Commit 910a742d authored by Michel Lespinasse's avatar Michel Lespinasse Committed by Linus Torvalds
Browse files

rbtree: performance and correctness test 



This small module helps measure the performance of rbtree insert and
erase.

Additionally, we run a few correctness tests to check that the rbtrees
have all desired properties:

- contains the right number of nodes in the order desired,
- never two consecutive red nodes on any path,
- all paths to leaf nodes have the same number of black nodes,
- root node is black

[akpm@linux-foundation.org: fix printk warning: sparc64 cycles_t is unsigned long]
Signed-off-by: default avatarMichel Lespinasse <walken@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Daniel Santos <daniel.santos@pobox.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bf7ad8ee

lib/Kconfig.debug

+7 −0
Original line number Diff line number Diff line
@@ -1282,6 +1282,13 @@ config LATENCYTOP 
source mm/Kconfig.debug

source kernel/trace/Kconfig



config RBTREE_TEST

	tristate "Red-Black tree test"

	depends on m && DEBUG_KERNEL

	help

	  A benchmark measuring the performance of the rbtree library.

	  Also includes rbtree invariant checks.



config PROVIDE_OHCI1394_DMA_INIT

	bool "Remote debugging over FireWire early on boot"

	depends on PCI && X86

lib/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -140,6 +140,8 @@ $(foreach file, $(libfdt_files), \ 
	$(eval CFLAGS_$(file) = -I$(src)/../scripts/dtc/libfdt))

lib-$(CONFIG_LIBFDT) += $(libfdt_files)



obj-$(CONFIG_RBTREE_TEST) += rbtree_test.o



hostprogs-y	:= gen_crc32table

clean-files	:= crc32table.h

lib/rbtree_test.c

0 → 100644
+135 −0
Original line number Diff line number Diff line 
#include <linux/module.h>

#include <linux/rbtree.h>

#include <linux/random.h>

#include <asm/timex.h>



#define NODES       100

#define PERF_LOOPS  100000

#define CHECK_LOOPS 100



struct test_node {

	struct rb_node rb;

	u32 key;

};



static struct rb_root root = RB_ROOT;

static struct test_node nodes[NODES];



static struct rnd_state rnd;



static void insert(struct test_node *node, struct rb_root *root)

{

	struct rb_node **new = &root->rb_node, *parent = NULL;



	while (*new) {

		parent = *new;

		if (node->key < rb_entry(parent, struct test_node, rb)->key)

			new = &parent->rb_left;

		else

			new = &parent->rb_right;

	}



	rb_link_node(&node->rb, parent, new);

	rb_insert_color(&node->rb, root);

}



static inline void erase(struct test_node *node, struct rb_root *root)

{

	rb_erase(&node->rb, root);

}



static void init(void)

{

	int i;

	for (i = 0; i < NODES; i++)

		nodes[i].key = prandom32(&rnd);

}



static bool is_red(struct rb_node *rb)

{

	return !(rb->__rb_parent_color & 1);

}



static int black_path_count(struct rb_node *rb)

{

	int count;

	for (count = 0; rb; rb = rb_parent(rb))

		count += !is_red(rb);

	return count;

}



static void check(int nr_nodes)

{

	struct rb_node *rb;

	int count = 0;

	int blacks;

	u32 prev_key = 0;



	for (rb = rb_first(&root); rb; rb = rb_next(rb)) {

		struct test_node *node = rb_entry(rb, struct test_node, rb);

		WARN_ON_ONCE(node->key < prev_key);

		WARN_ON_ONCE(is_red(rb) &&

			     (!rb_parent(rb) || is_red(rb_parent(rb))));

		if (!count)

			blacks = black_path_count(rb);

		else

			WARN_ON_ONCE((!rb->rb_left || !rb->rb_right) &&

				     blacks != black_path_count(rb));

		prev_key = node->key;

		count++;

	}

	WARN_ON_ONCE(count != nr_nodes);

}



static int rbtree_test_init(void)

{

	int i, j;

	cycles_t time1, time2, time;



	printk(KERN_ALERT "rbtree testing");



	prandom32_seed(&rnd, 3141592653589793238);

	init();



	time1 = get_cycles();



	for (i = 0; i < PERF_LOOPS; i++) {

		for (j = 0; j < NODES; j++)

			insert(nodes + j, &root);

		for (j = 0; j < NODES; j++)

			erase(nodes + j, &root);

	}



	time2 = get_cycles();

	time = time2 - time1;



	time = div_u64(time, PERF_LOOPS);

	printk(" -> %llu cycles\n", (unsigned long long)time);



	for (i = 0; i < CHECK_LOOPS; i++) {

		init();

		for (j = 0; j < NODES; j++) {

			check(j);

			insert(nodes + j, &root);

		}

		for (j = 0; j < NODES; j++) {

			check(NODES - j);

			erase(nodes + j, &root);

		}

		check(0);

	}



	return -EAGAIN; /* Fail will directly unload the module */

}



static void rbtree_test_exit(void)

{

	printk(KERN_ALERT "test exit\n");

}



module_init(rbtree_test_init)

module_exit(rbtree_test_exit)



MODULE_LICENSE("GPL");

MODULE_AUTHOR("Michel Lespinasse");

MODULE_DESCRIPTION("Red Black Tree test");

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