diff options
| author | Joey Degges <jdegges@gmail.com> | 2010-03-01 10:26:22 +0000 |
|---|---|---|
| committer | Pádraig Brady <P@draigBrady.com> | 2010-03-04 10:42:00 +0000 |
| commit | dae35bac98520c1402d29c60df11a2993889ec85 (patch) | |
| tree | 4f33ab7a30f05d32dacfe2e81079e508b6a206db /m4/jm-macros.m4 | |
| parent | 168a6b6a0fde18e7e1445f189da3994edf3f2aa6 (diff) | |
| download | coreutils-dae35bac98520c1402d29c60df11a2993889ec85.tar.gz | |
sort: inform the system about our input access pattern
Tell the system that we'll access input sequentially,
so that we more efficiently process uncached files in a few cases:
Reading from faster flash devices. E.g. 21 MB/s key:
NORMAL 31.6s (26.8 user)
SEQUENTIAL 27.7s
WILLNEED 27.7s
Processing in parallel with readahead when using a small 1M buffer:
NORMAL 24.7s (21.1 user)
SEQUENTIAL 22.7s
WILLNEED 25.6s
A small benefit when merging:
NORMAL 25.0s (16.9 user)
SEQUENTIAL 24.6s (16.6 user)
WILLNEED 38.4s (13.1 user)
Note WILLNEED is presented above for comparison to show it
has some unwanted characteristics due to its synchronous
prepopulation of the cache. It has a good benefit on a
mechanical disk @ 80MB/s and a multicore system with
competing processes:
NORMAL 14.73s
SEQUENTIAL 10.95s
WILLNEED 05.22s
However the scheduling differences causing this result
are probably best explicitly managed using `nice` etc.
* m4/jm-macros.m4 (coreutils_MACROS): check for posix_fadvise().
* src/sort.c (fadvise_input): A new function to apply
the POSIX_FADV_SEQUENTIAL hint to an input stream.
(stream_open): Call the above function for all input streams.
Diffstat (limited to 'm4/jm-macros.m4')
| -rw-r--r-- | m4/jm-macros.m4 | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/m4/jm-macros.m4 b/m4/jm-macros.m4 index 0ddbf2fdc..d4e20f9c1 100644 --- a/m4/jm-macros.m4 +++ b/m4/jm-macros.m4 @@ -64,6 +64,7 @@ AC_DEFUN([coreutils_MACROS], LIBS=$coreutils_saved_libs # Used by sort.c. + AC_CHECK_FUNCS_ONCE([posix_fadvise]) AC_CHECK_FUNCS_ONCE([nl_langinfo]) # Used by tail.c. |