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Offer the JavaScript engine an opportunity to perform garbage collection if needed.


JS_MaybeGC(JSContext *cx);
Name Type Description
cx JSContext * The context in which to perform garbage collection, if needed.


JS_MaybeGC tries to determine whether garbage collection in cx's runtime would free up enough memory to be worth the amount of time it would take. If so, it performs some garbage collection.

Calling JS_MaybeGC when the application is idle can help prevent garbage collection from happening at less convenient times. Calling JS_MaybeGC periodically when the application is busy, from a JSBranchCallback or JSOperationCallback Added in SpiderMonkey 1.8, can keep memory usage down and improve performance. Both are good practices. In both cases, frequent calls JS_MaybeGC are safe and will not cause the application to spend a lot of time doing redundant garbage collection work.

Implementation note: SpiderMonkey 1.8 and earlier determine whether garbage collection is appropriate by analyzing statistics about the GC heap and memory usage since the last garbage collection cycle. The analysis is simplistic but produces acceptable performance for many applications. In some applications, JS_MaybeGC collects more often than it should for ideal performance. Such applications can benefit from implementing their own custom-tuned maybe-GC function that conditionally calls JS_GC on the basis of some application-specific analysis, and using that instead of JS_MaybeGC.

To perform a full garbage collection unconditionally, use JS_GC.

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 Contributors to this page: FeRDNYC, arai, fscholz, Jorend, Dria, MMondor
 Last updated by: FeRDNYC,