Suggesting to enable paint timing by default

# Noam Rosenthal (16 days ago)

Following the discussion with Simon in bugs.webkit.org/show_bug.cgi?id=78011

Since we have a pretty stable spec (w3c.github.io/paint-timing), lots of passing web platform tests, other browser vendor support and a working implementation of first contentful paint, I am planning to submit a patch to enable paint timing by default.

bugs.webkit.org/show_bug.cgi?id=211736

Any objections? Other thoughts?

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# Maciej Stachowiak (16 days ago)

I noticed from comments in one of the Radars that the patch may result in an additional “fake paint”, so it should probably be performance tested. Have you done any testing? We’ll likely want to A/B some of Apple’s page load speed benchmarks.

I’d like to hear from others on maturity of the spec and readiness of the code.

# Noam Rosenthal (15 days ago)

On Tue, May 12, 2020 at 1:36 AM Maciej Stachowiak <mjs at apple.com> wrote:

I noticed from comments in one of the Radars that the patch may result in an additional “fake paint”, so it should probably be performance tested. Have you done any testing?

I've tested it locally, I haven't noticed any significant side effect, because in complex situations the fake paint only happens once per page and bails early once contentfulness is detected. but I can run any additional test needed.

We’ll likely want to A/B some of Apple’s page load speed benchmarks.

A/B testing load speed sounds sensible. How do we go about doing that?

# Maciej Stachowiak (15 days ago)

On May 11, 2020, at 9:53 PM, Noam Rosenthal <noam at webkit.org> wrote:

On Tue, May 12, 2020 at 1:36 AM Maciej Stachowiak <mjs at apple.com <mailto:mjs at apple.com>> wrote:

I noticed from comments in one of the Radars that the patch may result in an additional “fake paint”, so it should probably be performance tested. Have you done any testing? I've tested it locally, I haven't noticed any significant side effect, because in complex situations the fake paint only happens once per page and bails early once contentfulness is detected. but I can run any additional test needed.

We’ll likely want to A/B some of Apple’s page load speed benchmarks. A/B testing load speed sounds sensible. How do we go about doing that?

Unfortunately our page load speed benchmarks are not public because they incorporate captured page content, which we can’t freely redistribute.

A helpful person from Apple may be able to set up an A/B test for this patch.

# Noam Rosenthal (15 days ago)

On Tue, May 12, 2020 at 10:28 AM Maciej Stachowiak <mjs at apple.com> wrote:

On May 11, 2020, at 9:53 PM, Noam Rosenthal <noam at webkit.org> wrote:

On Tue, May 12, 2020 at 1:36 AM Maciej Stachowiak <mjs at apple.com> wrote:

>

I noticed from comments in one of the Radars that the patch may result in an additional “fake paint”, so it should probably be performance tested. Have you done any testing?

I've tested it locally, I haven't noticed any significant side effect, because in complex situations the fake paint only happens once per page and bails early once contentfulness is detected. but I can run any additional test needed.

We’ll likely want to A/B some of Apple’s page load speed benchmarks.

A/B testing load speed sounds sensible. How do we go about doing that?

Unfortunately our page load speed benchmarks are not public because they incorporate captured page content, which we can’t freely redistribute.

A helpful person from Apple may be able to set up an A/B test for this patch.

Understood. I'd be happy to facilitate/support/do what's necessary to move this forward.

# Noam Rosenthal (5 hours ago)

Following up on this.

FOn Tue, May 12, 2020 at 10:28 AM Maciej Stachowiak <mjs at apple.com> wrote:

> >

On May 11, 2020, at 9:53 PM, Noam Rosenthal <noam at webkit.org> wrote:

On Tue, May 12, 2020 at 1:36 AM Maciej Stachowiak <mjs at apple.com> wrote:

>

I noticed from comments in one of the Radars that the patch may result in an additional “fake paint”, so it should probably be performance tested. Have you done any testing?

I've tested it locally, I haven't noticed any significant side effect, because in complex situations the fake paint only happens once per page and bails early once contentfulness is detected. but I can run any additional test needed.

We’ll likely want to A/B some of Apple’s page load speed benchmarks.

A/B testing load speed sounds sensible. How do we go about doing that?

Unfortunately our page load speed benchmarks are not public because they incorporate captured page content, which we can’t freely redistribute.

So, can someone else from Apple review that the code is mature enough for

this? Simon had reviewed the original patch. Maybe Zalan/Darin?

A helpful person from Apple may be able to set up an A/B test for this

# Yoav Weiss (4 hours ago)

+Ryosuke Niwa <rniwa at webkit.org> +Alex Christensen <achristensen at apple.com> who

were involved in the spec discussions.

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