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[98.38.17.99]) by smtp.googlemail.com with ESMTPSA id 586e51a60fabf-4881f4d7861sm4146915fac.1.2026.09.19.20.59.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 20:59:02 -0700 (PDT) From: Jim Cromie Date: Sat, 19 Sep 2026 21:58:55 -0600 Subject: [PATCH 1/3] kallsyms: Add test_kallsyms_perf module to benchmark lookup latency Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260919-ksyms-tune-v1-1-d85c97da1a32@gmail.com> References: <20260919-ksyms-tune-v1-0-d85c97da1a32@gmail.com> In-Reply-To: <20260919-ksyms-tune-v1-0-d85c97da1a32@gmail.com> To: Andrew Morton Cc: Lorenzo Stoakes , Kees Cook , Masahiro Yamada , linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, bpf@vger.kernel.org, Jim Cromie X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1789876740; l=9420; i=jim.cromie@gmail.com; s=20260203; h=from:subject:message-id; bh=nSVguYsya202ycWnyh7LvZPegeG4xaW8+imMMxZ/vE0=; b=a7B9miUPH8gTO/u2Uk31hK0exxzWkLBwVe5iAlQATS4u4hLAGfj1phiyt7a60rP7m6PxAYp+R GLR8d9sBTB+ANEnD36U56DdWK3Ujl/PicYimkjnIEGlfpuf5uQhievV X-Developer-Key: i=jim.cromie@gmail.com; a=ed25519; pk=C6E5ODlPQo7ZBynATXH9wg7K6HxP0pIXyf4s38Qw0XE= To evaluate optimizations and measure performance regressions across kallsyms lookups, add a lightweight microbenchmark module in lib/. The module exercises the primary kallsyms resolution paths: 0. Name-to-Address binary search: Benchmarks lookups across common kernel functions (hits) and non-existent symbol strings (misses, exercising the full binary search tree depth). 1. Address-to-Name resolution: Benchmarks address decoding latency via sprint_symbol() and sprint_symbol_no_offset(). 2. Sequential table scan: Measures complete table iteration latency via kallsyms_on_each_symbol(). The module exposes a num_iters parameter (default: 100,000) and a sysfs trigger to repeat benchmark runs on demand. Signed-off-by: Jim Cromie --- kernel/kallsyms.c | 2 + lib/Kconfig.debug | 10 +++ lib/Makefile | 1 + lib/test_kallsyms_perf.c | 228 +++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 241 insertions(+) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index aec2f06858af..b9e573e9a10b 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -261,6 +261,7 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, unsigned long), } return 0; } +EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol); int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long), const char *name, void *data) @@ -279,6 +280,7 @@ int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long), return ret; } +EXPORT_SYMBOL_GPL(kallsyms_on_each_match_symbol); static unsigned long get_symbol_pos(unsigned long addr, unsigned long *symbolsize, diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 134b15a44625..2a8b1aaee23b 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -3122,6 +3122,16 @@ config TEST_STATIC_KEYS If unsure, say N. +config TEST_KALLSYMS_PERF + tristate "kallsyms performance benchmark test module" + default m + help + This builds the test_kallsyms_perf module to benchmark latency + across Name-to-Address binary search, Address-to-Name resolution, + and full table walks. + + If unsure, say N. + config TEST_DYNAMIC_DEBUG tristate "Test DYNAMIC_DEBUG" depends on DYNAMIC_DEBUG diff --git a/lib/Makefile b/lib/Makefile index dfab958327c5..149968ff3f6b 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -85,6 +85,7 @@ obj-$(CONFIG_TEST_RHASHTABLE) += test_rhashtable.o obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o obj-$(CONFIG_TEST_DYNAMIC_DEBUG) += test_dynamic_debug.o +obj-$(CONFIG_TEST_KALLSYMS_PERF) += test_kallsyms_perf.o obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_KASAN),yy) diff --git a/lib/test_kallsyms_perf.c b/lib/test_kallsyms_perf.c new file mode 100644 index 000000000000..c649e55dae3b --- /dev/null +++ b/lib/test_kallsyms_perf.c @@ -0,0 +1,228 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Microbenchmark and correctness test module for kallsyms subsystem + * + * Measures CPU latency across: + * - Name-to-Address binary search (hits & misses) + * - Address-to-Name symbol resolution (sprint_symbol, buildid) + * - Full kernel symbol iteration (kallsyms_on_each_symbol) + */ + +#define pr_fmt(fmt) "test_kallsyms: " fmt + +#include +#include +#include +#include +#include +#include + +static unsigned int num_iters = 100000; +module_param(num_iters, uint, 0644); +MODULE_PARM_DESC(num_iters, "Number of iterations per microbenchmark"); + +static const char * const hit_symbols[] = { + "_printk", + "schedule", + "vfs_read", + "do_sys_openat2", + "kernel_clone", + "tcp_v4_rcv", + "kallsyms_lookup_names", + "vm_area_alloc", +}; + +static const char * const miss_symbols[] = { + "nonexistent_symbol_0001", + "xyz_dummy_missing_symbol", + "__never_compiled_in_kernel", + "ext4_nonexistent_func_xyz", + "bpf_not_real_helper_stub", + "vfs_missing_handler_probe", + "tcp_v4_unimplemented_path", + "driver_fake_init_routine", +}; + +static int match_cb(void *data, unsigned long addr) +{ + unsigned long *out = data; + + *out = addr; + return 1; +} + +static int count_cb(void *data, const char *name, unsigned long addr) +{ + unsigned long *cnt = data; + + (*cnt)++; + return 0; +} + +static void run_name_lookup_bench(void) +{ + u64 t0, t1, dt_hit, dt_miss; + unsigned long addr = 0; + unsigned int i, nr_hits, nr_misses; + + nr_hits = ARRAY_SIZE(hit_symbols); + nr_misses = ARRAY_SIZE(miss_symbols); + + /* 0. Correctness validation */ + for (i = 0; i < nr_hits; i++) { + const char *sym = hit_symbols[i]; + unsigned long a1 = 0; + + kallsyms_on_each_match_symbol(match_cb, sym, &a1); + if (!a1) + pr_err("CORRECTNESS FAILURE: hit sym '%s' not found\n", sym); + } + for (i = 0; i < nr_misses; i++) { + const char *sym = miss_symbols[i]; + unsigned long a1 = 0; + + kallsyms_on_each_match_symbol(match_cb, sym, &a1); + if (a1) + pr_err("CORRECTNESS FAILURE: miss sym '%s' unexpectedly found a1=%lx\n", + sym, a1); + } + + /* 1. Name search: Existing symbols (Hits) */ + t0 = ktime_get_ns(); + for (i = 0; i < num_iters; i++) { + const char *sym = hit_symbols[i % nr_hits]; + + kallsyms_on_each_match_symbol(match_cb, sym, &addr); + OPTIMIZER_HIDE_VAR(addr); + } + t1 = ktime_get_ns(); + dt_hit = t1 - t0; + + /* 2. Name search: Non-existent symbols (Misses - 17 bsearch probes) */ + t0 = ktime_get_ns(); + for (i = 0; i < num_iters; i++) { + const char *sym = miss_symbols[i % nr_misses]; + + kallsyms_on_each_match_symbol(match_cb, sym, &addr); + OPTIMIZER_HIDE_VAR(addr); + } + t1 = ktime_get_ns(); + dt_miss = t1 - t0; + + pr_info("Name Search Hit: %llu ns/lookup (%llu ms total, %u iters)\n", + dt_hit / num_iters, dt_hit / 1000000, num_iters); + pr_info("Name Search Miss: %llu ns/lookup (%llu ms total, %u iters)\n", + dt_miss / num_iters, dt_miss / 1000000, num_iters); +} + +static void run_address_lookup_bench(void) +{ + u64 t0, t1, dt_sprint, dt_bldid; + char symname[KSYM_SYMBOL_LEN]; + unsigned long addrs[ARRAY_SIZE(hit_symbols)]; + unsigned int i, nr_addrs = 0; + + for (i = 0; i < ARRAY_SIZE(hit_symbols); i++) { + unsigned long addr = 0; + + kallsyms_on_each_match_symbol(match_cb, hit_symbols[i], &addr); + if (addr) + addrs[nr_addrs++] = addr; + } + + if (!nr_addrs) { + pr_warn("Address benchmark skipped: no test addresses resolved\n"); + return; + } + + /* 1. Address-to-name resolution (sprint_symbol) */ + t0 = ktime_get_ns(); + for (i = 0; i < num_iters; i++) { + unsigned long addr = addrs[i % nr_addrs]; + + sprint_symbol(symname, addr); + barrier_data(symname); + } + t1 = ktime_get_ns(); + dt_sprint = t1 - t0; + + /* 2. Address without offset (sprint_symbol_no_offset) */ + t0 = ktime_get_ns(); + for (i = 0; i < num_iters; i++) { + unsigned long addr = addrs[i % nr_addrs]; + + sprint_symbol_no_offset(symname, addr); + barrier_data(symname); + } + t1 = ktime_get_ns(); + dt_bldid = t1 - t0; + + pr_info("sprint_symbol: %llu ns/lookup (%llu ms total, %u iters)\n", + dt_sprint / num_iters, dt_sprint / 1000000, num_iters); + pr_info("sprint_symbol_no_offset: %llu ns/lookup (%llu ms total, %u iters)\n", + dt_bldid / num_iters, dt_bldid / 1000000, num_iters); +} + +static void run_table_walk_bench(void) +{ + u64 t0, t1, dt_walk; + unsigned long total_symbols = 0; + int iter = 50; + int i; + + t0 = ktime_get_ns(); + for (i = 0; i < iter; i++) { + total_symbols = 0; + kallsyms_on_each_symbol(count_cb, &total_symbols); + } + t1 = ktime_get_ns(); + dt_walk = t1 - t0; + + pr_info("Table Full Walk: %llu us/pass (%lu symbols scanned, %d passes)\n", + (dt_walk / iter) / 1000, total_symbols, iter); +} + +static int run_kallsyms_benchmark(void) +{ + pr_info("==================================================\n"); + pr_info("Starting kallsyms performance benchmark (iters=%u)\n", num_iters); + pr_info("==================================================\n"); + + run_name_lookup_bench(); + run_address_lookup_bench(); + run_table_walk_bench(); + + pr_info("==================================================\n"); + pr_info("kallsyms benchmark complete\n"); + pr_info("==================================================\n"); + + return 0; +} + +static int param_set_trigger(const char *val, const struct kernel_param *kp) +{ + return run_kallsyms_benchmark(); +} + +static const struct kernel_param_ops param_ops_trigger = { + .set = param_set_trigger, +}; +module_param_cb(run_test, ¶m_ops_trigger, NULL, 0200); +MODULE_PARM_DESC(run_test, "Write 1 to trigger kallsyms benchmark run"); + +static int __init test_kallsyms_init(void) +{ + return run_kallsyms_benchmark(); +} + +static void __exit test_kallsyms_exit(void) +{ + pr_info("test_kallsyms module unloaded\n"); +} + +module_init(test_kallsyms_init); +module_exit(test_kallsyms_exit); + +MODULE_DESCRIPTION("Microbenchmark test module for kallsyms subsystem"); +MODULE_AUTHOR("Jim Cromie "); +MODULE_LICENSE("GPL"); -- 2.55.0