Perf record will call kallsyms__parse 4 times during startup and process megabytes of data. This changes kallsyms__parse to use the io library rather than fgets to improve performance of the user code by over 8%.
Before: Running 'internals/kallsyms-parse' benchmark: Average kallsyms__parse took: 103.988 ms (+- 0.203 ms) After: Running 'internals/kallsyms-parse' benchmark: Average kallsyms__parse took: 95.571 ms (+- 0.006 ms) For a workload like: $ perf record /bin/true Run under 'perf record -e cycles:u -g' the time goes from: Before 30.10% 1.67% perf perf [.] kallsyms__parse After 25.55% 20.04% perf perf [.] kallsyms__parse So a little under 5% of the start-up time is removed. A lot of what remains is on the kernel side, but caching kallsyms within perf would at least impact memory footprint. Signed-off-by: Ian Rogers <[email protected]> --- tools/lib/api/io.h | 3 ++ tools/lib/symbol/kallsyms.c | 81 +++++++++++++++++++------------------ 2 files changed, 45 insertions(+), 39 deletions(-) diff --git a/tools/lib/api/io.h b/tools/lib/api/io.h index b7e55b5f8a4a..777c20f6b604 100644 --- a/tools/lib/api/io.h +++ b/tools/lib/api/io.h @@ -7,6 +7,9 @@ #ifndef __API_IO__ #define __API_IO__ +#include <stdlib.h> +#include <unistd.h> + struct io { /* File descriptor being read/ */ int fd; diff --git a/tools/lib/symbol/kallsyms.c b/tools/lib/symbol/kallsyms.c index 1a7a9f877095..1f2f519a4e3f 100644 --- a/tools/lib/symbol/kallsyms.c +++ b/tools/lib/symbol/kallsyms.c @@ -1,7 +1,9 @@ // SPDX-License-Identifier: GPL-2.0 #include "symbol/kallsyms.h" +#include "api/io.h" #include <stdio.h> -#include <stdlib.h> +#include <sys/stat.h> +#include <fcntl.h> u8 kallsyms2elf_type(char type) { @@ -28,61 +30,62 @@ int hex2u64(const char *ptr, u64 *long_val) return p - ptr; } +static void read_to_eol(struct io *io) +{ + int ch; + + for (;;) { + ch = io__get_char(io); + if (ch < 0 || ch == '\n') + return; + } +} + int kallsyms__parse(const char *filename, void *arg, int (*process_symbol)(void *arg, const char *name, char type, u64 start)) { - char *line = NULL; - size_t n; - int err = -1; - FILE *file = fopen(filename, "r"); + struct io io; + char bf[BUFSIZ]; + int err; - if (file == NULL) - goto out_failure; + io.fd = open(filename, O_RDONLY, 0); - err = 0; - - while (!feof(file)) { - u64 start; - int line_len, len; - char symbol_type; - char *symbol_name; - - line_len = getline(&line, &n, file); - if (line_len < 0 || !line) - break; + if (io.fd < 0) + return -1; - line[--line_len] = '\0'; /* \n */ + io__init(&io, io.fd, bf, sizeof(bf)); - len = hex2u64(line, &start); + err = 0; + while (!io.eof) { + __u64 start; + int ch; + size_t i; + char symbol_type; + char symbol_name[KSYM_NAME_LEN + 1]; - /* Skip the line if we failed to parse the address. */ - if (!len) + if (io__get_hex(&io, &start) != ' ') { + read_to_eol(&io); continue; - - len++; - if (len + 2 >= line_len) + } + symbol_type = io__get_char(&io); + if (io__get_char(&io) != ' ') { + read_to_eol(&io); continue; - - symbol_type = line[len]; - len += 2; - symbol_name = line + len; - len = line_len - len; - - if (len >= KSYM_NAME_LEN) { - err = -1; - break; } + for (i = 0; i < sizeof(symbol_name); i++) { + ch = io__get_char(&io); + if (ch < 0 || ch == '\n') + break; + symbol_name[i] = ch; + } + symbol_name[i] = '\0'; err = process_symbol(arg, symbol_name, symbol_type, start); if (err) break; } - free(line); - fclose(file); + close(io.fd); return err; - -out_failure: - return -1; } -- 2.26.2.526.g744177e7f7-goog
