Demystify Your Linux Box !!: vmxnet3 :A New Para-Virtualized NIC from Vmware

Demystify Your Linux Box !!: vmxnet3 :A New Para-Virtualized NIC from Vmware

vmxnet3 :A New Para-Virtualized NIC from Vmware

VMXNET3, the newest generation of virtual network adapter from VMware, offers performance on par with or better than its previous generations in both Windows and Linux guests. Both the driver and the device have been highly tuned to perform better on modern systems. Furthermore, VMXNET3 introduces new features and enhancements, such as TSO6 and RSS.

TSO6 makes it especially useful for users deploying applications that deal with IPv6 traffic, while RSS is helpful for deployments requiring high scalability. All these features give VMXNET3 advantages that are not possible with previous generations of virtual network adapters.
Moving forward, to keep pace with an ever‐increasing demand for network bandwidth, Vmware recommend customers migrate to VMXNET3 if performance is of top concern to their deployments.

The VMXNET3 driver is NAPI‐compliant on Linux guests. NAPI is an interrupt mitigation mechanism that improves high‐speed networking performance on Linux by switching back and forth between interrupt mode and polling mode during packet receive. It is a proven technique to improve CPU efficiency and allows the
guest to process higher packet loads. VMXNET3 also supports Large Receive Offload (LRO) on Linux guests.However, in ESX 4.0 the VMkernel backend supports large receive packets only if the packets originate from another virtual machine running on the same host.

VMXNET3 supports larger Tx/Rx ring buffer sizes compared to previous generations of virtual network devices. This feature benefits certain network workloads with bursty and high‐peak throughput. Having a larger ring size provides extra buffering to better cope with transient packet bursts.

VMXNET3 supports three interrupt modes:

MSI‐X,
MSI, and
INTx.

Normally the VMXNET3 guest driver will attempt to use the interrupt modes in the order given above, if the guest kernel supports them. With VMXNET3, TCP Segmentation Offload (TSO) for IPv6 is supported for both Windows and Linux guests now, and TSO support for IPv4 is added for Solaris guests in addition to Windows and Linux guests.

To use VMXNET3, the user must install VMware Tools on a virtual machine with hardware version 7.

How to Upgrade to Fedora 12?

Last night I thought of upgrading my Fedora 11 to Fedora 12.I went through Fedora Official website and came across a new tool called preupgrade.It went fine and so wanted to share it with you all.

Here we go...

In most cases, the simplest way to upgrade an existing Fedora installation is with the preupgrade tool. When a new version of Fedora is available, preupgrade downloads the packages necessary to upgrade your installation, and initiates the upgrade process.

Install preupgrade with your graphical package manager, or

type yum install preupgrade at the command line and press Enter.

To run preupgrade, type preupgrade at the command line and press Enter.

Note:
If the contents of your /etc/fedora-release file have been changed from the default, your Fedora installation may not be found when attempting an upgrade to Fedora 12.
You can relax some of the checks against this file by booting with the following boot command:

linux upgradeany

Use the linux upgradeany command if your Fedora installation was not given as an option to upgrade.

To perform an upgrade, select Perform an upgrade of an existing installation. Click Next when you are ready to begin your upgrade.

To re-install your system, select Perform a new Fedora installation and refer to Chapter 6, Installing on Intel® and AMD Systems for further instructions.

Understanding /proc/cpuinfo?

A hyperthreaded processor has the same number of function units as an older, non-hyperthreaded processor. It just has two execution contexts, so it can maybe achieve better function unit utilization by letting more than one program execute concurrently. On the other hand, if you're running two programs which compete for the same function units, there is no advantage at all to having both running "concurrently." When one is running, the other is necessarily waiting on the same function units.

A dual core processor literally has two times as many function units as a single-core processor, and can really run two programs concurrently, with no competition for function units.

A dual core processor is built so that both cores share the same level 2 cache. A dual processor (separate physical cpus) system differs in that each cpu will have its own level 2 cache. This may sound like an advantage, and in some situations it can be but in many cases new research and testing shows that the shared cache can be faster when the cpus are sharing the same or very similar tasks.

In general Hyperthreading is considered older technology and is no longer supported in newer cpus. Hyperthreading can provide a marginal (10%) for some server workloads like mysql, but dual core technology has essentially replaced hyperthreading in newer systems.

A dual core cpu running at 3.0Ghz should be faster then a dual cpu (separate core) system running at 3.0Ghz due to the ability to share the cache at higher bus speeds.

The examples below details how we determine what kind of cpu(s) are present.

The kernel data Linux exposes in /proc/cpuinfo will show each logical cpu with a unique processor number. A logical cpu can be a hyperthreading sibling, a shared core in a dual or quad core, or a separate physical cpu. We must look at the siblings, cpu cores and core id to tell the difference.

If the number of cores = the number of siblings for a given physical processor, then hyperthreading is OFF.

/bin/cat /proc/cpuinfo | /bin/egrep 'processor|model name|cache size|core|sibling|physical'

Example 1: Single processor, 1 core, no Hyperthreading

processor : 0
model name : AMD Duron(tm) processor
cache size : 64 KB

Example 2: Single processor, 1 core, Hyperthreading is enabled.

Notice how we have 2 siblings, but only 1 core. The physical cpu id is the same for both: 0.

processor : 0
model name : Intel(R) Pentium(R) 4 CPU 2.80GHz
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 1
processor : 1
model name : Intel(R) Pentium(R) 4 CPU 2.80GHz
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 1


Example 3. Single socket Quad Core

Notice how each processor has its own core id. The number of siblings matches the number of cores so there are no Hyperthreading siblings. Also notice the huge l2 cache - 6 MB. That makes sense though, when considering 4 cores share that l2 cache.

processor : 0
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 0
cpu cores : 4
processor : 1
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 1
cpu cores : 4
processor : 2
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 2
cpu cores : 4
processor : 3
model name : Intel(R) Xeon(R) CPU E5410 @ 2.33GHz
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 3
cpu cores : 4

Example 3a. Single socket Dual Core

Again, each processor has its own core so this is a dual core system.

processor : 0
model name : Intel(R) Pentium(R) D CPU 3.00GHz
cache size : 2048 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
processor : 1
model name : Intel(R) Pentium(R) D CPU 3.00GHz
cache size : 2048 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2

Example 4. Dual Single core CPU, Hyperthreading ENABLED

This example shows that processer 0 and 2 share the same physical cpu and 1 and 3 share the same physical cpu. The number of siblings is twice the number of cores, which is another clue that this is a system with hyperthreading enabled.

processor : 0
model name : Intel(R) Xeon(TM) CPU 3.60GHz
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 1
processor : 1
model name : Intel(R) Xeon(TM) CPU 3.60GHz
cache size : 1024 KB
physical id : 3
siblings : 2
core id : 0
cpu cores : 1
processor : 2
model name : Intel(R) Xeon(TM) CPU 3.60GHz
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 1
processor : 3
model name : Intel(R) Xeon(TM) CPU 3.60GHz
cache size : 1024 KB
physical id : 3
siblings : 2
core id : 0
cpu cores : 1

Example 5. Dual CPU Dual Core No hyperthreading

Of the 5 examples this should be the most capable system processor-wise. There are a total of 4 cores; 2 cores in 2 separate socketed physical cpus. Each core shares the 4MB cache with its sibling core. The higher clock rate (3.0 Ghz vs 2.3Ghz) should offer slightly better performance than example 3.

processor : 0
model name : Intel(R) Xeon(R) CPU 5160 @ 3.00GHz
cache size : 4096 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
processor : 1
model name : Intel(R) Xeon(R) CPU 5160 @ 3.00GHz
cache size : 4096 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2
processor : 2
model name : Intel(R) Xeon(R) CPU 5160 @ 3.00GHz
cache size : 4096 KB
physical id : 3
siblings : 2
core id : 0
cpu cores : 2
processor : 3
model name : Intel(R) Xeon(R) CPU 5160 @ 3.00GHz
cache size : 4096 KB
physical id : 3
siblings : 2
core id : 1
cpu cores : 2

Shell Script: Quick Look into Command-Line Arguments

Following script is used to print command line argument and will show you how to access them:
$ vi demo

#!/bin/sh
#
# Script that demos, command line args
#
echo "Total number of command line argument are $#"
echo "$0 is script name"
echo "$1 is first argument"
echo "$2 is second argument"
echo "All of them are :- $* or $@"

Run it as follows

Set execute permission as follows:

$ chmod 755 demo

Run it & test it as follows:

$ ./demo Hello World

If test successful, copy script to your own bin directory (Install script for private use)
$ cp demo ~/bin

Check whether it is working or not (?)

$ demo
$ demo Hello World

NOTE: After this, for any script you have to used above command, in sequence, I am not going to show you all of the above command(s) for rest of Tutorial.

Shell Script: How to use GREP utility?

The grep command selects and prints lines from a file (or a bunch of files) that match a pattern. Let's say your friend Bill sent you an email recently with his phone number, and you want to call him ASAP to order some books. Instead of launching your email program and sifting through all the messages, you can scan your in-box file, like this:

The most useful grep flags are shown here:

-i Ignore uppercase and lowercase when comparing.
-v Print only lines that do not match the pattern.
-c Print only a count of the matching lines.
-n Display the line number before each matching line.

When grep performs its pattern matching, it expects you to provide a regular expression for the pattern. Regular expressions can be very simple or quite complex, so we won't get into a lot of details here. Here are the most common types of regular expressions:

abc Match lines containing the string "abc" anywhere.
^abc Match lines starting with "abc."
abc$ Match lines ending with "abc."
a..c Match lines containing "a" and "c" separated by any two characters (the dot matches any single character).
a.*c Match lines containing "a" and "c" separated by any number of characters (the dot- asterisk means match zero or more characters).


Regular expressions also come into play when using vi, sed, awk, and other Unix commands. If you want to master Unix, take time to understand regular expressions. Here is a sample poem.txt file and some grep commands to demonstrate regular-expression pattern matching:

Mary had a little lamb
Mary fried a lot of spam
Jack ate a Spam sandwich
Jill had a lamb spamwich

To print all lines containing spam (respecting uppercase and lowercase), enter

grep 'spam' poem.txt
Mary fried a lot of spam
Jill had a lamb spamwich

To print all lines containing spam (ignoring uppercase and lowercase), enter

grep -i 'spam' poem.txt
Mary fried a lot of spam
Jack ate a Spam sandwich
Jill had a lamb spamwich

To print just the number of lines containing the word spam (ignoring uppercase and lowercase), enter

grep -ic 'spam' poem.txt
3

To print all lines not containing spam (ignoring uppercase and lowercase), enter

grep -i -v 'spam' poem.txt
Mary had a little lamb

To print all lines starting with Mary, enter

grep '^Mary' poem.txt
Mary had a little lamb
Mary fried a lot of spam

To print all lines ending with ich, enter

grep 'ich$' poem.txt
Jack ate a Spam sandwich
Jill had a lamb spamwich

To print all lines containing had followed by lamb, enter

grep 'had.*lamb' poem.txt
Mary had a little lamb
Jill had a lamb spamwich

Shell Script: A Simple Cut Command

Today is a sunny day outside and lets tweak with shell scripting.
We will carry on this episode throughout this year. I can assure you will surely be interested with this new episode.

Lets start it from scratch:

Consider a slight variation on the company.data file we've been playing with in this section:

406378:Sales:Itorre:Jan
031762:Marketing:Nasium:Jim
636496:Research:Ancholie:Mel
396082:Sales:Jucacion:Ed


If you want to print just columns 1 to 6 of each line (the employee serial numbers), use the -c1-6 flag, as in this command:

cut -c1-6 company.data
406378
031762
636496
396082

If you want to print just columns 4 and 8 of each line (the first letter of the department and the fourth digit of the serial number), use the -c4,8 flag, as in this command:

cut -c4,8 company.data
3S
7M
4R
0S

And since this file obviously has fields delimited by colons, we can pick out just the last names by specifying the -d: and -f3 flags, like this:

cut -d: -f3 company.data
Itorre
Nasium
Ancholie
Jucacion

Here is a summary of the most common flags for the cut command:

-c [n | n,m | n-m] Specify a single column, multiple columns (separated by a comma), or range of columns (separated by a dash).
-f [n | n,m | n-m] Specify a single field, multiple fields (separated by a comma), or range of fields (separated by a dash).
-dc Specify the field delimiter.
-s Suppress (don't print) lines not containing the delimiter.