Looking into firefox threads calling fsync()

Looking into firefox threads calling fsync()

I've been looking into fsync calls made by firefox to understand how
efficient it is with regards to filesystems.
I used strace to track the fsync calls made by the threads of firefox over
a browsing session and here's what I've found,
Total number of calls made - http://i.imgur.com/ZstXCuO.png
Calls made by each thread - http://imgur.com/8Ymb1bn.png
Sorry about the links. It seems you need atleast 10 reputation to add photos.
Though firefox created ~90 threads over the session, only 12 made fsync()
calls.
Now how do I go about finding the specific function of these threads?
Like, is the thread a tab, or is it some background firefox process? Where
should I start looking?
Rephrasing the question to help anyone out in the future, how do you find
the specific function of a firefox thread?
Any input/tips will be greatly appreciated!