From f21c51fbd0fa4d7e0d416b994d4bfda5a4370540 Mon Sep 17 00:00:00 2001 From: Carlo Alberto Ferraris Date: Sat, 25 Mar 2017 14:35:07 +0900 Subject: [PATCH] use posix_fadvise to prefetch files when creating archives --- src/common.h | 2 ++ src/create.c | 1 + src/misc.c | 13 +++++++++++++ src/sparse.c | 1 + 4 files changed, 17 insertions(+) diff --git a/src/common.h b/src/common.h index 99a1dd8..f084e04 100644 --- a/src/common.h +++ b/src/common.h @@ -724,6 +724,8 @@ void *page_aligned_alloc (void **ptr, size_t size); int set_file_atime (int fd, int parentfd, char const *file, struct timespec atime); +void prefetch(int fd, off_t offset, size_t len); + /* Module names.c. */ extern size_t name_count; diff --git a/src/create.c b/src/create.c index 18e98d2..60800ec 100644 --- a/src/create.c +++ b/src/create.c @@ -1064,6 +1064,7 @@ dump_regular_file (int fd, struct tar_stat_info *st) finish_header (st, blk, block_ordinal); + prefetch(fd, 0, st->stat.st_size); mv_begin_write (st->file_name, st->stat.st_size, st->stat.st_size); while (size_left > 0) { diff --git a/src/misc.c b/src/misc.c index 632de29..72d8e30 100644 --- a/src/misc.c +++ b/src/misc.c @@ -24,6 +24,7 @@ #include #include #include +#include #ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT # define DOUBLE_SLASH_IS_DISTINCT_ROOT 0 @@ -1248,3 +1249,15 @@ tar_savedir (const char *name, int must_exist) return ret; } + +/* Opportunistally signal to the OS that we are soon going to sequentially read + once a byte range from fd. If not supported or signaling to the OS fails this + function should then behave as a no-op. +*/ +void +prefetch(int fd, off_t offset, size_t len) +{ +#if _XOPEN_SOURCE >= 600 || _POSIX_C_SOURCE >= 200112L + posix_fadvise(fd, offset, len, POSIX_FADV_WILLNEED|POSIX_FADV_SEQUENTIAL|POSIX_FADV_NOREUSE); +#endif +} diff --git a/src/sparse.c b/src/sparse.c index b3a3fd3..0fbd159 100644 --- a/src/sparse.c +++ b/src/sparse.c @@ -503,6 +503,7 @@ sparse_dump_file (int fd, struct tar_stat_info *st) { size_t i; + prefetch(fd, 0, file.stat_info->stat.st_size); mv_begin_write (file.stat_info->file_name, file.stat_info->stat.st_size, file.stat_info->archive_file_size - file.dumped_size); -- 2.12.1