LMDD(8)

💅 LMDD(8) — the LMBENCH girlies' I/O mover

okay so bestie, this is lmdd, section 8 of the LMBENCH manual. she moves I/O around and tells you how fast it went. that's the whole vibe. let's go 🫶

✨ NAME ✨

lmdd — move io for performance and debugging tests 💫

🌸 SYNOPSIS 🌸

lmdd [ option=value ] ...

🦋 DESCRIPTION 🦋

lmdd copies a specified input file to a specified output, with possible conversions. no cap, that's it. 🎀

the real tea though? this program is primarily useful for timing I/O since it prints out the timing statistics after completing. she's not here to be a file copier, she's here to be a stopwatch with main character energy ⏱️✨

👑 OPTIONS 👑

one bullet per option, all of them, no skipping, periodt 💅

• if=name — input file is taken from name; internal is the default. internal is a special file that acts like Sun's /dev/zero, i.e., it provides a buffer of zeros without doing a system call to get them. the following file names are taken to mean the standard input: -, 0, or stdin. 🍓
• of=name — output file is taken from name; internal is the default. internal is a special file that acts like /dev/null, without doing a system call to get rid of the data. the following file names are taken to mean the standard output: -, 1, or stdout. and the following file names are taken to mean the standard error: 2, or stderr. 🕳️✨
• bs=n — input and output block size n bytes (default 8192). ⚠️ note that this is different from dd(1), which has a 512 byte default — so don't come in here expecting dd's numbers, she's built different. also note that the block size can be followed by k or m to indicate kilo bytes (*1024) or megabytes (*1024*1024), respectively. 🔢
• ipat=n — if n is non zero, expect a known pattern in the file (see opat). mismatches will be displayed as "ERROR: off=%d want=%x got=%x". the pattern is a sequence of 4 byte integers with the first 0, second 1, and so on. the default is not to check for the pattern. 🔍
• opat=n — if n is non zero, generate a known pattern on the output stream. used for debugging file system correctness. the default is not to generate the pattern. 🧪
• mismatch=n — if n is non zero, stop at the first mismatched value. used with ipat. 🛑
• skip=n — skip n input blocks before starting copy. ⏭️
• fsync=n — if n is non-zero, call fsync(2) on the output file before exiting or printing timing statistics. 💾
• sync=n — if n is non-zero, call sync(2) before exiting or printing timing statistics. 🌊
• rand=n — this argument, by default off, turns on random behavior. 🎲 the argument is not a flag, it is a size, and that size is used as the upper bound for the seeks. also note that the block size can be followed by k or m to indicate kilo bytes (*1024) or megabytes (*1024*1024), 📏
• flush=n — if n is non-zero and mmap(2) is available, call msync(2) to invalidate the output file. this flushes the file to disk so that you don't have to unmount/mount. 🧹 it is not as good as mount/unmount because it just flushes file pages — it misses the indirect blocks which are still cached. not supported on all systems, compile time option. 🚧
• rusage=n — if n is non-zero, print rusage statistics as well as timing statistics. not supported on all systems, compile time option. 📊
• count=n — copy only n input records. 🔢

🌈 EXAMPLES 🌈

this is the most common usage, the intent is to measure disk performance. the disk is a spare partition mounted on /spare. 🗂️

# mount /spare
# lmdd if=internal of=/spare/XXX count=1000 fsync=1
7.81 MB in 3.78 seconds (2.0676 MB/sec)

now we flush cache:

# umount /spare
# mount /spare

and read it back, bestie:

# lmdd if=/spare/XXX of=internal
7.81 MB in 2.83 seconds (2.7611 MB/sec)

like… the second run is faster, that's the whole point, she ate 🔥

💖 AUTHOR 💖

Larry McVoy, lm@sun.com 👑

ok that's the page!! go time your disks, you're gonna slay 💅✨

(c)1994 Larry McVoy — $Date$ — and yeah this is LMDD(8) from LMBENCH, mwah 🎀🦋