Thank you for Ubuntu 9.10

Just upgraded to Ubuntu 9.10 and everything works. I mean everything that bothered me, just works now. Among huge amount of improvements there is one that I am really happy about. I have two 24" monitors and one on the right I like to keep vertical, so I can read the page w/o scrolling. I accomplished it in Ubuntu 9.04 but had to do all kind of hacks in my xorg.conf, etc. The result was also not perfect, since there were all kind of flickering on the screen, which drove me up the walls. I am happy to say that with Ubuntu 9.10, it just works using standard display configuration panel. Also I was able to align the displays so when half of the window is on the left monitor and half is on the right, the window does not look crooked. Thank you Ubuntu Team!

I/O write speed benchmark

At work we had some performance issues with one of our production boxes. I thought it was related to the I/O on the veritas file system which we have to use for high availability. In order to prove it I needed a tool to write 1K block and flush it, fast. I've searched around on the web and could not find anything that measures only writes, so I wrote one in Clojure. I had to make sure that it is fast and does not generate to much garbage in the main tight loop. New transient was a perfect choice for it. Transients only available in Clojure 1.1.0, so you will need to get the latest alpha.

The main loop is pretty straight forward.

(defn write-to-file [#^String file]
  (with-open [s (FileOutputStream. file)]
    (loop [i 0 r (transient [])]
      (if (< i 1e3)
        (recur (inc i) (conj! r (with-time
                                    (doto s
                                      (.write test-row)
                                      (.flush)))))
        (persistent! r)))))

Here is the gist of the rest.

I've used incanter to plot the data.
And this is one of the plots that I've got, when I ran it on my MacBook Pro.
As you can see there is quite a bit of jitter and that will affect latency. On our production Linux servers after tuning the file system, those jitters almost disappeared. The next step is to use Real-Time OS and RTSJ.