linux/tools/perf/tests/maps.c
Ian Rogers 659ad3492b perf maps: Switch from rbtree to lazily sorted array for addresses
Maps is a collection of maps primarily sorted by the starting address
of the map. Prior to this change the maps were held in an rbtree
requiring 4 pointers per node. Prior to reference count checking, the
rbnode was embedded in the map so 3 pointers per node were
necessary. This change switches the rbtree to an array lazily sorted
by address, much as the array sorting nodes by name. 1 pointer is
needed per node, but to avoid excessive resizing the backing array may
be twice the number of used elements. Meaning the memory overhead is
roughly half that of the rbtree. For a perf record with
"--no-bpf-event -g -a" of true, the memory overhead of perf inject is
reduce fom 3.3MB to 3MB, so 10% or 300KB is saved.

Map inserts always happen at the end of the array. The code tracks
whether the insertion violates the sorting property. O(log n) rb-tree
complexity is switched to O(1).

Remove slides the array, so O(log n) rb-tree complexity is degraded to
O(n).

A find may need to sort the array using qsort which is O(n*log n), but
in general the maps should be sorted and so average performance should
be O(log n) as with the rbtree.

An rbtree node consumes a cache line, but with the array 4 nodes fit
on a cache line. Iteration is simplified to scanning an array rather
than pointer chasing.

Overall it is expected the performance after the change should be
comparable to before, but with half of the memory consumed.

To avoid a list and repeated logic around splitting maps,
maps__merge_in is rewritten in terms of
maps__fixup_overlap_and_insert. maps_merge_in splits the given mapping
inserting remaining gaps. maps__fixup_overlap_and_insert splits the
existing mappings, then adds the incoming mapping. By adding the new
mapping first, then re-inserting the existing mappings the splitting
behavior matches.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: James Clark <james.clark@arm.com>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Colin Ian King <colin.i.king@gmail.com>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Artem Savkov <asavkov@redhat.com>
Cc: bpf@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240210031746.4057262-2-irogers@google.com
2024-02-12 12:35:14 -08:00

166 lines
4.2 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <inttypes.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include "tests.h"
#include "map.h"
#include "maps.h"
#include "dso.h"
#include "debug.h"
struct map_def {
const char *name;
u64 start;
u64 end;
};
struct check_maps_cb_args {
struct map_def *merged;
unsigned int i;
};
static int check_maps_cb(struct map *map, void *data)
{
struct check_maps_cb_args *args = data;
struct map_def *merged = &args->merged[args->i];
if (map__start(map) != merged->start ||
map__end(map) != merged->end ||
strcmp(map__dso(map)->name, merged->name) ||
refcount_read(map__refcnt(map)) != 1) {
return 1;
}
args->i++;
return 0;
}
static int failed_cb(struct map *map, void *data __maybe_unused)
{
pr_debug("\tstart: %" PRIu64 " end: %" PRIu64 " name: '%s' refcnt: %d\n",
map__start(map),
map__end(map),
map__dso(map)->name,
refcount_read(map__refcnt(map)));
return 0;
}
static int check_maps(struct map_def *merged, unsigned int size, struct maps *maps)
{
bool failed = false;
if (maps__nr_maps(maps) != size) {
pr_debug("Expected %d maps, got %d", size, maps__nr_maps(maps));
failed = true;
} else {
struct check_maps_cb_args args = {
.merged = merged,
.i = 0,
};
failed = maps__for_each_map(maps, check_maps_cb, &args);
}
if (failed) {
pr_debug("Expected:\n");
for (unsigned int i = 0; i < size; i++) {
pr_debug("\tstart: %" PRIu64 " end: %" PRIu64 " name: '%s' refcnt: 1\n",
merged[i].start, merged[i].end, merged[i].name);
}
pr_debug("Got:\n");
maps__for_each_map(maps, failed_cb, NULL);
}
return failed ? TEST_FAIL : TEST_OK;
}
static int test__maps__merge_in(struct test_suite *t __maybe_unused, int subtest __maybe_unused)
{
unsigned int i;
struct map_def bpf_progs[] = {
{ "bpf_prog_1", 200, 300 },
{ "bpf_prog_2", 500, 600 },
{ "bpf_prog_3", 800, 900 },
};
struct map_def merged12[] = {
{ "kcore1", 100, 200 },
{ "bpf_prog_1", 200, 300 },
{ "kcore1", 300, 500 },
{ "bpf_prog_2", 500, 600 },
{ "kcore1", 600, 800 },
{ "bpf_prog_3", 800, 900 },
{ "kcore1", 900, 1000 },
};
struct map_def merged3[] = {
{ "kcore1", 100, 200 },
{ "bpf_prog_1", 200, 300 },
{ "kcore1", 300, 500 },
{ "bpf_prog_2", 500, 600 },
{ "kcore1", 600, 800 },
{ "bpf_prog_3", 800, 900 },
{ "kcore1", 900, 1000 },
{ "kcore3", 1000, 1100 },
};
struct map *map_kcore1, *map_kcore2, *map_kcore3;
int ret;
struct maps *maps = maps__new(NULL);
TEST_ASSERT_VAL("failed to create maps", maps);
for (i = 0; i < ARRAY_SIZE(bpf_progs); i++) {
struct map *map;
map = dso__new_map(bpf_progs[i].name);
TEST_ASSERT_VAL("failed to create map", map);
map__set_start(map, bpf_progs[i].start);
map__set_end(map, bpf_progs[i].end);
TEST_ASSERT_VAL("failed to insert map", maps__insert(maps, map) == 0);
map__put(map);
}
map_kcore1 = dso__new_map("kcore1");
TEST_ASSERT_VAL("failed to create map", map_kcore1);
map_kcore2 = dso__new_map("kcore2");
TEST_ASSERT_VAL("failed to create map", map_kcore2);
map_kcore3 = dso__new_map("kcore3");
TEST_ASSERT_VAL("failed to create map", map_kcore3);
/* kcore1 map overlaps over all bpf maps */
map__set_start(map_kcore1, 100);
map__set_end(map_kcore1, 1000);
/* kcore2 map hides behind bpf_prog_2 */
map__set_start(map_kcore2, 550);
map__set_end(map_kcore2, 570);
/* kcore3 map hides behind bpf_prog_3, kcore1 and adds new map */
map__set_start(map_kcore3, 880);
map__set_end(map_kcore3, 1100);
ret = maps__merge_in(maps, map_kcore1);
TEST_ASSERT_VAL("failed to merge map", !ret);
ret = check_maps(merged12, ARRAY_SIZE(merged12), maps);
TEST_ASSERT_VAL("merge check failed", !ret);
ret = maps__merge_in(maps, map_kcore2);
TEST_ASSERT_VAL("failed to merge map", !ret);
ret = check_maps(merged12, ARRAY_SIZE(merged12), maps);
TEST_ASSERT_VAL("merge check failed", !ret);
ret = maps__merge_in(maps, map_kcore3);
TEST_ASSERT_VAL("failed to merge map", !ret);
ret = check_maps(merged3, ARRAY_SIZE(merged3), maps);
TEST_ASSERT_VAL("merge check failed", !ret);
maps__zput(maps);
map__zput(map_kcore1);
map__zput(map_kcore2);
map__zput(map_kcore3);
return TEST_OK;
}
DEFINE_SUITE("maps__merge_in", maps__merge_in);