Can we enhance the heuristic to require that a certain number of allocations in the old context must have been made to force a GC?
-- Vitaly On Wed, Sep 23, 2009 at 11:38 AM, Darin Fisher <[email protected]> wrote: > What can we do about the negative performance impact this is having on > chrome extensions? > -Darin > > On Tue, Sep 22, 2009 at 12:57 PM, Erik Corry <[email protected]> wrote: >> >> >> 2009/9/22 Matt Perry <[email protected]> >>> >>> First, my question: what is the reason for the call >>> to i::Heap::CollectAllGarbageIfContextDisposed() in v8::Context::New? Is it >>> just a heuristic that can be removed? Or can we maybe add an API to disable >>> this in some cases? >> >> It's a heuristic. The idea is that when you navigate to a new page you >> will destroy a series of contexts (one per iframe) and then create a new >> context for the new main page. This is a good time to GC because it helps >> clear up the DOM nodes from the old page. >> >>> >>> The Chrome extension system introduces a feature called content scripts, >>> which allows you to run scripts in a new Context with a handle to the DOM >>> window of a target frame. The way this is implemented seems to trigger a >>> pathological case in v8::Context::New, causing more GCs than necessary. >>> What happens is that content scripts create short-lived Contexts, where >>> we create the Context, run some script, and immediately Dispose of it. The >>> call to Dispose sets a flag in v8 which causes the next call to >>> v8::Context::New to trigger a GC. This means that any time 2+ content >>> scripts are run in a given process, we do a GC, slowing down page load. >>> You can see the effect of running 50 content scripts on Chrome's startup >>> here: http://build.chromium.org/buildbot/perf/xp-release/startup/report.html?history=20 (the >>> top green line). If I comment out the call >>> to i::Heap::CollectAllGarbageIfContextDisposed(), the startup time for that >>> test is cut in half. >>> >> >> >> >> -- >> Erik Corry, Software Engineer >> Google Denmark ApS. CVR nr. 28 86 69 84 >> c/o Philip & Partners, 7 Vognmagergade, P.O. Box 2227, DK-1018 Copenhagen >> K, Denmark. >> >> > > > > > --~--~---------~--~----~------------~-------~--~----~ v8-dev mailing list [email protected] http://groups.google.com/group/v8-dev -~----------~----~----~----~------~----~------~--~---
