1434278 - High CPU usage with cross-domain iframe

Status: RESOLVED DUPLICATE of bug 1237454

(Core :: Layout, defect)

Description

[cjd]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36

Steps to reproduce:

Visit https://cryptpad.fr/pad/#/1/edit/MYUor+IKQ-F6wgMHoqvy5Q/FwSxRsHCgTdaUfJ8PGIIUI7r/
Wait until page is completely loaded
Open performance tab in dev tools, begin recording
Switch to debugger and pause javascript to remove possibility of errent javascript code as cause
Return to performance tab and observe continued CPU usage (seems to concentrate on "JIT")


Actual results:

high (nearly 100%) CPU usage


Expected results:

Normal CPU usage, close to what is observed with Google Chrome and with older FF (I think version 57)

Comment 1

[cjd]

CryptPad has a significant amount (8MB-ish) of CSS so if CSS is being parsed many times, this could be a problem
Older firefox (I think 57) did not have this issue
Chrome does not have this issue
CryptPad uses an iframe containing all of the UI and this is hosted on a different domain in order to protect security of cookies and localStorage from possible XSS attack, I have a strong suspicion that this is the cause - hence the title

Comment 2

[Alice0775 White]

I think this seems to be caused by css animation of hidden elements.

.fa-spin {
    -webkit-animation: fa-spin 2s infinite linear;
    animation: fa-spin 2s infinite linear;
}

Comment 3

[Hiroyuki Ikezoe (:hiro)]

Yes, that's right.  The animation is running on a visibility:hidden element.