Yesterday Apple released an, which it claims, among other issues, fixes two prominent ones that resulted in high memory usage and periodic instances where loaded pages would flash white (seen when switching to a different window or at times when interacting with the page).
Unfortunately even though Safari no longer flashes loaded pages white, there may still be instances where you can encounter similar behaviors. With version 5.0, Apple split Safari's process into two components: a main Safari parent program, and a child process called Safari Web Content that is responsible for rendering the scripts and code of your various Web pages.
If Safari Web Content encounters an error, then it may crash and reload. When this happens, the program will notify you of this occurrence, but will reload all of the Web pages in every window and tab, resulting in the pages turning white before loading up. In a similar manner, at times the Safari Web Content process may hang when managing some Web site content, and when you try to load a new page the program will force you to reload all Web content.
It would be nice if Apple could build Safari so each window's content is in its own subprocess, or is otherwise independent from other windows so these types of full application reloads are not as prevalent. However, this wishful thinking may not take into account the hurdles and complexities of how Safari is programmed.
Despite the program still showing some white-screen behaviors, it appears at least in initial testing that Safari's memory usage is significantly lower than the prior version, at least for some users.
I usually keep around 20 Web sites open in various tab combinations, most of which are discussion forums and troubleshooting articles that are generally fairly minimal in terms of media content. Before the Safari 5.1.2 update, the Safari Web Content process in Activity Monitor would regularly use well above 1GB of RAM, which was an exceptional amount for the relatively basic content being displayed.
To test the new version of Safari's RAM usage in comparison to the old one, I set up a standard workflow of mine that consisted of 10 windows with a mix of Apple discussion forum topics, a couple of troubleshooting sites, an instance of Gmail, and a couple of Apple knowledge-base articles. In looking at Activity Monitor after loading the sites, Safari Web Content (the underlying content handling process for Safari) was using 1.27GB with the Safari program itself using 243MB. These values did not change even after clearing Safari's caches and reloading the program.
After installing the Safari 5.1.2 update, I launched the program and loaded the same set of windows and tabs (Lion's Resume feature is very useful for this). Upon checking Activity Monitor the program showed a similar 1.26GB of memory usage; however, after clearing Safari's cache and then reloading the program, the results were much different.
Instead of using well over a gigabyte of memory, Activity Monitor now showed the Safari Web Content process using around 464MB and fluctuating from around 420MB to 470MB. Even after extensive usage it does not come near the 1.26GB it previously used. The Safari program itself (the parent process of Safari Web Content) uses a little less as well, at around 200MB instead of 250MB.
This situation may be specific to my particular setup and the Web sites I visit, and Apple's wording for the update does suggest it addresses only some issues where memory usage was a problem; therefore, other users may not see as much of a change as I noticed. However, if not then there is one step you can take which is to clear some temporary files that could have been created in Safari 5.1.1 which might still be contributing to high memory usage.
If you do not initially see more efficient memory usage after applying the update, try clearing the caches using the option to do so in the Safari menu, but also consider doing this with a third-party maintenance application such as TinkerTool System, OnyX, or Lion Cache Cleaner.
In addition to clearing caches, consider removing the Safari preferences file (called "com.apple.Safari.plist" and located in the /username/Library/Preferences/ directory), and running a permissions fix on the boot drive after installing the Safari 5.1.2 update. These options will potentially clear any access and configuration issues that could be resulting in odd Safari behavior.
What has your experience been with Safari's RAM usage after applying the version 5.1.2 update? Lower? Higher? No difference? Let us know in the comments.