Web Apocrypha

64 bit systems allow allocating more memory, but this extra space has a trade-of: the pointers are grown to 64 bit wide which increases the total memory consumption. Ever wondered about the price of 64 bit? Well, you can find comparisons here about some popular pages on the Qt port of WebKit. Furthermore, we offer some CSS subsystem related comparisons at the end of the post.

Profiling memory consumption is difficult, since most tools just collect a huge amount of unordered data, throw it on you, and be happy. This was motivated me to create a new tool for valgrind called Freya. This tool offered a way to better organize the results. Unfortunately it was not updated for a long time. Now that valgrind 3.6.1 is out, I decided to continue the project: move to the latest valgrind and fix all known bugs (thanks for reporting them).

The measurement performed on a machine which has both 32 and 64 bit environments of the same Linux distribution. The configuration file for Freya is in the attachments section. Since the numbers are peak memory consumptions, the total is not necessary equal to the sum of the sub-totals. It is usually lower. Enough talk now, here are the numbers:

Let's start with www.google.com on a 32 | 64 bit system.
Total: 5.0Mb | 7.5Mb

Libs: 1.8Mb | 3.2Mb
ld: 1.7Mb | 3.0Mb

WebKit: 1.7Mb | 2.4Mb

JavaScriptCore: 1.1Mb | 1.6Mb
Loader: 291.2Kb | 312.5Kb
Other: 161.1Kb | 233.7Kb
CSS-all: 152.1Kb | 216.5Kb
CSS: 130.1Kb | 169.4Kb
CSS-parser: 54.3Kb | 74.5Kb

Page: 109.0Kb | 181.4Kb
Rendering: 38.6Kb | 67.3Kb

Qt: 1.4Mb | 1.8Mb

QtGui: 1.0Mb | 1.2Mb
QtCore: 760.2Kb | 904.4Kb
QtOther: 22.0Kb | 36.0Kb

Other: 227.5Kb | 291.0Kb

Let's continue with www.facebook.com on a 32 | 64 bit system.

Total: 9.7Mb | 12.5Mb

Qt: 5.6Mb | 6.1Mb
QtGui: 4.6Mb | 4.8Mb
QtCore: 1.2Mb | 1.4Mb
QtOther: 20.2Kb | 56.7Kb

WebKit: 3.4Mb | 4.8Mb

JavaScriptCore: 1.9Mb | 2.8Mb
Loader: 737.4Kb | 778.1Kb
CSS-all: 686.1Kb | 1.0Mb
CSS: 513.5Kb
CSS-parser: 257.6Kb

Page: 246.5Kb | 415.1Kb
Other: 153.9Kb | 220.1Kb
Rendering: 69.9Kb | 109.8Kb

Libs: 1.8Mb | 3.2Mb

ld: 1.6Mb | 3.0Mb

Other: 348.2Kb | 401.3Kb

The next one is www.bbc.co.uk on a 32 | 64 bit system. More color-ful
Total: 19.2Mb | 24.8Mb

WebKit: 9.5Mb | 13.0Mb
JavaScriptCore: 6.2Mb | 8.2Mb
Loader: 1.4Mb | 1.6Mb
CSS-all: 874.5Kb | 1.2Mb
CSS: 674.0Kb | 957.1Kb
CSS-parser: 283.2Kb | 455.8Kb

Page: 786.8Kb | 1.3Mb
Rendering: 403.0Kb | 655.4Kb
Other: 380.6Kb | 462.2Kb

Qt: 7.5Mb | 8.2Mb

QtGui: 5.4Mb | 5.7Mb
QtCore: 1.9Mb | 2.1Mb
QtOther: 547.8Kb | 585.7Kb

Libs: 1.8Mb | 3.2Mb

ld: 1.7Mb | 3.0Mb

Other: 536.9Kb | 642.8Kb

Git manual (http://www.kernel.org/pub/software/scm/git/docs/user-manual.html) on a 32 | 64 bit system.
Total: 6.8Mb | 10.4Mb

WebKit: 3.3Mb | 5.0Mb
Rendering: 1.3Mb | 2.2Mb
Page: 1.0Mb | 1.6Mb
CSS-all: 463.0Kb | 611.8Kb
CSS: 431.8Kb | 553.2Kb
CSS-parser: 54.3Kb | 74.5Kb

Loader: 359.3Kb | 332.5Kb
Other: 95.9Kb | 149.2Kb
JavaScriptCore: 23.3Kb | 27.7Kb

Libs: 1.8Mb | 3.2Mb

ld: 1.7Mb | 3.0Mb

Qt: 1.5Mb | 1.9Mb

QtGui: 1.0Mb | 1.2Mb
QtCore: 927.6Kb | 1.1Mb

Other: 232.7Kb | 309.8Kb

The Last one is us.battle.net/sc2 on a 32 | 64 bit system. This page is really eye-candy.
Total: 25.3Mb | 28.1Mb

Qt: 20.8Mb | 21.1Mb
QtGui: 19.7Mb | 19.9Mb
QtOther: 1.8Mb | 1.8Mb (libqjpeg: 1.7Mb on both)
QtCore: 1.7Mb | 2.0Mb

WebKit: 7.5Mb | 9.5Mb

JavaScriptCore: 4.3Mb | 5.5Mb
Loader: 1.4Mb | 1.5Mb
Other: 1.2Mb | 1.2Mb
CSS-all: 692.7Kb | 1.0Mb
CSS: 530.8Kb | 744.6Kb
CSS-parser: 103.5Kb | 342.2Kb

Page: 298.6Kb | 488.5Kb
Rendering: 142.0Kb | 234.7Kb

Libs: 1.9Mb | 3.2Mb

ld: 1.7Mb | 3.0Mb

Other: 395.8Kb | 516.2Kb

We thought before that the CSS plays a bigger role in the memory consumption, but it seems the opposite is true. The major player is JavaScriptCore with its ExecutableAllocator and garbage collected areas. Naturally images can consumes a huge amount of memory, but this depends on the page.