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author | wuqiang.matt <wuqiang.matt@bytedance.com> | 2023-10-17 21:56:52 +0800 |
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committer | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2023-10-18 23:59:54 +0900 |
commit | 4bbd9345565933823f38a419df65661f12adbe5e (patch) | |
tree | debaf6ea237ce00ce92be26ce3ef8d6999cbd24e /kernel/trace | |
parent | 92f90d3b0d5e384f218c8068138ed1b3afa025af (diff) | |
download | lwn-4bbd9345565933823f38a419df65661f12adbe5e.tar.gz lwn-4bbd9345565933823f38a419df65661f12adbe5e.zip |
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 <wuqiang.matt@bytedance.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r-- | kernel/trace/fprobe.c | 28 | ||||
-rw-r--r-- | kernel/trace/rethook.c | 90 |
2 files changed, 50 insertions, 68 deletions
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 3b21f4063258..6890f4fd17fc 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -187,7 +187,7 @@ 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) return -EINVAL; @@ -205,26 +205,18 @@ static int fprobe_init_rethook(struct fprobe *fp, int num) if (size < 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) + fp->entry_data_size, 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), size); + 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; @@ -379,14 +371,14 @@ int unregister_fprobe(struct fprobe *fp) if (!fprobe_is_registered(fp)) return -EINVAL; - if (fp->rethook) + if (!IS_ERR_OR_NULL(fp->rethook)) rethook_stop(fp->rethook); ret = unregister_ftrace_function(&fp->ops); if (ret < 0) return ret; - if (fp->rethook) + if (!IS_ERR_OR_NULL(fp->rethook)) rethook_free(fp->rethook); ftrace_free_filter(&fp->ops); diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c index 5eb9b598f4e9..13c8e6773892 100644 --- a/kernel/trace/rethook.c +++ b/kernel/trace/rethook.c @@ -9,6 +9,7 @@ #include <linux/rethook.h> #include <linux/slab.h> #include <linux/sort.h> +#include <linux/smp.h> /* Return hook list (shadow stack by list) */ @@ -36,21 +37,7 @@ 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++; - } - - /* The rh->ref is the number of pooled node + 1 */ - if (refcount_sub_and_test(count, &rh->ref)) - kfree(rh); + objpool_fini(&rh->pool); } /** @@ -83,54 +70,62 @@ 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 + * @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); + } 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); + objpool_drop(node, &rh->pool); } /** @@ -145,7 +140,7 @@ 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); } @@ -161,7 +156,6 @@ 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(); @@ -178,11 +172,7 @@ 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); |