Opened on 05/11/2016 at 02:29:54 PM

Closed on 05/11/2016 at 04:21:28 PM

Last modified on 05/11/2016 at 04:23:59 PM

#4036 closed defect (fixed)

Slow addElemHideSelectors performance with Chrome >= 51

Reported by: kzar Assignee: kzar
Priority: P2 Milestone: Adblock-Plus-1.12-for-Chrome-Opera-Safari
Module: Platform Keywords:
Cc: sebastian, mapx, trev, Ross, scheer Blocked By:
Blocking: Platform: Chrome
Ready: yes Confidential: no
Tester: Unknown Verified working: no
Review URL(s):

Description (last modified by kzar)


  • Chrome both Version 51.0.2704.36 beta (64-bit) and Version 52.0.2729.3 dev (64-bit)
  • EasyList subscription with AA enabled
  • Debian Linux Stretch 64bit
  • Thinkpad T450

How to reproduce

  1. Start recording a CPU profile using the Chrome profiling tool.
  2. Open
  3. Once loaded stop recording the profile and take a look.

Observed behaviour

More than 6000ms is spent in the addElemHideSelectors function in the include.preload.js content script.

Expected behaviour

With earlier Chrome versions around 300ms is spent in that function.


  • I couldn't reproduce the issue with either Version 49.0.2623.75 (64-bit) or Version 50.0.2661.94 (64-bit).
  • This seems completely unrelated to issue #235, performance of ElemHide.getSelectorsByDomain() seems to be just as fast with newer Chrome versions.
  • I don't think this is down to a deopt with new Chrome versions, or at least the profiler doesn't show any deoptimisation warnings. (See the attached screenshot.)
  • See related discussion in the forum (Note: The title seems incorrect, it seems that the problem started with version 51 not 50.)
  • The problem seems to be caused by the while loop inside addElemHideSelectors somehow. When that is commented out the problem goes away. (The problem does not go away when only the style.sheet.addRule line is commented so it looks like the problem could be with the line above.)

Attachments (1)

addElemHideSelectors-profile.png (128.0 KB) - added by kzar on 05/11/2016 at 02:30:35 PM.
Screenshot of addElemHideSelectors profiling in Chrome 52

Download all attachments as: .zip

Change History (8)

Changed on 05/11/2016 at 02:30:35 PM by kzar

Screenshot of addElemHideSelectors profiling in Chrome 52

comment:1 Changed on 05/11/2016 at 03:01:14 PM by kzar

  • Description modified (diff)

comment:2 Changed on 05/11/2016 at 03:07:09 PM by kzar

  • Owner set to kzar

comment:3 Changed on 05/11/2016 at 03:34:31 PM by kzar

  • Review URL(s) modified (diff)
  • Status changed from new to reviewing

comment:4 Changed on 05/11/2016 at 03:46:36 PM by sebastian

  • Priority changed from Unknown to P2
  • Ready set

comment:5 Changed on 05/11/2016 at 04:20:22 PM by abpbot

A commit referencing this issue has landed:

comment:6 Changed on 05/11/2016 at 04:21:28 PM by kzar

  • Milestone set to Adblock-Plus-for-Chrome-Opera-Safari-next
  • Resolution set to fixed
  • Status changed from reviewing to closed

comment:7 Changed on 05/11/2016 at 04:23:59 PM by kzar

  • Cc Ross scheer added

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