if you are holding it already plus you don't know what happens after that assertFree(obj) call I am not sure about the value of this assertion.
On Thu, Oct 25, 2012 at 6:04 PM, Alex Russell <[email protected]>wrote: > This use-case is usually what weak refs get pressed into service for. But > I think that answering your question, "why is my RSS continually > increasing?" is something for a tool (debugger, profiler, etc.) to help > answer. Some sort of assertion version of free() seems like the right > thing: it can communicate your intent there be no refs at that point to a > tool. E.g. > > console.assertFree(obj); > > Regards > On Oct 25, 2012 7:58 PM, "Isaac Schlueter" <[email protected]> wrote: > >> On Fri, Oct 26, 2012 at 1:35 AM, Shawn Steele >> <[email protected]> wrote: >> > I sort of have a fundamental problem with the solution. Eg: If it >> were actually unused, it'd be GC'd. Since it isn't GC'd, something must be >> holding a reference to it. So if you force it to be gone, or clear all the >> properties, or whatever, seems to me that then you'd just start throwing >> random errors in the code that tried to use the "freed" object? That might >> be even harder to track down. >> >> On the contrary, "TypeError: Cannot read property 'prop' of >> undefined", with a stack trace, is WAY easier to track down than "The >> RSS on my server gradually rises, until the operating system kills it, >> which happens about every 4 hours." >> >> Fast failure is not as good as success, but it's better than anything >> else. >> >> >> > On Thu, Oct 25, 2012 at 4:16 PM, Isaac Schlueter <[email protected]> wrote: >> >> It'd be really nice if JS had a way to explicitly delete an object. >> > >> > I guess you mean ... a way to set all the refs to a object to undefined. >> >> Yes, exactly. >> >> >> On Fri, Oct 26, 2012 at 1:20 AM, John J Barton >> <[email protected]> wrote: >> >> var obj = {} >> >> var foo = { ref: obj } >> > >> > I assume that in your real life, you don't know 'foo' but somehow you >> > know that foo.ref is never used? >> >> Well, you know that IF foo.ref is used, it's an error, and ought to >> throw. Also, it's quite easy to check if the property exists, and set >> it to a new object if so. It's common to have things like: >> >> if (!this._parser) { >> this._parser = new ParserThingie(); >> } >> >> In this example, imagine that parsers are expensive to create. So, we >> try to reuse them (danger!), and over time, our program grows until we >> have some code paths where the parsers are not getting all of their >> data removed properly. If the parser has a ref to an object that has >> a reference to some other thing, etc., then you've got a memory leak. >> >> This exact situation happened in Node's HTTP library a few months ago, >> and was very tedious to fix. We quite easily identified one of the >> things in the chain, and that it must have been linked in some way to >> an HTTP parser (or else it would have been GC'ed). >> >> It would have been much easier to just find the point where we know >> that the HTTP response object should be "finished", and forcibly >> remove any references to it. >> >> >> > Since you know "obj" can you set it to be a getter that returns >> undefined? >> >> Yeah, but the purpose of this is to take *away* the ref that you >> already *have*. What good is a getter that returns undefined, once >> you've already gotten it? Closing the barn door after the horse has >> left. >> >> >> > Deleting all of the properties of obj would solve the problem as well I >> assume. >> >> But that is a bit more whack-a-mole, and expensive. Ultimately, what >> we did was move all of the addon properties on parsers to a single >> object, and delete that object when we re-use the http parser. >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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