linux/rethook.h >> index 26b6f3c81a76..ce69b2b7bc35 100644 >> --- a/include/linux/rethook.h >> +++ b/include/linux/rethook.h >> @@ -6,11 +6,10 @@ >> #define _LINUX_RETHOOK_H >> >> #include <linux/compiler.h> >> -#include <linux/freelist.h> >> +#include <linux/objpool.h> >> #include <linux/kallsyms.h> >> #include <linux/llist.h> >> #include <linux/rcupdate.h> >> -#include <linux/refcount.h> >> >> struct rethook_node; >> >> @@ -30,14 +29,12 @@ typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, >> struct rethook { >> void *data; >> rethook_handler_t handler; >> - struct freelist_head pool; >> - refcount_t ref; >> + struct objpool_head pool; >> struct rcu_head rcu; >> }; >> >> /** >> * struct rethook_node - The rethook shadow-stack entry node. >> - * @freelist: The freelist, linked to struct rethook::pool. >> * @rcu: The rcu_head for deferred freeing. >> * @llist: The llist, linked to a struct task_struct::rethooks. >> * @rethook: The pointer to the struct rethook. >> @@ -48,20 +45,16 @@ struct rethook { >> * on each entry of the shadow stack. >> */ >> struct rethook_node { >> - union { >> - struct freelist_node freelist; >> - struct rcu_head rcu; >> - }; >> + struct rcu_head rcu; >> struct llist_node llist; >> struct rethook *rethook; >> unsigned long ret_addr; >> unsigned long frame; >> }; >> >> -struct rethook *rethook_alloc(void *data, rethook_handler_t handler); >> +struct rethook *rethook_alloc(void *data, rethook_handler_t handler, int size, int num); >> void rethook_stop(struct rethook *rh); >> void rethook_free(struct rethook *rh); >> -void rethook_add_node(struct rethook *rh, struct rethook_node *node); >> struct rethook_node *rethook_try_get(struct rethook *rh); >> void rethook_recycle(struct rethook_node *node); >> void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount); >> @@ -98,4 +91,3 @@ void rethook_flush_task(struct task_struct *tk); >> #endif >> >> #endif >> - >> diff --git a/kernel/kprobes.c b/kernel/kprobes.c >> index ca385b61d546..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); >> @@ -2249,24 +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); >> diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c >> index 3b21f4063258..f5bf98e6b2ac 100644 >> --- a/kernel/trace/fprobe.c >> +++ b/kernel/trace/fprobe.c >> @@ -187,9 +187,9 @@ static void fprobe_init(struct fprobe *fp) >> >> static int fprobe_init_rethook(struct fprobe *fp, int num) >> { >> - int i, size; >> + int size; >> >> - if (num < 0) >> + if (num <= 0) >> return -EINVAL; > > Oops, this must be a bugfix. Let me fix it. > >> >> if (!fp->exit_handler) { >> @@ -202,29 +202,21 @@ static int fprobe_init_rethook(struct fprobe *fp, int num) >> size = fp->nr_maxactive; >> else >> size = num * num_possible_cpus() * 2; >> - if (size < 0) >> + if (size <= 0) >> return -E2BIG; > > Here too. > > Except for this point, it looks good to me.
Got it. Would these 2 fixes catch the release window of v6.6 ?
> > Thanks! >
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