Uncategorized

HOW TO : Configure Jboss to use hugepages in RHEL/CentOS

Most of us worry about paging to disk (swap), but if you are running a transaction intensive application the paging that happens in RAM also starts to impact the application performance. This happens due to the size of the “block” that is used to store data in memory. Hugepages allows you to store the data in bigger blocks, hence reducing the need to page while interacting with the data.

Here is how you can enable hugepages and configure jboss (actually any Java app) to use hugepages on a RHEL/CentoOS system.

OS CONFIGURATION

  1. Check if your system is capable of supporting hugepages by running[code]grep HUGETLB /boot/config-`uname -r`[/code]

    If you see the response as below, you should be good[code]CONFIG_HUGETLBFS=y
    CONFIG_HUGETLB_PAGE=y
    [/code]

  • Next check if huge pages are already being used by running[code]cat /proc/sys/vm/nr_hugepages [/code]
  1. If the response is anything other than 0, that means hugepages have already been configured.
  • Find the block size for hugepages by running[code]cat /proc/meminfo | grep -i hugepagesize [/code]
  • Calculate the amount of memory you want to dedicate to hugepages. (note: memory allocated to hugepages cannot be used by other processes in the system, unless they are configured to use it)
  1. For example, I want to dedicate 3GB of RAM for hugepages. So the number of hugepages would be[code](3*1024*1024)/2048[/code]
  • Configure the number of hugepages on the system by editing the /etc/sysctl.conf and adding the option[code]vm.nr_hugepages = 1536[/code]

    (note: I put in 1536 since that was the value I got from the above example)

  • Restart the server and check if hugepages has been enabled by running[code]cat /proc/meminfo | grep -i huge [/code]
  1. You should see something like this[code]AnonHugePages:    839680 kB
    HugePages_Total:    1500
    HugePages_Free:     1500
    HugePages_Rsvd:        0
    HugePages_Surp:        0
    Hugepagesize:       2048 kB
    [/code]

JBOSS CONFIGURATION

  1. At this point your system is configured with hugepages and any application that is configured to use them can leverage them.  In this example, we want to configure Jboss to utilize these hugepages
  2. Add the groupid of the user that Jboss is running under to the /etc/sysctl.conf file. In my case, the jboss user group had a GID of 505, so I added this line to /etc/sysctl.conf[code]vm.hugetlb_shm_group = 505 [/code]
  3. Next allocate the memory to the user by editing /etc/security/limits.conf and allocating the memory. Again, in my case, I added the following to /etc/security/limits.conf[code]# Allocate memory for Jboss user to take advantage of hugepages
    jboss   soft    memlock 1500
    jboss   hard    memlock 1500
    [/code]
  4. Finally add the following to the Jboss startup parameters. I edited the $JBOSS_HOME/bin/run.sh file. (note: the startup file can be different based on your config) with the option[code] -XX:+UseLargePages[/code]
  5. Restart Jboss and you are good to go

note : A lot articles that I read online say that hugepages are effective when you are allocating large amounts of RAM to the application. The use case of just using 3GB above was just that.. a use case.

While I cannot personally vouch for it, a lot of users have noted that they saw >2 fold increase in performance.

April 17, 2012 by HOWTO Linux Technology Uncategorized Web 6

HOW TO : Sync git clients across workstations using dropbox

I have recently started using git as a source control for the various scrips that I write. As I also mentioned in this post, I use dropbox to synchronize my data across workstations. Here is my setup for synchronizing git clients across multiple workstations using the same SSH keys (note: this is not a recommended setup from a security prospective. you are recommended to generate different SSH key pairs per workstation to ensure one key getting lost doesn’t compromise your entire account).

  1. Workstation 1
    1. create a directory under your dropbox root, that you want to use as your git home directory. Say DROPBOX/git
    2. Install Git for Windows, or whatever git client you want to use
    3. Change the home path on the git client by executing [code]HOME=’PATH_TO_DROPBOX/DROPBOX/git’ [/code]
    4. Check if the home path has been changed by executing [code]echo $HOME[/code]
    5. Create your SSH keys and configure your public key on the git server
  2. Workstation 2
    1. Repeat and rinse step 1 – 4 specified for workstation 1. You don’t need to create the SSH keys since the other clients will recognize the keys that dropbox would have synced up.
April 15, 2012 by HOWTO Programming Technology Uncategorized 0

Project Uptime : Progress Report 6 : Tweaking Varnish

The server has held up pretty well, since the installation of varnish. Based on this wiki post, I added the following to /etc/varnish/default.vcl

[code]
<pre>
# Drop any cookies sent to WordPress.
sub vcl_recv {
if (!(req.url ~ "wp-(login|admin)")) {
unset req.http.cookie;
}
}

# Drop any cookies WordPress tries to send back to the client.
sub vcl_fetch {
if (!(req.url ~ "wp-(login|admin)")) {
unset beresp.http.set-cookie;
}
}
[/code]

I think the comments are pretty self explanatory.

April 14, 2012 by Technology Uncategorized Web 0

Thank you Mr.Tramiel, for introducing me to the world of computers..

When I was ~9 years old, my dad bought home a Commodore 64K. It was slow.. it was terrible graphics and it took for ever to load a program using it’s “tape” drive. But boy was it fascinating to load up basic and write your own programs!!. I can’t say how many summer hours were spent staring at the screen and trying to get things to work.

Looking back, I can say that I probably wouldn’t have been in the technology field, if not for that first taste of computing.

Thank you Mr.Tramiel. RIP.

April 10, 2012 by Technology Uncategorized 0

HOW TO : Redirect web traffic based on URL patterns in Apache

Apache configuration to redirect traffic to a particular URL based on the pattern in the URL (AKA URI). In this particular example, I want to redirect any traffic that does not have the URL starting with /application or /content to redirect to https://domain_name/application

  • Enable the rewrite module in Apache
  • Add the following conditions in the conf file[code]RewriteCond %{REQUEST_URI} !^/(application|content) [NC]
    RewriteRule ^/(.*) https://%{HTTP_HOST}/application [R,L]
    [/code]

Explanation of the rule

  • ! implies match if the string is not found
  • ^ implies start of string
  • | implies OR
  • [NC] implies not case sensitive (no case)
  • The rule will be triggered if the conditions match
  • [R,L] means external (client side) redirection and last rule to process
April 9, 2012 by HOWTO Uncategorized Web 0

Viva la resistance

I have a confession to make.. I like Big Macs and Krispy Kreme Donuts :). And they have contributed heavily to the increase in my .. hmm.. how do I say this.. mid section :). Plus, it doesn’t help that there is a Krispy Kreme factory and a McDonald’s right on my way to work. And add on to the fact that I haven’t been running for the last year or so, I am proud to say that I have joined the >65% of Americans that are obese.

On my way to work yesterday, I was thinking about what shape (physically) I would be in when Virat grows up. I am sure he doesn’t want to have a dad that can’t play some hoops with him :).

So here’s my 2 month resolution. I am starting with a couple of months because there is a good chance that it might become a habit and then go from there :).

  • Exercise for 30 minutes a day (7 days a week)
  • Eat dessert only once a week
  • No krispy kreme
  • No Big Mac
  • No fries
  • No pop

For every pledge I break, I am going to leave work at 5:00 PM for a week. Believe me when I say that is a tough punishment :). You see.. I love what I do :).

Viva La Resistance!!!

April 6, 2012 by Food Resolutions Running Uncategorized 0