Messages in this thread | | | Date | Wed, 28 Dec 2022 00:59:35 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH v7 3/5] kprobes: kretprobe scalability improvement with objpool |
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Hi Matt,
On Mon, 12 Dec 2022 20:31:51 +0800 wuqiang <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_flock (counts in 10 seconds, > measured with perf stat -a -I 10000 -e syscalls:sys_enter_flock): > > OS: Debian 10 X86_64, Linux 6.1rc2 > HW: XEON 8336C x 2, 64 cores/128 threads, DDR4 3200MT/s > > 1X 2X 4X 6X 8X 12X 16X > 34762430 36546920 17949900 13101899 12569595 12646601 14729195 > 24X 32X 48X 64X 72X 96X 128X > 19263546 10102064 8985418 11936495 11493980 7127789 9330985 > > This patch introduces objpool to kretprobe and rethook, with orginal > freelist replaced and brings near-linear scalability to kretprobed > routines. Tests of kretprobe throughput show the biggest ratio as > 333.9x of the original freelist. Here's the comparison: > > 1X 2X 4X 8X 16X > freelist: 34762430 36546920 17949900 12569595 14729195 > objpool: 35627544 72182095 144068494 287564688 576903916 > 32X 48X 64X 96X 128X > freelist: 10102064 8985418 11936495 7127789 9330985 > objpool: 1158876372 1737828164 2324371724 2380310472 2463182819 > > Tests on 96-core ARM64 system output similarly, but with the biggest > ratio up to 642.2x: > > OS: Debian 10 AARCH64, Linux 6.1rc2 > HW: Kunpeng-920 96 cores/2 sockets/4 NUMA nodes, DDR4 2933 MT/s > > 1X 2X 4X 8X 16X > freelist: 17498299 10887037 10224710 8499132 6421751 > objpool: 18715726 35549845 71615884 144258971 283707220 > 24X 32X 48X 64X 96X > freelist: 5339868 4819116 3593919 3121575 2687167 > objpool: 419830913 571609748 877456139 1143316315 1725668029
So for x86, the rethook is applied. And for arm64, kretprobes is applied. OK, Looks good to me.
I have some comments below (but just nitpicks.)
> > Signed-off-by: wuqiang <wuqiang.matt@bytedance.com>
BTW, can you clarify your name on Signed-off-by? I see your name on [5/5] that says "Matt Wu <wuqiang.matt@bytedance.com>". It should be the same on Signed-off-by (and MODULE_AUTHOR) so that we can make sure it is you.
> --- > include/linux/kprobes.h | 9 ++-- > include/linux/rethook.h | 14 ++---- > kernel/kprobes.c | 101 +++++++++++++++++++--------------------- > kernel/trace/fprobe.c | 37 ++++++--------- > kernel/trace/rethook.c | 99 ++++++++++++++++++++------------------- > 5 files changed, 118 insertions(+), 142 deletions(-) > > diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h > index a0b92be98984..122b1f21f3a9 100644 > --- a/include/linux/kprobes.h > +++ b/include/linux/kprobes.h > @@ -27,7 +27,7 @@ > #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> > > @@ -141,6 +141,7 @@ static inline bool kprobe_ftrace(struct kprobe *p) > */ > struct kretprobe_holder { > struct kretprobe *rp; > + struct objpool_head pool; > refcount_t ref; > }; > > @@ -154,7 +155,6 @@ struct kretprobe { > #ifdef CONFIG_KRETPROBE_ON_RETHOOK > struct rethook *rh; > #else > - struct freelist_head freelist; > struct kretprobe_holder *rph; > #endif > }; > @@ -165,10 +165,7 @@ 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 c8ac1e5afcd1..f97283c622b7 100644 > --- a/include/linux/rethook.h > +++ b/include/linux/rethook.h > @@ -6,7 +6,7 @@ > #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> > @@ -30,14 +30,13 @@ typedef void (*rethook_handler_t) (struct rethook_node *, void *, struct pt_regs > struct rethook { > void *data; > rethook_handler_t handler; > - struct freelist_head pool; > + struct objpool_head pool; > refcount_t ref; > 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. > @@ -48,19 +47,15 @@ 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_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); > @@ -97,4 +92,3 @@ void rethook_flush_task(struct task_struct *tk); > #endif > > #endif > - > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 3050631e528d..5f35997b61f7 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1868,13 +1868,28 @@ 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); > + if (refcount_dec_and_test(&rph->ref)) > + objpool_fini(&rph->pool); > } > NOKPROBE_SYMBOL(free_rp_inst_rcu); > > @@ -1883,7 +1898,7 @@ 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); > } > @@ -1920,23 +1935,18 @@ 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; > + void *nod; > > - if (refcount_sub_and_test(count, &rp->rph->ref)) { > - kfree(rp->rph); > - rp->rph = NULL; > - } > + rp->rph = NULL; > + do { > + nod = objpool_pop(&rph->pool); > + /* deref anyway since we've one extra ref grabbed */ > + if (refcount_dec_and_test(&rph->ref)) { > + objpool_fini(&rph->pool); > + break; > + } > + } while (nod); > } > > /* This assumes the 'tsk' is the current task or the is not running. */ > @@ -2078,19 +2088,17 @@ 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; > } > > @@ -2183,7 +2191,6 @@ 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; > > @@ -2221,20 +2228,12 @@ int register_kretprobe(struct kretprobe *rp) > #endif > } > #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(sizeof(struct kretprobe_instance) + > - 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); > @@ -2243,25 +2242,19 @@ 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(sizeof(struct kretprobe_instance) + > - 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); > - > + refcount_set(&rp->rph->ref, rp->maxactive + 1); > + 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 e8143e368074..9b685d6921d1 100644 > --- a/kernel/trace/fprobe.c > +++ b/kernel/trace/fprobe.c > @@ -125,41 +125,32 @@ static void fprobe_init(struct fprobe *fp) > > static int fprobe_init_rethook(struct fprobe *fp, int num) > { > - int i, size; > - > - if (num < 0) > - return -EINVAL; > + int max; > > if (!fp->exit_handler) { > fp->rethook = NULL; > return 0; > } > > - /* Initialize rethook if needed */ > - size = num * num_possible_cpus() * 2; > - if (size < 0) > + if (num <= 0) > + return -EINVAL; > + max = num * num_possible_cpus() * 2; > + /* Fail if max overflows */ > + if (max <= 0) > return -E2BIG; > > - fp->rethook = rethook_alloc((void *)fp, fprobe_exit_handler); > - if (!fp->rethook) > - return -ENOMEM; > - for (i = 0; i < size; i++) { > - struct fprobe_rethook_node *node; > - > - node = kzalloc(sizeof(*node), GFP_KERNEL); > - if (!node) { > - rethook_free(fp->rethook); > - fp->rethook = NULL; > - return -ENOMEM; > - } > - rethook_add_node(fp->rethook, &node->node); > - } > + /* Initialize rethook */ > + fp->rethook = rethook_alloc((void *)fp, fprobe_exit_handler, > + sizeof(struct fprobe_rethook_node), max); > + if (IS_ERR(fp->rethook)) > + return PTR_ERR(fp->rethook); > + > return 0; > } > > static void fprobe_fail_cleanup(struct fprobe *fp) > { > - if (fp->rethook) { > + if (!IS_ERR_OR_NULL(fp->rethook)) { > /* Don't need to cleanup rethook->handler because this is not used. */ > rethook_free(fp->rethook); > fp->rethook = NULL; > @@ -313,7 +304,7 @@ int unregister_fprobe(struct fprobe *fp) > * current running handlers are finished, call unregister_ftrace_function() > * after this. > */ > - if (fp->rethook) > + if (!IS_ERR_OR_NULL(fp->rethook)) > rethook_free(fp->rethook); > > ret = unregister_ftrace_function(&fp->ops); > diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c > index 32c3dfdb4d6a..6e1014e4f2f7 100644 > --- a/kernel/trace/rethook.c > +++ b/kernel/trace/rethook.c > @@ -36,21 +36,16 @@ void rethook_flush_task(struct task_struct *tk) > static void rethook_free_rcu(struct rcu_head *head) > { > struct rethook *rh = container_of(head, struct rethook, rcu); > - struct rethook_node *rhn; > - struct freelist_node *node; > - int count = 1; > - > - node = rh->pool.head; > - while (node) { > - rhn = container_of(node, struct rethook_node, freelist); > - node = node->next; > - kfree(rhn); > - count++; > - } > + struct rethook_node *nod;
Why 'nod' but not 'node'?
> > - /* The rh->ref is the number of pooled node + 1 */ > - if (refcount_sub_and_test(count, &rh->ref)) > - kfree(rh); > + do { > + nod = objpool_pop(&rh->pool); > + /* deref anyway since we've one extra ref grabbed */ > + if (refcount_dec_and_test(&rh->ref)) { > + objpool_fini(&rh->pool); > + break; > + } > + } while (nod); > } > > /** > @@ -70,54 +65,65 @@ void rethook_free(struct rethook *rh) > call_rcu(&rh->rcu, rethook_free_rcu); > } > > +static int rethook_init_node(void *nod, void *context) > +{ > + struct rethook_node *node = nod; > + > + node->rethook = context; > + return 0; > +} > + > +static int rethook_fini_pool(struct objpool_head *head, void *context) > +{ > + kfree(context); > + return 0; > +} > + > /** > * rethook_alloc() - Allocate struct rethook. > * @data: a data to pass the @handler when hooking the return. > - * @handler: the return hook callback function. > + * @handler: the return hook callback function, must NOT be NULL > + * @gfp: default gfp for objpool allocation
There is no @gfp in the function arguments.
> + * @size: node size: rethook node and additional data > + * @num: number of rethook nodes to be preallocated > * > * Allocate and initialize a new rethook with @data and @handler. > - * Return NULL if memory allocation fails or @handler is NULL. > + * Return pointer of new rethook, or error codes for failures. > + * > * Note that @handler == NULL means this rethook is going to be freed. > */ > -struct rethook *rethook_alloc(void *data, rethook_handler_t handler) > +struct rethook *rethook_alloc(void *data, rethook_handler_t handler, > + int size, int num) > { > - struct rethook *rh = kzalloc(sizeof(struct rethook), GFP_KERNEL); > + struct rethook *rh; > > - if (!rh || !handler) { > - kfree(rh); > - return NULL; > - } > + if (!handler || num <= 0 || size < sizeof(struct rethook_node)) > + return ERR_PTR(-EINVAL); > + > + rh = kzalloc(sizeof(struct rethook), GFP_KERNEL); > + if (!rh) > + return ERR_PTR(-ENOMEM); > > rh->data = data; > rh->handler = handler; > - rh->pool.head = NULL; > - refcount_set(&rh->ref, 1); > > + /* initialize the objpool for rethook nodes */ > + if (objpool_init(&rh->pool, num, size, GFP_KERNEL, rh, > + rethook_init_node, rethook_fini_pool)) { > + kfree(rh); > + return ERR_PTR(-ENOMEM); > + } > + refcount_set(&rh->ref, num + 1); > return rh; > } > > -/** > - * rethook_add_node() - Add a new node to the rethook. > - * @rh: the struct rethook. > - * @node: the struct rethook_node to be added. > - * > - * Add @node to @rh. User must allocate @node (as a part of user's > - * data structure.) The @node fields are initialized in this function. > - */ > -void rethook_add_node(struct rethook *rh, struct rethook_node *node) > -{ > - node->rethook = rh; > - freelist_add(&node->freelist, &rh->pool); > - refcount_inc(&rh->ref); > -} > - > static void free_rethook_node_rcu(struct rcu_head *head) > { > struct rethook_node *node = container_of(head, struct rethook_node, rcu); > + struct rethook *rh = node->rethook; > > - if (refcount_dec_and_test(&node->rethook->ref)) > - kfree(node->rethook); > - kfree(node); > + if (refcount_dec_and_test(&rh->ref)) > + objpool_fini(&rh->pool); > } > > /** > @@ -132,7 +138,7 @@ void rethook_recycle(struct rethook_node *node) > lockdep_assert_preemption_disabled(); > > if (likely(READ_ONCE(node->rethook->handler))) > - freelist_add(&node->freelist, &node->rethook->pool); > + objpool_push(node, &node->rethook->pool); > else > call_rcu(&node->rcu, free_rethook_node_rcu); > } > @@ -148,7 +154,6 @@ NOKPROBE_SYMBOL(rethook_recycle); > struct rethook_node *rethook_try_get(struct rethook *rh) > { > rethook_handler_t handler = READ_ONCE(rh->handler); > - struct freelist_node *fn; > > lockdep_assert_preemption_disabled(); > > @@ -165,11 +170,7 @@ struct rethook_node *rethook_try_get(struct rethook *rh) > if (unlikely(!rcu_is_watching())) > return NULL; > > - fn = freelist_try_get(&rh->pool); > - if (!fn) > - return NULL; > - > - return container_of(fn, struct rethook_node, freelist); > + return (struct rethook_node *)objpool_pop(&rh->pool); > } > NOKPROBE_SYMBOL(rethook_try_get); > > -- > 2.34.1 >
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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