Heschi Kreinick c1903db4db internal/memoize: switch from GC-driven to explicit deletion ... The GC-based cache has given us a number of problems. First, memory leaks driven by reference cycles: the Go runtime cannot collect cycles involving finalizers, which prevents us from writing natural code in Bind callbacks. If we screw it up, we get a mysterious leak that takes a long time to track down. Second, the behavior is generally mysterious; it's hard to predict how long a value lasts, and harder to tell if a value being live is a bug. Third, we think that it may be interacting poorly with the GC, resulting in unnecessary memory usage. The structure of the values we put in the cache is not actually that complicated -- there are only 5 significant types: parse, typecheck, analyze, parse mod, and analyze mod. Managing them manually should not be conceptually difficult, and in fact we already do most of the work in (*snapshot).clone. In this CL the cache adds the concept of "generations", which function as reference counts on cache entries. Entries are still global and shared across generations, but will be explicitly deleted once no generations refer to them. The idea is that each snapshot is a new generation, and can inherit entries from the previous snapshot or leave them behind to be deleted. One obvious risk of this scheme is that we'll leave dangling references to values without actually inheriting them across generations. To prevent that, getting a value requires passing in the generation at which it's being read, and an error will be returned if that generation is dead. Change-Id: I4b30891efd7be4e10f2b84f4c067b0dee43dcf9c Reviewed-on: https://go-review.googlesource.com/c/tools/+/242838 Run-TryBot: Heschi Kreinick <heschi@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Rebecca Stambler <rstambler@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>		2020-08-10 19:02:17 +00:00
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memoize_test.go	internal/memoize: switch from GC-driven to explicit deletion	2020-08-10 19:02:17 +00:00
memoize.go	internal/memoize: switch from GC-driven to explicit deletion	2020-08-10 19:02:17 +00:00