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53df2b9344
'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.
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 ~]#
Also we can't remove hex2u64() in this patch as this breaks the build:
/usr/bin/ld: /tmp/build/perf/perf-in.o: in function `modules__parse':
/home/acme/git/perf/tools/perf/util/symbol.c:607: undefined reference to `hex2u64'
/usr/bin/ld: /home/acme/git/perf/tools/perf/util/symbol.c:607: undefined reference to `hex2u64'
/usr/bin/ld: /tmp/build/perf/perf-in.o: in function `dso__load_perf_map':
/home/acme/git/perf/tools/perf/util/symbol.c:1477: undefined reference to `hex2u64'
/usr/bin/ld: /home/acme/git/perf/tools/perf/util/symbol.c:1483: undefined reference to `hex2u64'
collect2: error: ld returned 1 exit status
Leave it there, move it in the next patch.
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lore.kernel.org/lkml/20200501221315.54715-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
116 lines
2.5 KiB
C
116 lines
2.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Lightweight buffered reading library.
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*
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* Copyright 2019 Google LLC.
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*/
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#ifndef __API_IO__
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#define __API_IO__
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#include <stdlib.h>
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#include <unistd.h>
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struct io {
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/* File descriptor being read/ */
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int fd;
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/* Size of the read buffer. */
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unsigned int buf_len;
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/* Pointer to storage for buffering read. */
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char *buf;
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/* End of the storage. */
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char *end;
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/* Currently accessed data pointer. */
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char *data;
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/* Set true on when the end of file on read error. */
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bool eof;
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};
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static inline void io__init(struct io *io, int fd,
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char *buf, unsigned int buf_len)
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{
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io->fd = fd;
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io->buf_len = buf_len;
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io->buf = buf;
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io->end = buf;
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io->data = buf;
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io->eof = false;
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}
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/* Reads one character from the "io" file with similar semantics to fgetc. */
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static inline int io__get_char(struct io *io)
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{
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char *ptr = io->data;
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if (io->eof)
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return -1;
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if (ptr == io->end) {
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ssize_t n = read(io->fd, io->buf, io->buf_len);
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if (n <= 0) {
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io->eof = true;
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return -1;
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}
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ptr = &io->buf[0];
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io->end = &io->buf[n];
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}
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io->data = ptr + 1;
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return *ptr;
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}
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/* Read a hexadecimal value with no 0x prefix into the out argument hex. If the
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* first character isn't hexadecimal returns -2, io->eof returns -1, otherwise
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* returns the character after the hexadecimal value which may be -1 for eof.
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* If the read value is larger than a u64 the high-order bits will be dropped.
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*/
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static inline int io__get_hex(struct io *io, __u64 *hex)
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{
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bool first_read = true;
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*hex = 0;
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while (true) {
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int ch = io__get_char(io);
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if (ch < 0)
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return ch;
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if (ch >= '0' && ch <= '9')
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*hex = (*hex << 4) | (ch - '0');
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else if (ch >= 'a' && ch <= 'f')
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*hex = (*hex << 4) | (ch - 'a' + 10);
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else if (ch >= 'A' && ch <= 'F')
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*hex = (*hex << 4) | (ch - 'A' + 10);
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else if (first_read)
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return -2;
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else
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return ch;
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first_read = false;
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}
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}
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/* Read a positive decimal value with out argument dec. If the first character
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* isn't a decimal returns -2, io->eof returns -1, otherwise returns the
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* character after the decimal value which may be -1 for eof. If the read value
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* is larger than a u64 the high-order bits will be dropped.
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*/
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static inline int io__get_dec(struct io *io, __u64 *dec)
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{
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bool first_read = true;
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*dec = 0;
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while (true) {
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int ch = io__get_char(io);
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if (ch < 0)
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return ch;
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if (ch >= '0' && ch <= '9')
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*dec = (*dec * 10) + ch - '0';
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else if (first_read)
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return -2;
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else
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return ch;
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first_read = false;
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}
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}
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#endif /* __API_IO__ */
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