Bug 155460 – Reduce generated JSON HeapSnapshot size

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Joseph Pecoraro]

* SUMMARY
Reduce generated JSON HeapSnapshot size.

Do some extra processing while generating the HeapSnapshot JSON to reduce size. I saw a 10% JSON size reduction on large pages (31.4 MB -> 28.0 MB).

This:
  - removes duplicated edges
  - sorts edges in a reliable order
  - remove edge name duplication
  - avoid multiple cell->identifier lookups by replacing JSCell* with identifiers in Edge structs
  - clears data as early as possible to reduce backend memory footprint during JSON building

[Joseph Pecoraro]

Created attachment 274022 [details]
[PATCH] Proposed Fix

[Geoffrey Garen]

Comment on attachment 274022 [details]
[PATCH] Proposed Fix

Do we have a benchmark that shows the reduction here?

[Joseph Pecoraro]

(In reply to comment #2)
> Comment on attachment 274022 [details]
> [PATCH] Proposed Fix
> 
> Do we have a benchmark that shows the reduction here?

No, I just logged the JSON snapshot string for some very large web pages (I mostly focused on iCloud.com).

I could add a JavaScriptCore/tests/heapProfiler test that creates a lot of objects and measures the generateHeapSnapshot() string length. I shied away from this because it would need to be fuzzy as JavaScriptCore changes. Is there a better way to test this?

[WebKit Commit Bot]

Comment on attachment 274022 [details]
[PATCH] Proposed Fix

Clearing flags on attachment: 274022

Committed r198159: <http://trac.webkit.org/changeset/198159>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.