From: Namhyung Kim Date: Tue, 1 Apr 2025 06:30:55 +0000 (-0700) Subject: perf lock contention: Symbolize zone->lock using BTF X-Git-Tag: v6.16-rc1~57^2~122 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=13f35928a4e6fe158f358c3d2f16c2319f1ace53;p=thirdparty%2Flinux.git perf lock contention: Symbolize zone->lock using BTF The struct zone is embedded in struct pglist_data which can be allocated for each NUMA node early in the boot process. As it's not a slab object nor a global lock, this was not symbolized. Since the zone->lock is often contended, it'd be nice if we can symbolize it. On NUMA systems, node_data array will have pointers for struct pglist_data. By following the pointer, it can calculate the address of each zone and its lock using BTF. On UMA, it can just use contig_page_data and its zones. The following example shows the zone lock contention at the end. $ sudo ./perf lock con -abl -E 5 -- ./perf bench sched messaging # Running 'sched/messaging' benchmark: # 20 sender and receiver processes per group # 10 groups == 400 processes run Total time: 0.038 [sec] contended total wait max wait avg wait address symbol 5167 18.17 ms 10.27 us 3.52 us ffff953340052d00 &kmem_cache_node (spinlock) 38 11.75 ms 465.49 us 309.13 us ffff95334060c480 &sock_inode_cache (spinlock) 3916 10.13 ms 10.43 us 2.59 us ffff953342aecb40 &kmem_cache_node (spinlock) 2963 10.02 ms 13.75 us 3.38 us ffff9533d2344098 &kmalloc-rnd-08-2k (spinlock) 216 5.05 ms 99.49 us 23.39 us ffff9542bf7d65d0 zone_lock (spinlock) Signed-off-by: Namhyung Kim Tested-by: Arnaldo Carvalho de Melo Cc: Adrian Hunter Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Kan Liang Cc: Peter Zijlstra Cc: Song Liu Cc: Stephane Eranian Cc: bpf@vger.kernel.org Cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/20250401063055.7431-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c index 5af8f6d1bc952..98395667220e5 100644 --- a/tools/perf/util/bpf_lock_contention.c +++ b/tools/perf/util/bpf_lock_contention.c @@ -12,6 +12,7 @@ #include "util/lock-contention.h" #include #include +#include #include #include #include @@ -35,28 +36,26 @@ static bool slab_cache_equal(long key1, long key2, void *ctx __maybe_unused) static void check_slab_cache_iter(struct lock_contention *con) { - struct btf *btf = btf__load_vmlinux_btf(); s32 ret; hashmap__init(&slab_hash, slab_cache_hash, slab_cache_equal, /*ctx=*/NULL); - if (btf == NULL) { + con->btf = btf__load_vmlinux_btf(); + if (con->btf == NULL) { pr_debug("BTF loading failed: %s\n", strerror(errno)); return; } - ret = btf__find_by_name_kind(btf, "bpf_iter__kmem_cache", BTF_KIND_STRUCT); + ret = btf__find_by_name_kind(con->btf, "bpf_iter__kmem_cache", BTF_KIND_STRUCT); if (ret < 0) { bpf_program__set_autoload(skel->progs.slab_cache_iter, false); pr_debug("slab cache iterator is not available: %d\n", ret); - goto out; + return; } has_slab_iter = true; bpf_map__set_max_entries(skel->maps.slab_caches, con->map_nr_entries); -out: - btf__free(btf); } static void run_slab_cache_iter(void) @@ -109,6 +108,75 @@ static void exit_slab_cache_iter(void) hashmap__clear(&slab_hash); } +static void init_numa_data(struct lock_contention *con) +{ + struct symbol *sym; + struct map *kmap; + char *buf = NULL, *p; + size_t len; + long last = -1; + int ret; + + /* + * 'struct zone' is embedded in 'struct pglist_data' as an array. + * As we may not have full information of the struct zone in the + * (fake) vmlinux.h, let's get the actual size from BTF. + */ + ret = btf__find_by_name_kind(con->btf, "zone", BTF_KIND_STRUCT); + if (ret < 0) { + pr_debug("cannot get type of struct zone: %d\n", ret); + return; + } + + ret = btf__resolve_size(con->btf, ret); + if (ret < 0) { + pr_debug("cannot get size of struct zone: %d\n", ret); + return; + } + skel->rodata->sizeof_zone = ret; + + /* UMA system doesn't have 'node_data[]' - just use contig_page_data. */ + sym = machine__find_kernel_symbol_by_name(con->machine, + "contig_page_data", + &kmap); + if (sym) { + skel->rodata->contig_page_data_addr = map__unmap_ip(kmap, sym->start); + map__put(kmap); + return; + } + + /* + * The 'node_data' is an array of pointers to struct pglist_data. + * It needs to follow the pointer for each node in BPF to get the + * address of struct pglist_data and its zones. + */ + sym = machine__find_kernel_symbol_by_name(con->machine, + "node_data", + &kmap); + if (sym == NULL) + return; + + skel->rodata->node_data_addr = map__unmap_ip(kmap, sym->start); + map__put(kmap); + + /* get the number of online nodes using the last node number + 1 */ + ret = sysfs__read_str("devices/system/node/online", &buf, &len); + if (ret < 0) { + pr_debug("failed to read online node: %d\n", ret); + return; + } + + p = buf; + while (p && *p) { + last = strtol(p, &p, 0); + + if (p && (*p == ',' || *p == '-' || *p == '\n')) + p++; + } + skel->rodata->nr_nodes = last + 1; + free(buf); +} + int lock_contention_prepare(struct lock_contention *con) { int i, fd; @@ -218,6 +286,8 @@ int lock_contention_prepare(struct lock_contention *con) bpf_map__set_max_entries(skel->maps.slab_filter, nslabs); + init_numa_data(con); + if (lock_contention_bpf__load(skel) < 0) { pr_err("Failed to load lock-contention BPF skeleton\n"); return -1; @@ -505,6 +575,11 @@ static const char *lock_contention_get_name(struct lock_contention *con, return "rq_lock"; } + if (!bpf_map_lookup_elem(lock_fd, &key->lock_addr_or_cgroup, &flags)) { + if (flags == LOCK_CLASS_ZONE_LOCK) + return "zone_lock"; + } + /* look slab_hash for dynamic locks in a slab object */ if (hashmap__find(&slab_hash, flags & LCB_F_SLAB_ID_MASK, &slab_data)) { snprintf(name_buf, sizeof(name_buf), "&%s", slab_data->name); @@ -743,6 +818,7 @@ int lock_contention_finish(struct lock_contention *con) } exit_slab_cache_iter(); + btf__free(con->btf); return 0; } diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c index 69be7a4234e07..6f12c7d978a2e 100644 --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c @@ -11,6 +11,9 @@ /* for collect_lock_syms(). 4096 was rejected by the verifier */ #define MAX_CPUS 1024 +/* for collect_zone_lock(). It should be more than the actual zones. */ +#define MAX_ZONES 10 + /* lock contention flags from include/trace/events/lock.h */ #define LCB_F_SPIN (1U << 0) #define LCB_F_READ (1U << 1) @@ -801,6 +804,11 @@ out: extern struct rq runqueues __ksym; +const volatile __u64 contig_page_data_addr; +const volatile __u64 node_data_addr; +const volatile int nr_nodes; +const volatile int sizeof_zone; + struct rq___old { raw_spinlock_t lock; } __attribute__((preserve_access_index)); @@ -809,6 +817,59 @@ struct rq___new { raw_spinlock_t __lock; } __attribute__((preserve_access_index)); +static void collect_zone_lock(void) +{ + __u64 nr_zones, zone_off; + __u64 lock_addr, lock_off; + __u32 lock_flag = LOCK_CLASS_ZONE_LOCK; + + zone_off = offsetof(struct pglist_data, node_zones); + lock_off = offsetof(struct zone, lock); + + if (contig_page_data_addr) { + struct pglist_data *contig_page_data; + + contig_page_data = (void *)(long)contig_page_data_addr; + nr_zones = BPF_CORE_READ(contig_page_data, nr_zones); + + for (int i = 0; i < MAX_ZONES; i++) { + __u64 zone_addr; + + if (i >= nr_zones) + break; + + zone_addr = contig_page_data_addr + (sizeof_zone * i) + zone_off; + lock_addr = zone_addr + lock_off; + + bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY); + } + } else if (nr_nodes > 0) { + struct pglist_data **node_data = (void *)(long)node_data_addr; + + for (int i = 0; i < nr_nodes; i++) { + struct pglist_data *pgdat = NULL; + int err; + + err = bpf_core_read(&pgdat, sizeof(pgdat), &node_data[i]); + if (err < 0 || pgdat == NULL) + break; + + nr_zones = BPF_CORE_READ(pgdat, nr_zones); + for (int k = 0; k < MAX_ZONES; k++) { + __u64 zone_addr; + + if (k >= nr_zones) + break; + + zone_addr = (__u64)(void *)pgdat + (sizeof_zone * k) + zone_off; + lock_addr = zone_addr + lock_off; + + bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY); + } + } + } +} + SEC("raw_tp/bpf_test_finish") int BPF_PROG(collect_lock_syms) { @@ -830,6 +891,9 @@ int BPF_PROG(collect_lock_syms) lock_flag = LOCK_CLASS_RQLOCK; bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY); } + + collect_zone_lock(); + return 0; } diff --git a/tools/perf/util/bpf_skel/lock_data.h b/tools/perf/util/bpf_skel/lock_data.h index 15f5743bd409f..28c5e5aced7fc 100644 --- a/tools/perf/util/bpf_skel/lock_data.h +++ b/tools/perf/util/bpf_skel/lock_data.h @@ -67,6 +67,7 @@ enum lock_aggr_mode { enum lock_class_sym { LOCK_CLASS_NONE, LOCK_CLASS_RQLOCK, + LOCK_CLASS_ZONE_LOCK, }; struct slab_cache_data { diff --git a/tools/perf/util/bpf_skel/vmlinux/vmlinux.h b/tools/perf/util/bpf_skel/vmlinux/vmlinux.h index 7b81d3173917f..a59ce912be18c 100644 --- a/tools/perf/util/bpf_skel/vmlinux/vmlinux.h +++ b/tools/perf/util/bpf_skel/vmlinux/vmlinux.h @@ -203,4 +203,13 @@ struct bpf_iter__kmem_cache { struct kmem_cache *s; } __attribute__((preserve_access_index)); +struct zone { + spinlock_t lock; +} __attribute__((preserve_access_index)); + +struct pglist_data { + struct zone node_zones[6]; /* value for all possible config */ + int nr_zones; +} __attribute__((preserve_access_index)); + #endif // __VMLINUX_H diff --git a/tools/perf/util/lock-contention.h b/tools/perf/util/lock-contention.h index b5d916aa49df6..d331ce8e3caad 100644 --- a/tools/perf/util/lock-contention.h +++ b/tools/perf/util/lock-contention.h @@ -142,6 +142,7 @@ struct lock_contention { struct lock_filter *filters; struct lock_contention_fails fails; struct rb_root cgroups; + void *btf; unsigned long map_nr_entries; int max_stack; int stack_skip;