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For perf's IO intensive internal (non-rigorous) benchmarks there's a near 8% improvement to kallsyms-parsing with a default build. Before: ``` $ perf bench internals all Computing performance of single threaded perf event synthesis by synthesizing events on the perf process itself: Average synthesis took: 146.322 usec (+- 0.305 usec) Average num. events: 61.000 (+- 0.000) Average time per event 2.399 usec Average data synthesis took: 145.056 usec (+- 0.155 usec) Average num. events: 329.000 (+- 0.000) Average time per event 0.441 usec Average kallsyms__parse took: 162.313 ms (+- 0.599 ms) ... Computing performance of sysfs PMU event scan for 100 times Average core PMU scanning took: 53.720 usec (+- 7.823 usec) Average PMU scanning took: 375.145 usec (+- 23.974 usec) ``` After: ``` $ perf bench internals all Computing performance of single threaded perf event synthesis by synthesizing events on the perf process itself: Average synthesis took: 127.829 usec (+- 0.079 usec) Average num. events: 61.000 (+- 0.000) Average time per event 2.096 usec Average data synthesis took: 133.652 usec (+- 0.101 usec) Average num. events: 327.000 (+- 0.000) Average time per event 0.409 usec Average kallsyms__parse took: 150.415 ms (+- 0.313 ms) ... Computing performance of sysfs PMU event scan for 100 times Average core PMU scanning took: 47.790 usec (+- 1.178 usec) Average PMU scanning took: 376.945 usec (+- 23.683 usec) ``` Signed-off-by: Ian Rogers --- tools/lib/api/io.h | 69 +++++++++++++++++++++++++--------------------- 1 file changed, 38 insertions(+), 31 deletions(-) diff --git a/tools/lib/api/io.h b/tools/lib/api/io.h index 84adf8102018..d3eb04d1bc89 100644 --- a/tools/lib/api/io.h +++ b/tools/lib/api/io.h @@ -43,48 +43,55 @@ static inline void io__init(struct io *io, int fd, io->eof = false; } -/* Reads one character from the "io" file with similar semantics to fgetc. */ -static inline int io__get_char(struct io *io) +/* Read from fd filling the buffer. Called when io->data == io->end. */ +static inline int io__fill_buffer(struct io *io) { - char *ptr = io->data; + ssize_t n; if (io->eof) return -1; - if (ptr == io->end) { - ssize_t n; - - if (io->timeout_ms != 0) { - struct pollfd pfds[] = { - { - .fd = io->fd, - .events = POLLIN, - }, - }; - - n = poll(pfds, 1, io->timeout_ms); - if (n == 0) - errno = ETIMEDOUT; - if (n > 0 && !(pfds[0].revents & POLLIN)) { - errno = EIO; - n = -1; - } - if (n <= 0) { - io->eof = true; - return -1; - } + if (io->timeout_ms != 0) { + struct pollfd pfds[] = { + { + .fd = io->fd, + .events = POLLIN, + }, + }; + + n = poll(pfds, 1, io->timeout_ms); + if (n == 0) + errno = ETIMEDOUT; + if (n > 0 && !(pfds[0].revents & POLLIN)) { + errno = EIO; + n = -1; } - 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; + n = read(io->fd, io->buf, io->buf_len); + + if (n <= 0) { + io->eof = true; + return -1; + } + io->data = &io->buf[0]; + io->end = &io->buf[n]; + return 0; +} + +/* Reads one character from the "io" file with similar semantics to fgetc. */ +static inline int io__get_char(struct io *io) +{ + if (io->data == io->end) { + int ret = io__fill_buffer(io); + + if (ret) + return ret; + } + return *io->data++; } /* Read a hexadecimal value with no 0x prefix into the out argument hex. If the -- 2.45.0.rc1.225.g2a3ae87e7f-goog