The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/2c75616028e75883e28df2c6d8dd2a6bfe47f718

commit 2c75616028e75883e28df2c6d8dd2a6bfe47f718
Author: Ulan Degenbaev <ulan@chromium.org>
Date: Thu Oct 05 14:38:31 2017

[heap] Ensure progress in unmapping memory chunks.

If sweeping is not making progress and there are many young generation
GCs happening, then this can lead to accumulation of memory chunks in
the unmapper queue.

Bug:  chromium:771966 
Change-Id: Ief73ada0d17198a80b668850c6d2e7ea413113e7
Reviewed-on: https://chromium-review.googlesource.com/702479
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48312}
[modify] https://crrev.com/2c75616028e75883e28df2c6d8dd2a6bfe47f718/src/heap/heap.cc
[modify] https://crrev.com/2c75616028e75883e28df2c6d8dd2a6bfe47f718/src/heap/spaces.h

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/676c41321a948c08d6a43de43fe9b1d60ae81c00

commit 676c41321a948c08d6a43de43fe9b1d60ae81c00
Author: Ulan Degenbaev <ulan@chromium.org>
Date: Thu Oct 05 16:21:12 2017

[heap] Fix threshold for delayed chunks after 2c7561.

Bug:  chromium:771966 
Change-Id: Iac5ee55c0d31de477f21f091f4be015a1ca8d00c
Reviewed-on: https://chromium-review.googlesource.com/702382
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48316}
[modify] https://crrev.com/676c41321a948c08d6a43de43fe9b1d60ae81c00/src/heap/heap.cc

I'll request merge to 60-62 once this gets Canary coverage.

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/e0d64dc67c6abf36a37efdc6e8e6903bb114ebd3

commit e0d64dc67c6abf36a37efdc6e8e6903bb114ebd3
Author: Ulan Degenbaev <ulan@chromium.org>
Date: Fri Oct 06 11:16:21 2017

[heap] Print the number of chunks in unmapper queue in --trace-gc-nvp

Bug:  chromium:771966 
Change-Id: I146b279c4713b7dd716c6d55ca5e6c6e23a3ad7e
Reviewed-on: https://chromium-review.googlesource.com/704740
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48338}
[modify] https://crrev.com/e0d64dc67c6abf36a37efdc6e8e6903bb114ebd3/src/heap/gc-tracer.cc
[modify] https://crrev.com/e0d64dc67c6abf36a37efdc6e8e6903bb114ebd3/src/heap/spaces.cc
[modify] https://crrev.com/e0d64dc67c6abf36a37efdc6e8e6903bb114ebd3/src/heap/spaces.h

ulan@: does this have enough canary coverage to be merged back?

There is enough coverage. Requesting merges to M60, M61, 62.

Michael, could you please review the merge request?

This bug requires manual review: Request affecting a post-stable build
Please contact the milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), bhthompson@(ChromeOS), abdulsyed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Please add appropriate OSs.

candrada@, the issue affects all OSs.

ulan@: do you expect this issue affect V8 5.1? That is, I am trying to figure out if we need to manually back port for Node 6.x on the Node side.

From Node 8.x+ point of view, we only need the back port to 6.1 and 6.2 (V8 6.0 is no longer relevant to Node.js).

5.1 is not affected.

ulan@ can you please specifically mark all impacted OS's? This will help with our reporting and ensuring the right owner can view it. I know you've mentioned it impacts all OS's, but please mark it in the bug as well. 

Can you please comment why this is urgent and critical for M62? M62 is already in stable rollout for Desktop, Android, and IOS, so the requirements are a bit stricter for merges. go/chrome-merges for more details. 

61 is already deprecated.

Node can float this one and it is a Pri=3. Let's not merge it.

I am suspecting that this is also causing
  https://github.com/nodejs/help/issues/917

Back port for Node: https://github.com/nodejs/node/pull/16490

mlippautz@ is working on decoupling the new generation sweeping from the old generation sweeping.

Just realized that this bug was also used for tracking backmerges. I will open a new one for the improved feature.