It’s worth a listen though. I talk about some of the features of the new download manager (old news now, but he ask for this interview a while ago…), how I got involved with the Mozilla project, and a few other interesting tidbits including what I’ve currently been working on. There is other interesting things in there too!

I talked to dolske, who happens to be the resident DTrace expert around here. With his help, I was able to put together this little D script to track writes to the files in question, and give me user stack traces so we know who is writing and when. With this, we’ve figured out what was writing, and are working on how to make it write less as we speak.

DTrace really is an awesome tool, even if it can be a bit awkward to use from time to time.

Once I had those logs, I needed some way to parse the files for data so I can use it in a reasonable way. I wrote a python script to parse the strace logs, and then insert them into a sqlite database file (26.8 MB) so I could run some interesting queries on the data.

With that data, I decided to generate some graphs to easily see what was going on. All of these graphs compose the data from the six runs of Firefox that talos ran - the data is all summed up. All the graphs have larger versions available if you click on them.

I figured that the most useful graph for investigating this Ts regression would be execution time:

Note that that is six runs of Firefox, which is why it is as long as it is. Next, I looked at the average execution time for each function call:

And finally, I looked at the number of calls of each of these functions:

We are clearly seeing an increase in the number of fsync calls, and we know that on Linux those can be more painful than they are on other operating systems. My next step is to see if we also see this increase on OS X. If we do, I’m going to assume we see it on windows as well, and get backtraces of every single fsync call to determine why we’ve double the number of calls by upgrading.

I’ll make a new post as more data comes in.

For those of you who are used to running browser tests, you no longer have to worry about adding in the ../browser bits to the path either. The makefile handles it all for you. Hurray!

Boy, some of the initial planning to solve this problem has changed. I found several bugs in my triggers, which made my life not so fun. Now if you google the word fsync, my website is the first result returned (scary!). Never fear, however! I have good news. The places team has put together an experimental build that should help greatly. Before I link to the build though, I have a warning:
Do not use your normal profile - crate a copy of it to test this build. This build will modify the places database schema, and if you go back to a normal build, you will experience some strange behavior.

With that out of the way, the builds can be found here and will be available for the next seven days.

Feedback is not only welcomed, but wanted. You can track the overall progress of this task in bug 442967

For those of your who use GMail (and if you don’t, why not?!), I’m going to strongly suggest you protect yourself from man-in-the-middle attacks by setting the https only mode in Gmail. A MITM attack can steal your login credentials, as well as anything else you transmit in the clear over the Internet (which is pretty much everything) and is easier than you might think.

To do this, open your gmail settings (found at the top right of the page).

Ensure that you have the general tab selected (it’s the leftmost tab).

Scroll down to the bottom to the browser connections section, and make sure you select “always use https”. Feel free to click on the link as well to learn more.

Firefox 3 will always let you know that a page is being transmitted over https by turning the area to the left of the location bar (called the identity button) blue like so:

This is a serious issue. If you have any questions about this, or this type of attack, feel free to ask and I’ll be happy to answer (or find out the answer if I don’t know). Security is serious business, and I want you to be as safe as you can be.

timeless found an interesting flaw to my previous proposal. If you were to visit a page, delete it, and then visit another page not yet seen before, you will never see it in any of your queries. When you flush out all the “deleted” things, it will go away forever (unless the ordering was a bit different than what I expect, but that’s besides the point). This is because of our id selection algorithm used in the insertion triggers.

I ended up talking to dietrich on irc about this, and we decided that deleting isn’t a common case, so we should feel free to do the write (with the needed fsyncs) at that point. As a result, our views change, as well as a few of our triggers.

moz_places_view now looks like this:

SELECT *
FROM moz_places_temp
UNION ALL
SELECT *
FROM moz_places
WHERE id NOT IN (SELECT id FROM moz_places_temp)

And moz_historyvisits_view now looks like this:

SELECT *
FROM moz_historyvisits_temp
UNION ALL
SELECT *
FROM moz_historyvisits
WHERE id NOT IN (SELECT id FROM moz_historyvisits_temp)

The trigger for deletion on moz_places_view now looks like this:

CREATE TEMPORARY TRIGGER moz_places_view_delete_trigger
INSTEAD OF DELETE
ON moz_places_view
BEGIN
  DELETE FROM moz_places_temp
  WHERE id = OLD.id;
  DELETE FROM moz_places
  WHERE id = OLD.id;
END

Lastly, the trigger for deletion on moz_historyvisits_view now looks like this:

CREATE TEMPORARY TRIGGER moz_historyvisits_view_delete_trigger
INSTEAD OF DELETE
ON moz_historyvisits_view
BEGIN
  DELETE FROM moz_historyvisits_temp
  WHERE id = OLD.id;
  DELETE FROM moz_historyvisits
  WHERE id = OLD.id;
  UPDATE moz_places_view
  SET visit_count = visit_count - 1
  WHERE moz_places_view.id = OLD.place_id;
END

The net result is two fewer in-memory tables, and slightly less complicated view queries. There isn’t much of a change with the triggers.

Many thanks to timeless for catching that. If you have any other concerns or spot any issues, please let me know with a comment here, or feel free to send me an e-mail.