Bug 131051 - Deleting CodeBlocks should be lazy/incremental
Summary: Deleting CodeBlocks should be lazy/incremental
Status: NEW
Alias: None
Product: WebKit
Classification: Unclassified
Component: JavaScriptCore (show other bugs)
Version: 528+ (Nightly build)
Hardware: Unspecified Unspecified
: P2 Normal
Assignee: Mark Hahnenberg
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2014-04-01 12:07 PDT by Mark Hahnenberg
Modified: 2014-04-03 14:07 PDT (History)
0 users

See Also:

Attachments
work in progress (19.59 KB, patch)
2014-04-02 17:28 PDT, Mark Hahnenberg 		no flags Details | Formatted Diff | Diff
work in progress (32.70 KB, patch)
2014-04-03 14:07 PDT, Mark Hahnenberg 		no flags Details | Formatted Diff | Diff
Show Obsolete (1) View All Add an attachment (proposed patch, testcase, etc.)

Note You need to log in before you can comment on or make changes to this bug.
Description Mark Hahnenberg 2014-04-01 12:07:51 PDT 
Deleting many CodeBlocks synchronously during GC can dramatically increase pause times. We should use a similar approach to JSCell sweeping instead to mitigate these costs.
Comment 1 Mark Hahnenberg 2014-04-02 17:28:47 PDT 
Created attachment 228450 [details]
work in progress
Comment 2 Mark Hahnenberg 2014-04-03 14:07:31 PDT 
Created attachment 228542 [details]
work in progress

Putting this on hold for the moment.

To future me (or whomever picks this up):

There's a couple of issues with this patch.
(1) You need to make sure that no code assumes that m_alternative (and any other referenced CodeBlocks) is in a consistent state. For example, ProfiledCodeBlockJettisoningWatchpoint can fire after clearing the CodeBlock's m_alternative field but before the CodeBlock is fully destroyed (along with the Watchpoint itself).
(2) You also need to make the ref-count of a CodeBlock and its notion of isLive is the same. deleteAllCompiledCode is a tricky thing to get right for this.