diff options
author | Ian Rogers <irogers@google.com> | 2020-04-14 22:40:49 -0700 |
---|---|---|
committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2020-04-30 10:48:28 -0300 |
commit | e95770af4c4a280fab2080529d30452a7628d45d (patch) | |
tree | 6abebd1ff578789b6d7e2d37fbfee32b42ae2fd4 /tools/lib | |
parent | 13edc237200c75425ab0e3fe4b4c75dafb468c2e (diff) | |
download | linux-e95770af4c4a280fab2080529d30452a7628d45d.tar.bz2 |
tools api: Add a lightweight buffered reading api
The synthesize benchmark shows the majority of execution time going to
fgets and sscanf, necessary to parse /proc/pid/maps. Add a new buffered
reading library that will be used to replace these calls in a follow-up
CL. Add tests for the library to perf test.
Committer tests:
$ perf test api
63: Test api io : Ok
$
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrey Zhizhikin <andrey.z@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lore.kernel.org/lkml/20200415054050.31645-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/lib')
-rw-r--r-- | tools/lib/api/io.h | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/tools/lib/api/io.h b/tools/lib/api/io.h new file mode 100644 index 000000000000..b7e55b5f8a4a --- /dev/null +++ b/tools/lib/api/io.h @@ -0,0 +1,112 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Lightweight buffered reading library. + * + * Copyright 2019 Google LLC. + */ +#ifndef __API_IO__ +#define __API_IO__ + +struct io { + /* File descriptor being read/ */ + int fd; + /* Size of the read buffer. */ + unsigned int buf_len; + /* Pointer to storage for buffering read. */ + char *buf; + /* End of the storage. */ + char *end; + /* Currently accessed data pointer. */ + char *data; + /* Set true on when the end of file on read error. */ + bool eof; +}; + +static inline void io__init(struct io *io, int fd, + char *buf, unsigned int buf_len) +{ + io->fd = fd; + io->buf_len = buf_len; + io->buf = buf; + io->end = buf; + io->data = buf; + io->eof = false; +} + +/* Reads one character from the "io" file with similar semantics to fgetc. */ +static inline int io__get_char(struct io *io) +{ + char *ptr = io->data; + + if (io->eof) + return -1; + + if (ptr == io->end) { + ssize_t n = read(io->fd, io->buf, io->buf_len); + + if (n <= 0) { + io->eof = true; + return -1; + } + ptr = &io->buf[0]; + io->end = &io->buf[n]; + } + io->data = ptr + 1; + return *ptr; +} + +/* Read a hexadecimal value with no 0x prefix into the out argument hex. If the + * first character isn't hexadecimal returns -2, io->eof returns -1, otherwise + * returns the character after the hexadecimal value which may be -1 for eof. + * If the read value is larger than a u64 the high-order bits will be dropped. + */ +static inline int io__get_hex(struct io *io, __u64 *hex) +{ + bool first_read = true; + + *hex = 0; + while (true) { + int ch = io__get_char(io); + + if (ch < 0) + return ch; + if (ch >= '0' && ch <= '9') + *hex = (*hex << 4) | (ch - '0'); + else if (ch >= 'a' && ch <= 'f') + *hex = (*hex << 4) | (ch - 'a' + 10); + else if (ch >= 'A' && ch <= 'F') + *hex = (*hex << 4) | (ch - 'A' + 10); + else if (first_read) + return -2; + else + return ch; + first_read = false; + } +} + +/* Read a positive decimal value with out argument dec. If the first character + * isn't a decimal returns -2, io->eof returns -1, otherwise returns the + * character after the decimal value which may be -1 for eof. If the read value + * is larger than a u64 the high-order bits will be dropped. + */ +static inline int io__get_dec(struct io *io, __u64 *dec) +{ + bool first_read = true; + + *dec = 0; + while (true) { + int ch = io__get_char(io); + + if (ch < 0) + return ch; + if (ch >= '0' && ch <= '9') + *dec = (*dec * 10) + ch - '0'; + else if (first_read) + return -2; + else + return ch; + first_read = false; + } +} + +#endif /* __API_IO__ */ |