Skip to main content

free command and options


Free command is frontend to /proc/meminfo file. It provide more human readable output to show you the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel:
$ free -m

vmstat command

===========================================

The vmstat, sar and iostat commands are the collection of package included in sysstat – the system monitoring tools. vmstat - Report virtual memory statistics. It reports information about processes, memory, paging, block IO, traps, disks and cpu activity. The  first report produced gives averages since the last reboot.  Additional reports give information on a sampling period of length delay.
Type the following command:
$vmstat
vmstat.png
FIELD DESCRIPTION FOR VM MODE
  Procs
      r: The number of runnable processes (running or waiting for run time).
      b: The number of processes in uninterruptible sleep.
  Memory
      swpd: the amount of virtual memory used.
      free: the amount of idle memory.
      buff: the amount of memory used as buffers.
      cache: the amount of memory used as cache.
      inact: the amount of inactive memory.  (-a option)
      active: the amount of active memory.  (-a option)
  Swap
      si: Amount of memory swapped in from disk (/s).
      so: Amount of memory swapped to disk (/s).
  IO
      bi: Blocks received from a block device (blocks/s).
      bo: Blocks sent to a block device (blocks/s).
  System
      in: The number of interrupts per second, including the clock.
      cs: The number of context switches per second.
Two important fields are free under memory and si, so under swap column
  1. Free – Amount of free/idle memory spaces.
  2. si – Swapped in every second from disk in Kilo Bytes.
  3. so – Swapped out every second to disk in Kilo Bytes.
OPTIONS
delay  The delay between updates in seconds.  If no delay is specified, only one report is printed with the average values since boot.
count  Number of updates.  In absence of count, when delay is defined, default is infinite.

Execute vmstat ‘X’ seconds and (‘N’ number of times)

$ vmstat 3 5

With this command, vmstat execute every 3 seconds and stop after executing 5 intervals.
Screenshot from 2015-07-22 10:30:41.png

-s, --stats Displays a table of various event counters and memory statistics.  This display does not repeat.
$ vmstat -s
Screenshot from 2015-07-22 10:32:12.png
-S, --unit character Switches outputs between 1000 (k), 1024 (K), 1000000 (m), or 1048576 (M) bytes.  Note this does not change the swap (si/so) or block
             (bi/bo) fields.
The vmstat displays in Megabytes with parameters -S and m. By default vmstat displays statistics in kilobytes.
$ vmstat -S m
Screenshot from 2015-07-22 10:36:29.png
    -d, --disk Report disk statistics
        $ vmstat -d
        Screenshot from 2015-07-22 10:42:07.png
Labels:

Popular posts from this blog

Using chrome console to test xPath and css selectors

Since the advent of selenium there have been many plugin to test xPath / css selectors but you don’t need any of them if you have chrome browser. Using Chrome console you can test both xPath and css selectors. Launch website to be tested in chrome browser and hit F-12 and you would see chrome console opened in lower pane of application - Hit escape key and console would open another pane to write element locators - And now you can start writing xPath or css selectors in chrome console and test them - The syntax for writing css id - $$(“ ”) And hit the enter key. If your expression is right then html snippet of the application element corresponding to the css selector would be displayed - If you mouse over the html snippet in chrome console then it would highlight the corresponding element in application - If you want to clean console of previously written element selectors then just hit ctrl+L keys and chrome console would be empty again. Pro
Read more

Verify email confirmation using Selenium

Email confirmation seems to be integral part of any registration process. I came across an application which lets you provide your email address. You can follow the sign up link in you mail and then complete the registration process. Lets consider we provide GMail address for it. Now if were to use only Selenium then we would have to follow following steps - Launch GMail using Selenium; Some how search for new mail in the list of available mails; Some how click on it; Parse the mail message; Get the registration link; Follow up with registration process What do you think of an approach in which you can
14 comments
Read more

Return only first or last element from webelements collection

We often come across situation when there are multiple elements on a page and we probably like to exercise only a few of them using selenium webdriver. May be just first and last element. For example on a search result page we may like to click on only first and last link and not all. This is when Iterables API comes handy. (By the way I am assuming that you have already completed watching selenium training videos :)). Once we have collection of web element then we can use Iterables to get only first or last element as following - Consider that we fetch collection of element as - List< WebElement > webElements = getDriver().findElements(By. id ( "htmlID" ));   Now we can get the first web element from this collection as -  WebElement firstElement = Iterables. getFirst (webElements,  getDriver().findElement(By. id ( "defaultElement" )));   Herein second argument -   (getDriver().findElement(By. id ( "defaultElement" )))    in the me
2 comments
Read more