Use posix_fadvise() on input files, where available.

Makefile.am

@@ -102,4 +102,4 @@ analyse: $(pv_SOURCES:.c=.e) FORCE
 FORCE:
 
 clean-local:
-	rm -f $(pv_SOURCES:.c=.e)
+	rm -f src/*/*.e

configure.ac

@@ -20,7 +20,7 @@ AC_CHECK_FUNCS([getopt_long])
 AC_CHECK_HEADERS([getopt.h])
 AC_CHECK_FUNCS([memcpy basename vsnprintf strlcat])
 AC_CHECK_FUNCS([fdatasync])
-AC_CHECK_FUNCS([fpathconf sysconf posix_memalign])
+AC_CHECK_FUNCS([fpathconf sysconf posix_memalign posix_fadvise])
 AC_CHECK_HEADERS([limits.h])
 AC_CHECK_HEADERS([wctype.h])
 AC_CHECK_HEADERS([termios.h])

doc/NEWS.md

@@ -1,6 +1,7 @@
 0.0.20230828-UNRELEASED
 
   * feature: new "`--enable-static`" option to "`configure`" for static builds ([#75](https://codeberg.org/a-j-wood/pv/pull/75))
+  * feature: now uses `posix_fadvise()` like `cat`(1) does, to improve efficiency ([#39](https://codeberg.org/a-j-wood/pv/issues/39))
   * security: with "`--pidfile`", write to a temporary file and rename it into place, to improve security
   * security: keep self-contained copies of name and format string in PV internal state for memory safety
   * cleanup: switched the build system to GNU Automake

doc/TODO.md

@@ -27,7 +27,6 @@ Feature requests
  * ([#36](https://codeberg.org/a-j-wood/pv/issues/36)) Ignore *SIGWINCH* (window size change) if "`-w`" / "`-H`" provided
  * ([#37](https://codeberg.org/a-j-wood/pv/issues/37)) Allow "`-E`" to take a block size argument so errors cause a skip to the next block (Anthony DeRobertis - Oct 2016)
  * ([#38](https://codeberg.org/a-j-wood/pv/issues/38)) Reset ETA on *SIGUSR1* (Jacek Wielemborek - Jan 2019)
- * ([#39](https://codeberg.org/a-j-wood/pv/issues/39)) Use `posix_fadvise()` like `cat`(1) does (Jacek Wielemborek - Oct 2015)
  * ([#40](https://codeberg.org/a-j-wood/pv/issues/40)) Permit "`-c`" with "`-d PID:FD`", reject "`-N`" with "`-d PID`" (Norman Rasmussen - Nov 2020)
  * ([#41](https://codeberg.org/a-j-wood/pv/issues/41)) Improve how backwards-moving reads are shown in "`--watchfd`" (Ryan Cooley - Dec 2017)
  * ([#42](https://codeberg.org/a-j-wood/pv/issues/42)) Option to discard stdin so nothing is written to stdout (André Stapf - Apr 2017)

src/include/config.h.in

@@ -61,6 +61,9 @@
 /* Define to 1 if you have the <minix/config.h> header file. */
 #undef HAVE_MINIX_CONFIG_H
 
+/* Define to 1 if you have the `posix_fadvise' function. */
+#undef HAVE_POSIX_FADVISE
+
 /* Define to 1 if you have the `posix_memalign' function. */
 #undef HAVE_POSIX_MEMALIGN
 

src/pv/file.c

@@ -165,6 +165,11 @@ unsigned long long pv_calc_total_size(pvstate_t state)
 			return total;
 		}
 
+#if HAVE_POSIX_FADVISE
+		/* Advise the OS that we will only be reading sequentially. */
+		(void) posix_fadvise(fd, 0, 0, POSIX_FADV_SEQUENTIAL);
+#endif
+
 		while (1) {
 			unsigned char scanbuf[1024];
 			int numread, j;
@@ -275,6 +280,7 @@ int pv_next_file(pvstate_t state, int filenum, int oldfd)
 	if (0 == strcmp(state->input_files[filenum], "-")) {
 		state->current_file = "(stdin)";
 	}
+
 #ifdef O_DIRECT
 	/*
 	 * Set or clear O_DIRECT on the file descriptor.

src/pv/loop.c

@@ -114,6 +114,12 @@ int pv_main_loop(pvstate_t state)
 			pv_crs_fini(state);
 		return state->exit_status;
 	}
+
+#if HAVE_POSIX_FADVISE
+	/* Advise the OS that we will only be reading sequentially. */
+	(void) posix_fadvise(fd, 0, 0, POSIX_FADV_SEQUENTIAL);
+#endif
+
 #ifdef O_DIRECT
 	/*
 	 * Set or clear O_DIRECT on the output.