diff options
Diffstat (limited to 'src/filemanager/ioblksize.h')
| -rw-r--r-- | src/filemanager/ioblksize.h | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/src/filemanager/ioblksize.h b/src/filemanager/ioblksize.h new file mode 100644 index 0000000..91aa633 --- /dev/null +++ b/src/filemanager/ioblksize.h @@ -0,0 +1,86 @@ +/* I/O block size definitions for coreutils + Copyright (C) 1989-2016 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 <http://www.gnu.org/licenses/>. */ + +/* Include this file _after_ system headers if possible. */ + +/* sys/stat.h will already have been included by system.h. */ +#include "lib/stat-size.h" + +/* *INDENT-OFF* */ + +/* As of May 2014, 128KiB is determined to be the minimum + blksize to best minimize system call overhead. + This can be tested with this script: + + for i in $(seq 0 10); do + bs=$((1024*2**$i)) + printf "%7s=" $bs + timeout --foreground -sINT 2 \ + dd bs=$bs if=/dev/zero of=/dev/null 2>&1 \ + | sed -n 's/.* \([0-9.]* [GM]B\/s\)/\1/p' + done + + With the results shown for these systems: + system #1: 1.7GHz pentium-m with 400MHz DDR2 RAM, arch=i686 + system #2: 2.1GHz i3-2310M with 1333MHz DDR3 RAM, arch=x86_64 + system #3: 3.2GHz i7-970 with 1333MHz DDR3, arch=x86_64 + system #4: 2.20GHz Xeon E5-2660 with 1333MHz DDR3, arch=x86_64 + system #5: 2.30GHz i7-3615QM with 1600MHz DDR3, arch=x86_64 + system #6: 1.30GHz i5-4250U with 1-channel 1600MHz DDR3, arch=x86_64 + system #7: 3.55GHz IBM,8231-E2B with 1066MHz DDR3, POWER7 revision 2.1 + + per-system transfer rate (GB/s) + blksize #1 #2 #3 #4 #5 #6 #7 + ------------------------------------------------------------------------ + 1024 .73 1.7 2.6 .64 1.0 2.5 1.3 + 2048 1.3 3.0 4.4 1.2 2.0 4.4 2.5 + 4096 2.4 5.1 6.5 2.3 3.7 7.4 4.8 + 8192 3.5 7.3 8.5 4.0 6.0 10.4 9.2 + 16384 3.9 9.4 10.1 6.3 8.3 13.3 16.8 + 32768 5.2 9.9 11.1 8.1 10.7 13.2 28.0 + 65536 5.3 11.2 12.0 10.6 12.8 16.1 41.4 + 131072 5.5 11.8 12.3 12.1 14.0 16.7 54.8 + 262144 5.7 11.6 12.5 12.3 14.7 16.4 40.0 + 524288 5.7 11.4 12.5 12.1 14.7 15.5 34.5 + 1048576 5.8 11.4 12.6 12.2 14.9 15.7 36.5 + + + Note that this is to minimize system call overhead. + Other values may be appropriate to minimize file system + or disk overhead. For example on my current GNU/Linux system + the readahead setting is 128KiB which was read using: + + file="." + device=$(df --output=source --local "$file" | tail -n1) + echo $(( $(blockdev --getra $device) * 512 )) + + However there isn't a portable way to get the above. + In the future we could use the above method if available + and default to io_blksize() if not. + */ + + +enum { IO_BUFSIZE = 128 * 1024 }; + +/* *INDENT-ON* */ + +static inline size_t +io_blksize (struct stat sb) +{ + size_t blksize = ST_BLKSIZE (sb); + + return MAX (IO_BUFSIZE, blksize); +} |