As the website ( https://wiki.mozilla.org/Performance/MemShrink ) describes, MemShrink is a project to reduce Firefox memory consumption. Summary (taken from the webpage) is
- Speed. Firefox will be faster due to less cache pressure, less paging, and fewer/smaller GC and CC pauses. Changes that reduce memory consumption but make Firefox slower are not desirable.
- Stability. Firefox will suffer fewer aborts/crashes due to virtual or physical memory exhaustion. The former is mostly a problem on 32-bit Windows builds with a 2GB or 4GB virtual memory limit, the latter is mostly a problem on mobile devices that lack swap space.
The engineers working on MemShrink asked the Metrics team to help discover and quantify what variables affect variables that related to MemShrink. Key among these is RESIDENT_MEMORY which is the resident memory that Firefox occupies. For a given installation, multiple measurements are taken before the data is submitted. The data, for a given installation, is recorded as a histogram (so we dont have serial correlations between observations …), and the final value used in modeling is the weighted mean.
More discussion and the full analysis can be found at : http://people.mozilla.org/~sguha/memshrink.analysis.html . In short, there is a lot of variation in the data and the variables used do a poor job explaining the variance in the data. That said,
- version 11 reduces memory consumption about 2% (on average, but keep in mind there is a lot of variation) over FF10
- version 12 ups it by about 11% over v.10 (see the distribution at top of log of RESIDENT_MEMORY by version)
- Presence of Firebug extension causes a slight increase (on average of 12%) but the difference decreases with FF12.
- if one doubles the number of addons (and add 1 to this) the RESIDENT_MEMORY increases by approximately 33%
For more details and plots see http://people.mozilla.org/~sguha/memshrink.analysis.html .