Bug 100877

Summary:

MarkedBlocks should use something other than the mark bits to indicate liveness for newly allocated objects

Product:

WebKit

Reporter:

Mark Hahnenberg <mhahnenberg>

Component:

JavaScriptCore

Assignee:

Mark Hahnenberg <mhahnenberg>

Status:

RESOLVED FIXED

Severity:

Normal

CC:

webkit.review.bot

Priority:

Version:

528+ (Nightly build)

Hardware:

Unspecified

OS:

Unspecified

Attachments:

Description	Flags
Patch	none
Patch	none
Patch	none

Mark Hahnenberg

Reported 2012-10-31 12:32:32 PDT

Currently when we canonicalize cell liveness data in MarkedBlocks, we set the mark bit for every cell in the block except for those in the free list. This allows us to consider objects that were allocated since the previous collection to be considered live until they have a chance to be properly marked by the collector. If we want to use the mark bits to signify other types of information, e.g. using sticky mark bits for generational collection, we will have to keep track of newly allocated objects in a different fashion when we canonicalize cell liveness. One method would be to allocate a separate set of bits while canonicalizing liveness data. These bits would track the newly allocated objects in the block separately from those objects who had already been marked. We would then check these bits, along with the mark bits, when determining liveness. At the end of the conservative scan, we then throw away these Bitmaps.

Attachments
Patch (10.21 KB, patch) 2012-10-31 12:40 PDT, Mark Hahnenberg	no flags	Details Formatted Diff Diff
Patch (9.71 KB, patch) 2012-11-02 12:43 PDT, Mark Hahnenberg	no flags	Details Formatted Diff Diff
Patch (9.71 KB, patch) 2012-11-02 13:06 PDT, Mark Hahnenberg	no flags	Details Formatted Diff Diff
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