From 63b5e8164847285f5d3c1dbc9f7c41ad8c17ccc6 Mon Sep 17 00:00:00 2001
From: Pádraig Brady
Date: Wed, 14 Jul 2010 09:49:16 +0100
Subject: fadvise: new module providing a simpler interface to posix_fadvise
* bootstrap.conf: Include the new module
* gl/lib/fadvise.c: Provide a simpler interface to posix_fadvise.
(fadvise): Provide hint to the whole file associated with a stream.
(fdadvise): Provide hint to the specific portion of a file
associated with a file descriptor.
* gl/lib/fadvise.h: Redefine POSIX_FADV_* to FADVISE_* enums.
* gl/modules/fadvise: New file.
* m4/jm-macros.m4: Remove the no longer needed posix_fadvise check.
* .x-sc_program_name: Exclude test-fadvise.c from this check.
* gl/tests/test-fadvise (main): New test program.
* gl/modules/fadvise-testss: A new index to reference the tests.
* src/sort.c (stream_open): Use the new interface.
* src/dd.c (iwrite): Likewise.
---
gl/lib/fadvise.c | 37 +++++++++++++++++++++++++++++
gl/lib/fadvise.h | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 109 insertions(+)
create mode 100644 gl/lib/fadvise.c
create mode 100644 gl/lib/fadvise.h
(limited to 'gl/lib')
diff --git a/gl/lib/fadvise.c b/gl/lib/fadvise.c
new file mode 100644
index 000000000..cf2bc7028
--- /dev/null
+++ b/gl/lib/fadvise.c
@@ -0,0 +1,37 @@
+/* Declare an access pattern hint for files.
+ Copyright (C) 2010 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see . */
+
+#include
+#include "fadvise.h"
+
+#include
+#include
+#include "ignore-value.h"
+
+void
+fdadvise (int fd, off_t offset, off_t len, fadvice_t advice)
+{
+#if HAVE_POSIX_FADVISE
+ ignore_value (posix_fadvise (fd, offset, len, advice));
+#endif
+}
+
+void
+fadvise (FILE *fp, fadvice_t advice)
+{
+ if (fp)
+ fdadvise (fileno (fp), 0, 0, advice);
+}
diff --git a/gl/lib/fadvise.h b/gl/lib/fadvise.h
new file mode 100644
index 000000000..fb84e75c9
--- /dev/null
+++ b/gl/lib/fadvise.h
@@ -0,0 +1,72 @@
+/* Declare an access pattern hint for files.
+ Copyright (C) 2010 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see . */
+
+#include
+#include
+#include
+#include
+
+/* There are a few hints one can provide, which have the
+ following characteristics on Linux 2.6.31 at least.
+
+ POSIX_FADV_SEQUENTIAL
+ Doubles the size of read ahead done for file
+ POSIX_FADV_WILLNEED
+ _synchronously_ prepopulate the buffer cache with the file
+ POSIX_FADV_NOREUSE
+ Could lower priority of data in buffer caches,
+ but currently does nothing.
+ POSIX_FADV_DONTNEED
+ Drop the file from cache.
+ Note this is automatically done when files are unlinked.
+
+ We use this enum "type" both to make it explicit that
+ these options are mutually exclusive, and to discourage
+ the passing of the possibly undefined POSIX_FADV_... values.
+ Note we could #undef the POSIX_FADV_ values, but that would
+ preclude using the posix_fadvise() function with its standard
+ constants. Using posix_fadvise() might be required if the return
+ value is needed, but it must be guarded by appropriate #ifdefs. */
+
+#if HAVE_POSIX_FADVISE
+typedef enum {
+ FADVISE_NORMAL = POSIX_FADV_NORMAL,
+ FADVISE_SEQUENTIAL = POSIX_FADV_SEQUENTIAL,
+ FADVISE_NOREUSE = POSIX_FADV_NOREUSE,
+ FADVISE_DONTNEED = POSIX_FADV_DONTNEED,
+ FADVISE_WILLNEED = POSIX_FADV_WILLNEED,
+ FADVISE_RANDOM = POSIX_FADV_RANDOM,
+} fadvice_t;
+#else
+typedef enum {
+ FADVISE_NORMAL,
+ FADVISE_SEQUENTIAL,
+ FADVISE_NOREUSE,
+ FADVISE_DONTNEED,
+ FADVISE_WILLNEED,
+ FADVISE_RANDOM,
+} fadvice_t;
+#endif
+
+/* We ignore any errors as these hints are only advisory.
+ There is the chance one can pass invalid ADVICE, which will
+ not be indicated, but given the simplicity of the interface
+ this is unlikely. Also not returning errors allows the
+ unconditional passing of descriptors to non standard files,
+ which will just be ignored if unsupported. */
+
+void fdadvise (int fd, off_t offset, off_t len, fadvice_t advice);
+void fadvise (FILE *fp, fadvice_t advice);
--
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