Messages in this thread | | | From | Arnaldo Carvalho de Melo <> | Date | Tue, 5 May 2020 09:37:02 -0300 | Subject | Re: [PATCH v2 2/3] lib kallsyms: parse using io api |
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Em Fri, May 01, 2020 at 03:13:14PM -0700, Ian Rogers escreveu: > 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.
Applied and added this to the commit log:
Committer notes:
The internal/kallsyms-parse bench is run using:
[root@five ~]# perf bench internals kallsyms-parse # Running 'internals/kallsyms-parse' benchmark: Average kallsyms__parse took: 80.381 ms (+- 0.115 ms) [root@five ~]#
And this pre-existing test uses these routines to parse kallsyms and then compare with the info obtained from the matching ELF symtab:
[root@five ~]# perf test vmlinux 1: vmlinux symtab matches kallsyms : Ok [root@five ~]#
Signed-off-by: Ian Rogers <irogers@google.com> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> Signed-off-by: Ian Rogers <irogers@google.com> > --- > tools/lib/api/io.h | 3 ++ > tools/lib/symbol/kallsyms.c | 86 ++++++++++++++++--------------------- > 2 files changed, 41 insertions(+), 48 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..e335ac2b9e19 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) > { > @@ -15,74 +17,62 @@ bool kallsyms__is_function(char symbol_type) > return symbol_type == 'T' || symbol_type == 'W'; > } > > -/* > - * While we find nice hex chars, build a long_val. > - * Return number of chars processed. > - */ > -int hex2u64(const char *ptr, u64 *long_val) > +static void read_to_eol(struct io *io) > { > - char *p; > + int ch; > > - *long_val = strtoull(ptr, &p, 16); > - > - return p - ptr; > + 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"); > - > - if (file == NULL) > - goto out_failure; > - > - err = 0; > + struct io io; > + char bf[BUFSIZ]; > + int err; > > - while (!feof(file)) { > - u64 start; > - int line_len, len; > - char symbol_type; > - char *symbol_name; > + io.fd = open(filename, O_RDONLY, 0); > > - 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 >
--
- Arnaldo
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