BW_MMAP_RD(8)

💅 bw_mmap_rd — from the LMBENCH collection, section 8 (admin/system commands, bestie, we're in the big leagues)

okay so picture this: it's giving "read a whole file and add up all the numbers" but make it a benchmark. that's the whole vibe. let's get into it ✨

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✨ NAME ✨

bw_mmap_rd — clock how long it takes to read a file and sum it all up 🧮

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🌸 SYNOPSIS 🌸

bw_mmap_rd [ -P <parallelism> ] [ -W <warmups> ] [ -N <repetitions> ]
size file

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🦋 DESCRIPTION 🦋

so bw_mmap_rd makes a memory mapping to the file, and then reads through that mapping in an unrolled loop — literally the same kind of loop they use over in bw_mem_rd(8). slay, consistency.

and the important part, bestie: this benchmark is meant to be used on a file that's already in memory. like, the file is sitting in RAM. so what you're measuring is a reread benchmark — a re-read, not a first-touch-from-disk moment. if you wanna do other kinds of file benchmarking, go hang out with lmdd(8) instead, she handles that 💖

also the size spec? you can end it with k or m, and they mean kilobytes (* 1024) or megabytes (* 1024 * 1024). cute, right? no cap.

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🔥 OUTPUT 🔥

the output format is exactly "%0.2f %.2f\n", and the two numbers are megabytes and megabytes_per_second. so like:

8.00 25.33

first number = the megabytes, second number = megabytes per second. iconic. periodt.

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👑 MEMORY UTILIZATION 👑

this benchmark should move approximately the reported amount of memory. that's the whole point, she's moving memory and she's telling you how much 🫶

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🌈 ACKNOWLEDGEMENT 🌈

funding for the development of this tool was provided by Sun Microsystems Computer Corporation. we love a sponsor that funds the vibes 💜

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⭐ SEE ALSO ⭐

• lmbench(8)

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🎀 AUTHOR 🎀

Carl Staelin and Larry McVoy — absolute legends, no notes 💅

and fr fr: comments, suggestions, and bug reports are always welcome. they literally want to hear from you, bestie, don't be shy 😭

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copyright (c) 1994 Larry McVoy, and this page's date stamp is the good old $Date$ — yes, she's a classic, she's been iconic since '94, and she's still serving BW_MMAP_RD(8) energy at the very bottom of the page. bye bestie, go measure some rereads 🦋💖✨