All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=809961

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=ca9bcb841c46b869aa43bd30dc9c8fd4325a63312a9104afed18d54b2cf3a3e5


Bot(s) for this bug's original alert(s):

chromium-rel-mac12
linux-release

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/14ac27b1840000

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/14ac27b1840000

Configure TaskScheduler to use one less worker than cores by default. by gab@chromium.org
chromium @ f61636f214c9a53a91906a2ec4b35af511bb5b57

Understanding performance regressions:
  http://g.co/ChromePerformanceRegressions

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/14eba2c5840000

📍 Couldn't reproduce a difference.
https://pinpoint-dot-chromeperf.appspot.com/job/14eba2c5840000

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/14a8f1c5840000

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/14a8f1c5840000

Configure TaskScheduler to use one less worker than cores by default. by gab@chromium.org
chromium @ f61636f214c9a53a91906a2ec4b35af511bb5b57

Understanding performance regressions:
  http://g.co/ChromePerformanceRegressions

Tentative fix @ https://chromium-review.googlesource.com/c/v8/v8/+/911670

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/8996e262cc880d6d12ac7dc468964e6313fde023

commit 8996e262cc880d6d12ac7dc468964e6313fde023
Author: Gabriel Charette <gab@chromium.org>
Date: Mon Feb 12 18:07:09 2018

Fix 'num cores' in ConcurrentMarking as well.

This is a follow-up to https://chromium-review.googlesource.com/904662
as I forgot this callsite there. The perf tests still haven't recovered
from decreasing the worker count by 1 to account for main thread
( crbug.com/809961 ) and I assume this line is at fault.

If this is correct, it also indicates ConcurrentMarking as a great
area to focus since a single extra worker appears to be making a
significant difference.

R=mlippautz@chromium.org

Bug:  chromium:809961 ,  chromium:808028 
Change-Id: I9df933a4193fb25ea4e857f589e2164c8a2859b4
Reviewed-on: https://chromium-review.googlesource.com/911670
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51249}
[modify] https://crrev.com/8996e262cc880d6d12ac7dc468964e6313fde023/src/heap/concurrent-marking.cc

All graphs have recovered with the last change (in chromium r536207).

 Issue 812162  has been merged into this issue.

This had also regressed Octane/Splay : https://chromeperf.appspot.com/report?sid=1baa537b4453e72066ada181dbd4d17629d5042e919106baf5d522ca6153f715

(graph has yet to catch up but expected to be fixed as well)