Objects returned by Get() are not special in any way. They will be GCd just like an object returned by new(). In fact, they will often be just a new()'d object. There is no association of such an object with the pool. A pool is just a fancy free list. Get might return a previously Put'd object instead of a new() one.
Your scheme is unsafe. Storing a *Object as a uintptr means the underlying Object will be collected out from under your map. On Thursday, September 27, 2018 at 2:15:11 PM UTC-7, Francis wrote: > > Ah, ok. In that case keeping a reference to a *Object in a uintptr will > not prevent it from being garbage collected. > > For each garbage collection cycle the runtime visits every memory > reference that is still 'alive'. Any references which were not visited will > be reclaimed as free memory. > > So if you wrote a map `map[uintptr]bool` the GC will not visit any of the > locations pointed to by any of the `uintptr`s in the map. So they would all > look like unused memory locations, and they would be reclaimed by the > garbage collector. > > So when you went to cast them back into a *Object, you would be pointing > into memory the runtime thought had been freed. > > On Thursday, 27 September 2018 19:52:41 UTC+2, Peter Mogensen wrote: >> >> >> >> On 09/27/2018 07:44 PM, Francis wrote: >> > I believe the pool does not track the objects that it returns from a >> > call to `Get()`. I would be surprised if it did track these objects. >> > There is no real need for it to track these objects. >> >> Exactly, that was my point. Else there would be no reason to call Put() >> >> > I think now your proposal makes a lot more sense to me. If I understand >> > correctly you had understood that the sync.Pool would track all the >> > instances of objects it had created, via Get(), and so they wouldn't be >> > GCed, This would be (to me) a very surprising implementation of >> sync.Pool. >> >> No. My understanding of sync.Pool is that only the objects Put() back >> into it would be subject to GC. (I could of course, just read the source) >> The objects handed out by Get() and still in the hand of the program >> would be the responsibility of the application. >> >> My intention was then to handle that responsibility by temporarily >> storing these pointers as uintptr and by using them as a value in a map, >> be able to exploit the map-of-non-pointers optimization to avoid GC >> scans of the map. >> >> ... and of course remember to Put() back any map entries delete()'ed >> from the map and any entries left before the reference to the map it >> self is forgotten and the map is left to be garbage collected. >> >> /Peter >> >> >> >> -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
