Tool to simulate non-sequential disk I/O (simulate db file sequential read) in C POSIX Post: 302531319

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Top Forums Programming Tool to simulate non-sequential disk I/O (simulate db file sequential read) in C POSIX Post 302531319 by Corona688 on Thursday 16th of June 2011 11:35:51 AM

06-16-2011

Registered User

On Linux:

Code:

#!/bin/bash


for ((N=0; N<10; N++))
do
        dd if=gigabytefile of=/dev/null skip=$((RANDOM % 1024)) bs=$((1024*1024)) count=1
done

Code:

$ ./disktest.sh
$ ./disktest.sh
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0916211 s, 11.4 MB/s
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0867173 s, 12.1 MB/s
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.00175788 s, 597 MB/s
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0166869 s, 62.8 MB/s
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.00172908 s, 606 MB/s
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.018392 s, 57.0 MB/s
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0261557 s, 40.1 MB/s
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0181711 s, 57.7 MB/s
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0152302 s, 68.8 MB/s
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0144154 s, 72.7 MB/s
$

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LEARN ABOUT MOJAVE

memory_pressure

MEMORY_PRESSURE(1)					    BSD General Commands Manual 					MEMORY_PRESSURE(1)

NAME

     memory_pressure -- Tool to apply real or simulate memory pressure on the system.

SYNOPSIS

     memory_pressure [-l level] | [-p percent_free] | [-S -l level]

OPTIONS

     -l <level> Apply real or simulate memory pressure (if specified alongside simulate argument) on the system till low memory notifications cor-
     responding to <level> are generated. Supported values are "warn" and "critical".

     -p <percent_free> Allocate memory till the available memory in the system is <percent_free> of total memory. If the percentage of available
     memory to total memory on the system drops, the tool will free memory till either the desired percentage is achieved or it runs out of memory
     to free.

     -S Simulate memory pressure on the system by placing it artificially for <sleep_seconds> duration at the "warn" or "critical" level.

     -s <sleep_seconds> Duration to wait before allocating or freeing memory if applying real pressure. In case of simulating memory pressure,
     this is the duration the system will be maintained at an artifical memory level.

DESCRIPTION

     A tool to apply real or simulate memory pressure on the system

SEE ALSO

     vm_stat(1)

Mac OS X							    Mar 7, 2013 							  Mac OS X