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); -- cgit v1.2.3-70-g09d2