Sipe Project

SIPE Project

This project develops a third-party plugin for the Pidgin multi-protocol instant messenger. It implements the extended version of SIP/SIMPLE used by various products:

With this plugin you should be able to replace your Microsoft Office Communicator client with Pidgin.

The source code and Windows installation packages are available on the download page. Various OS distributions offer installation packages under the name pidgin-sipe.

Installation instruction      Note:  When i was compiling from source Configure gave me this error:  “No package ‘libxml-2.0’ found”  if you are running debian system than you need to install “libxml2-dev” instead of libxml-2.0.

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Optimizing Apache for low memory usage

Optimizing Apache for low memory usage

The biggest problem with Apache is the amount of ram is uses. I’ll discuss the following techniques for speeding up Apache and lowering the ram used.

  • Loading Fewer Modules
  • Handle Fewer Simultaneous Requests
  • Recycle Apache Processes
  • Use KeepAlives, but not for too long
  • Lower your timeout
  • Log less
  • Don’t Resolve Hostnames
  • Don’t use .htaccess

Loading Fewer Modules

First things first, get rid of unnecessary modules. Look through your config files and see what modules you might be loading. Are you using CGI? Perl? If you’re not using modules, by all means, don’t load them. That will save you some ram, but the BIGGEST impact is in how Apache handles multiple requests.

Handle Fewer Simultaneous Requests

The more processes apache is allowed to run, the more simultaneous requests it can serve. As you increase that number, you increase the amount of ram that apache will take. Looking at TOP would suggest that each apache process takes up quite a bit of ram. However, there are a lot of shared libraries being used, so you can run some processes, you just can’t run a lot. With Debian 3.1 and Apache2, the following lines are the default:

StartServers 5
MinSpareServers 5
MaxSpareServers 10
MaxClients 20
MaxRequestsPerChild 0

I haven’t found documentation on this, but prefork.c seems to be the module that’s loaded to handle things w/ Apache2 and Debian 3.1. Other mechanisms could or could not be much more memory efficient, but I’m not digging that deep, yet. I’d like to know more, though, so post a comment and let me know. Anyway, the settings that have worked for me are:

StartServers 1
MinSpareServers 1
MaxSpareServers 5
MaxClients 5
MaxRequestsPerChild 300

What I’m basically saying is, “set the maximum amount of requests that this server can handle at any one time to 5.” This is pretty low, and I wouldn’t try to do this on a high volume server. However, there is something you can and should do on your webservers to get the most out of them, whether you’re going for low memory or not. That is tweak the keepalive timeout.

Recycle Apache Processes

If you noticed, I changed the MaxRequestsPerChild variable to 500, from 0. This variable tells Apache how many requests a given child process can handle before it should be killed. You want to kill processes, because different page requests will allocate more memory. If a script allocates a lot of memory, the Apache process under which it runs will allocate that memory, and it won’t let it go. If you’re bumping up against the memory limit of your system, this could cause you to have unnecessary swapping. Different people use different settings here. How to set this is probably a function of the traffic you receive and the nature of your site. Use your brain on this one.

Use KeepAlives, but not for too long

Keepalives are a way to have a persistent connection between a browser and a server. Originally, HTTP was envisioned as being “stateless.” Prior to keepalive, every image, javascript, frame, etc. on your pages had to be requested using a separate connection to the server. When keepalives came into wide use with HTTP/1.1, web browsers were able to keep a connection to a server open, in order to transfer multiple files across that same connection. Fewer connections, less overhead, more performance. There’s one thing wrong, though. Apache, by default, keeps the connections open for a bit too long. The default seems to be 15 seconds, but you can get by easily with 2 or 3 seconds.

This is saying, “when a browser stops requesting files, wait for X seconds before terminating the connection.” If you’re on a decent connection, 3 seconds is more than enough time to wait for the browser to make additional requests. The only reason I can think of for setting a higher KeepAliveTimeout is to keep a connection open for the NEXT page request. That is, user downloads page, renders completely, clicks another link. A timeout of 15 would be appropriate for a site that has people clicking from page to page, very often. If you’re running a low volume site where people click, read, click, etc., you probably don’t have this. You’re essentially taking 1 or more apache processes and saying, “for the next 15 seconds, don’t listen to anyone but this one guy, who may or may not actually ask for anything.” The server is optimizing one case at the expense of all the other people who are hopefully hitting your site.

Lower Your Timeout

Also, just in case, since you’re limiting the number of processes, you don’t want one to be “stuck” timing out for too long, so i suggest you lower your “normal” Timeout variable as well.

Log Less

If you’re trying to maximize performance, you can definitely log less. Modules such as Mod_Rewrite will log debugging info. If you don’t need the debugging info, get rid of it. The Rewrite log is set with the RewriteLog command. Also, if you don’t care about looking at certain statistics, you can choose to not log certain things, like theUser-Agent or the Http-Referer. I like seeing those things, but it’s up to you.
Don’t Resolve Hostnames

This one’s easy. Don’t do reverse lookups inside Apache. I can’t think of a good reason to do it. Any self respecting log parser can do this offline, in the background.

HostnameLookups Off

Don’t Use .htaccess

You’ve probably seen the AllowOverride None command. This says, “don’t look for .htaccess files” Using .htaccess will cause Apache to 1) look for files frequently and 2) parse the .htaccess file for each request. If you need per-directory changes, make the changes inside your main Apache configuration file, not in .htaccess.
Well, that’s it for Part 1, I’ll be back soon with Part 2, where I’ll talk about MySQL optimization & possibly a few other things that crop up.

Credits: http://emergent.urbanpug.com/?p=60

apache performance tuning

Linus torvalds about PAE

PAE really really sucks.

The biggest single reason to go 64-bit is exactly because of physical address space. Your virtual address space needs to bea multiple of the physical one: when you hit 1GB of RAM, 32-bit virtual memory is no longer acceptable. You literally do need more virtual memory than physical.

PAE turned that very simple fact on its head, and screwed things up royally. Whoever came up with the idea was totally incompetent, and had forgotten all the DOS HIGHMEM pains. There’s a damn good reason why we left the 286 behind, and started using 386′s, instead of having HIGHMEM crap with windows into a bigger physical space.

Repeat after me:

virtual space needs to be bigger than physical space. Not “as big”. Not “smaller”. It needs to be bigger, by a factor of at least two, and that’s quite frankly pushing it, and you’re much better off having a factor of ten or more.

Anybody who doesn’t get that is a moron. End of discussion.

Reasons for why you need a bigger virtual space:

– you need to map that physical memory somehow, and no, tiny windows into the physical memory simply do not cut it! If you cannot have normal pointers to the physical space, it immediately means that you need to jump through serious hoops to get there.

– you additionally need to be able to remap things in alternate ways (ie user space) or make space for non-memory issues (virtual page tables, IO, you name it)

Ergo, a factor-of-two is a requirement. PAE was a total and utter disaster.

Yes, Linux supported it, and probably did so better than anybody else. But “better than anybody else” still wasn’t very good. Because you couldn’t use normal pointers to point to arbitrary physical memory, all the memory that couldn’t be accessed directly (ie anythign that didn’t fit in the virtual address map, which also had the user space memory in it) was basically limited to “special uses only”.

So you could allocate user pages in it, but you had huge problems with things like internal kernel data structures, which can be the bulk of your memory needs under some (not that unusual) loads. Directory caches, inodes, etc couldn’t use it, and in general it meant that under Linux, if you had more than 4GB of physical memory, you generally ran into problems (since only 25% of memory was available for normal kernel stuff – the rest had to be addressed through small holes in the tiny virtual address space).

I’m not at all surprised that Windows didn’t push PAE either. It was a total braindamage. I bet they supported it in the server offerings just because they had to, and I bet they did a much worse job of it than Linux did, and the reason you can do that with servers is that the loads are much easier, and you can expect maintainers to set magic config entries to tweak it to make it appear to work well for any particular load, when in reality it is fragile as hell and works only with duct-tape and prayers.

That kind of “duct-tape and prayers and lots of specialized knowledge about the load” is simply not possible in a desktop environment. Yeah, users have prayers, but they lack the duct-tape and the knowledge to work around the problems.

And dammit, in this age and date when almost everybody has a gigabyte of RAM in any new machine, anybody who still thinks that “not that many people need 64-bits” is simply not aware of what he’s speaking of.

Go back and play with HIGHMEM.SYS on a 286, and stop blathering crap. When you’ve spent the last ten years of your life working with HIGHMEM.SYS, then you can come back and tell me that we still don’t need 64 bits. Until that is the case, anybody who still doesn’t get why 64 bits is a requirement should just shut up rather than make a total fool of himself.

So repeat after me: PAE didn’t ever really fix anything. It was a mistake. It was just a total failure, and the result of hw engineers not understanding software.

So no, PAE does not mean that you can use more than 4GB of RAM. Even before PAE, the practical limit was around 1GB, and PAE didn’t move that post a fraction of an inch!

Linus

Link

hidden gnome fish

  1. Open the Run Application dialog (Alt + F2)
  2. Enter “free the fish” (without the quotes)
  3. Press Enter

Another way to invoke it:

  1. Right-click your Gnome panel
  2. Click About Panels
  3. Press the “F” key three times

And another easter egg (really lame, but this one is easy to quit):

  1. Open the Run Application dialog (Alt + F2)
  2. Enter “gegls from outer space” (without the quotes)
  3. Press Enter

Generate strong password inside bash shell

We can easily generate strong password directly from our terminal by adding this line to our ~/.bashrc file.

genpass() {
        local l=$1
        [ "$l" == "" ] && l=20
        tr -dc A-Za-z0-9_ < /dev/urandom | head -c ${l} | xargs
}

After we need to reload bashrc:

source ~/.bashrc

run genpass command in terminal and you will get randomly generated 20 symbol password.