Date: Sun, 14 Jun 2026 14:27:09 +0000 From: Baptiste Daroussin <bapt@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: ffe47c424e0a - main - grep: periodic timer-based fflush instead of unconditional per-line flush Message-ID: <6a2eba3d.37a89.6e8ac4b2@gitrepo.freebsd.org>
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The branch main has been updated by bapt: URL: https://cgit.FreeBSD.org/src/commit/?id=ffe47c424e0a45f5d8d20a5944477821bd946eef commit ffe47c424e0a45f5d8d20a5944477821bd946eef Author: Baptiste Daroussin <bapt@FreeBSD.org> AuthorDate: 2026-06-12 12:13:35 +0000 Commit: Baptiste Daroussin <bapt@FreeBSD.org> CommitDate: 2026-06-14 14:26:30 +0000 grep: periodic timer-based fflush instead of unconditional per-line flush Replace the unconditional fflush(stdout) in grep_printline and procmatches with a periodic timer that flushes at most once every 100ms. This preserves interactive responsiveness (grep | tee, grep | tail -f) while avoiding 1M+ write(2) syscalls when processing large inputs. The flush interval is tracked via clock_gettime(CLOCK_MONOTONIC) and a static timespec. --line-buffered continues to flush immediately via setlinebuf(3), as before. Benchmark on 1M lines (37MB output to file): unconditional fflush: 1.90s (sys 1.22s) periodic 100ms timer: 0.49s (sys 0.007s) Reviewed by: kevans Differential Revision: https://reviews.freebsd.org/D57528 --- usr.bin/grep/util.c | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) diff --git a/usr.bin/grep/util.c b/usr.bin/grep/util.c index 5b40405852b3..dbb21dcfd78e 100644 --- a/usr.bin/grep/util.c +++ b/usr.bin/grep/util.c @@ -45,6 +45,7 @@ #include <stdio.h> #include <stdlib.h> #include <string.h> +#include <time.h> #include <unistd.h> #include <wchar.h> #include <wctype.h> @@ -724,12 +725,36 @@ grep_strdup(const char *str) * Print an entire line as-is, there are no inline matches to consider. This is * used for printing context. */ -void grep_printline(struct str *line, int sep) { +static struct timespec printline_last_flush = { 0, 0 }; + +static void +flush_if_stalled(void) +{ + struct timespec now; + + if (lbflag && fileeol == '\n') + return; + + clock_gettime(CLOCK_MONOTONIC, &now); + if (now.tv_sec > printline_last_flush.tv_sec || + (now.tv_sec == printline_last_flush.tv_sec && + now.tv_nsec - printline_last_flush.tv_nsec > 100000000)) { + fflush(stdout); + printline_last_flush = now; + } +} + +void +grep_printline(struct str *line, int sep) +{ printline_metadata(line, sep); fwrite(line->dat, line->len, 1, stdout); putchar(fileeol); - fflush(stdout); + if (lbflag) + fflush(stdout); + else + flush_if_stalled(); } static void @@ -836,7 +861,7 @@ printline(struct parsec *pc, int sep, size_t *last_out) *last_out = pc->ln.len; } putchar('\n'); - fflush(stdout); + flush_if_stalled(); } else if (!oflag) { /* * -o is terminated on every match output, so this @@ -847,7 +872,7 @@ printline(struct parsec *pc, int sep, size_t *last_out) */ terminated = false; } else { - fflush(stdout); + flush_if_stalled(); } } else grep_printline(&pc->ln, sep);home | help
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