A web browser memory usage comparison was recently posted a the Dot Net Pearls website that compared the memory usage of the Google browser Google Chrome, Mozilla Firefox, Opera 10 and Safari. The web browsers were configured to open 30 tabs over the command line which where then closed manually by the author except for one. A script running in the background recorded the memory usage of all processes during that time which were then used in the comparison.

The results of the web browser memory usage benchmark were then divided into three chars displaying the maximum, average and final memory used by each of the tested web browsers. The Mozilla Firefox web browser used the lowest amount of computer memory of all tested web browsers while the Google Chrome browser showed very high maximum and average memory usage.

And here is where the tester got it wrong. To compute the memory usage all processes where taken into consideration which effectively meant double-counting the shared memory for each process. As the Chromium blog points out:

If you’re measuring memory in a multi-process application like Google Chrome, don’t forget to take into account shared memory. If you add the size of each process via the Windows XP task manager, you’ll be double counting the shared memory for each process. If there are a large number of processes, double-counting can account for 30-40% extra memory size.

To make it easy to summarize multi-process memory usage, Google Chrome provides the “about:memory” page which includes a detailed breakdown of Google Chrome’s memory usage and also provides basic comparisons to other browsers that are running.

Google Chrome’s result would still be higher than that of Firefox even after the adjustments but this is one of the trade-offs of a multi-process browser (which Google Chrome is). You would get the same result with Microsoft’s Internet Explorer 8 if the tester would have tested that web browser as well. This was apparently not possible due to technical difficulties.

Another aspect that needs to be mentioned is the test result of the Opera web browser. Opera is using an automatic setting called Automatic RAM Cache that is enabled by default. This allocated about 10% of the computer memory by default and should be disabled in memory benchmarks. Opera would most likely still have been beaten by Firefox but the gap would probably have been lower.

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