Some time in 2006 a friend who was spending time in Cork Ireland sent me a partial copy of an album called “In the Moon” by a band called “Elephant.” I fell in love and ordered 3 original copies which had to be shipped to the U.S. from Cork. At the time it felt a little rash, but the album is really something and I knew the band had broken up, the album was already scarce.

Fast forward a few years. Stuart Murdoch of Belle and Sebastian released “God Help the Girl” a couple of days ago. I excitedly picked up the album on vinyl during lunch today and this evening I settled in to listen all the way through. Within seconds I recognized the new female singer’s voice – Catherine Ireton from Elephants! I always wanted to hear her do more but I didn’t think it’d ever happen. Her rendition of the classic Belle and Sebastian song “Act of the Apostle” is amazing and she’s stunning on the new title track, “God Help the Girl.” Figures that Stuart would have such excellent taste!

About a year ago I was looking at our Mac OS X XPCOM local file implementation in Gecko and I noticed that it is pretty inefficient in terms of the number of system calls it makes for some common operations. I put optimizing that on my to-do list and I’ve now committed most of the big optimizations. Here are the results.

I tested a Firefox 3.6 nightly build (6/24/2009) against Firefox 3.5rc2 by recording all of the filesystem-related system calls each build made during the course of a full standalone talos Ts run. This talos test essentially launches and quits the browser over and over again (about 23 times). I recorded the filesystem-related system calls using the following command:

sudo fs_usage -e -f filesys | grep firefox-bin > ~/Desktop/call_log.txt

The high-level result is that there were 13% fewer filesystem-related system calls made by the Firefox 3.6 nightly build (184,609 vs. 212,253). Most of my optimizations involved moving to a single “stat” system call to get information instead of using Carbon and Cocoa APIs, which often make multiple system calls, particularly if they involve using Carbon FSRefs. Given my intent, it was unsurprising that the Firefox 3.6 nightly build made 32,344 calls to “stat” vs. 15,134 calls for Firefox 3.5rc2. That is a price worth paying for having the Firefox 3.6 nightly build make only 38,250 calls to “getattrlist” vs. 98,965 calls for Firefox 3.5rc2. In case you’re unfamiliar with “getattrlist,” its man page says “you can think of getattrlist() as a seriously enhanced version of stat(2).”

Here are some other results which are interesting because they give you a good idea of how often Firefox makes certain calls. I omitted some less interesting system calls that were made fewer than 3,000 times apiece.

15,134 stat, Firefox 3.5rc2
32,344 stat, Firefox 3.6 nightly

98,965 getattrlist, Firefox 3.5rc2
38,250 getattrlist, Firefox 3.6 nightly

14,290 open, Firefox 3.5rc2
14,196 open, Firefox 3.6 nightly

9,027 write, Firefox 3.5rc2
8,649 write, Firefox 3.6 nightly

20,643 read, Firefox 3.5rc2
20,245 read, Firefox 3.6 nightly

1,325 pread, Firefox 3.5rc2
1,052 pread, Firefox 3.6 nightly

12,230 lseek, Firefox 3.5rc2
11,787 lseek, Firefox 3.6 nightly

7,692 fcntl, Firefox 3.5rc2
7,214 fcntl, Firefox 3.6 nightly

2,096 mmap, Firefox 3.5rc2
1,950 mmap, Firefox 3.6 nightly