Tag Archive for 'benchmark'

Optimize hard disk performance in Linux; benchmarks on Slicehost

Published
by
Tummblr
on December 15, 2007
in Linux
. 3 Comments

“A three-pronged attack on performance” is a good read on improving performance in Linux. One performance enhancing setting is the hard disk’s readahead value. Unfortunately, there is no magical readahead value that will optimize your hard disk’s performance; you must run your own benchmarks. I used the following code to benchmark disk performance (12 times) at each readahead value on my 256MB Slicehost VPS.

for ((i=0;i<12;i++)); do sudo hdparm -t /dev/sda1; done

The average disk read speeds at each readahead value are as follows:

“hdparm -a128 /dev/sda1″ - 65.69 mb/sec
“hdparm -a256 /dev/sda1″ - 104.44 mb/sec
“hdparm -a512 /dev/sda1″ - 114.54 mb/sec
“hdparm -a1024 /dev/sda1″ - 119.39 mb/sec
“hdparm -a2048 /dev/sda1″ - 122.82 mb/sec

It appears that on my Slicehost VPS, “hdparm -a2048” yields the best performance. To ensure that this readahead value is used at all times, I instruct hdparm to set it on every bootup by adding the following line to /etc/conf.d/local.start

hdparm -a2048 /dev/sda1

More details and documentation on Slicehost’s Wiki.

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PHP: speed of string comparison functions

Published
by
Tummblr
on November 28, 2007
in PHP
. 0 Comments

Here is a recent benchmark of various PHP string comparison functions. Not surprisingly, the fastest is strpos. But did you know that preg_match is faster than strstr and not much slower than strpos? This contradicts the following note in the official PHP manual:

Do not use preg_match() if you only want to check if one string is contained in another string. Use strpos() or strstr() instead as they will be faster.

ereg is by far the slowest.

So, the best function to use to do a simple check to see if a string contains a particular substring is strpos. In all other cases preg_match might be superior to strstr. YMMV.