<div dir="ltr"><span class="gmail-message"><span class="gmail-content">I've been looking into loading tabbrowser.js lazily: <a href="https://hg.mozilla.org/try/rev/c37940bde57bd278cdf056509cbe54d504e40987" class="gmail-link" rel="noreferrer" target="_blank">https://hg.mozilla.org/try/rev/c37940bde57bd278cdf056509cbe54d504e40987</a></span></span><div id="e127529_1542720892403979" class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent"><span class="gmail-message"><span class="gmail-content"><br></span></span></div><div class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent"><span class="gmail-message"><span class="gmail-content">This seems to help tpaint as one would hope, but hurts pageload tests:</span></span></div><div class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent"><span class="gmail-message"><span class="gmail-content"><span class="gmail-g"></span><span class="gmail-message"><span class="gmail-content"><a href="https://treeherder.mozilla.org/perf.html#/compare?originalProject=try&originalRevision=6c0ba4b678147565bbb58d813e840bfb28703358&newProject=try&newRevision=c37940bde57bd278cdf056509c&framework=1&showOnlyImportant=1" class="gmail-link" rel="noreferrer" target="_blank">https://treeherder.mozilla.org/perf.html#/compare?originalProject=try&originalRevision=6c0ba4b678147565bbb58de813e840bfb28703358&newProject=try&newRevision=c37940bde57bd278cdf056509c&framework=1&showOnlyImportant=1</a><br></span></span></span></span></div><div class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent"><br><span class="gmail-message"><span class="gmail-content"><span class="gmail-message"><span class="gmail-content"></span></span></span></span></div><div class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent"><span class="gmail-message"><span class="gmail-content">I suspect this is a side effect from how pageload tests operate: they're in the startup path and start loading pages quicker than a user would normally be able to. While this is an interesting benchmark, it's probably not the right thing to optimize for between tpaint and loading pages when the browser is already up. How do people feel about accepting this kind of regression, and more generally <span class="gmail-message"><span class="gmail-content">taking startup out of the pageload benchmarks?</span></span></span></span></div><div class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent"><span class="gmail-message"><span class="gmail-content"></span></span><span class="gmail-date"><span class="gmail-timestamp" title="Tuesday, November 20, 2018 14:34:53"></span></span><span class="gmail-g"><br></span></div><div class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent">Side note: Talos reports the tpaint improvement only on Mac. This is because the early blank paint kind of <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1456270">broke tpaint</a> earlier this year on Windows and Linux, so now we can miss improvements *as well as regressions* if for some reason they're less pronounced on Mac. I only remembered this now again, trying to make sense of the talos results. IMHO this is a pretty serious problem that requires some immediate action. We still have telemetry but it doesn't provide the same immediate feedback that we expect from talos.</div><div class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent"><br></div><div class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent">Cheers,</div><div class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent">Dao<br></div><div class="gmail-row gmail-messageRow gmail-sameAuthor gmail-chat gmail-self gmail-type_buffer_msg gmail-userParent"><span class="gmail-g"> </span><span class="gmail-message"><span class="gmail-content"></span></span></div></div>