High CPU and memory usage

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Guest1234

High CPU and memory usage

Post by Guest1234 »

Firefox 86.0
NoScript 11.2.3
In a Firefox Private Window go to:
https://www.tesco.com/groceries/?icid=d ... pgroceries
Open Firefox Task Manager.
In NoScript set ...tesco.com to Temp. TRUSTED
In NoScript set ...bing.com to Temp. TRUSTED
Windows Task Manager shows high CPU usage for Firefox and large & increasing memory usage.
Firefox Task Manager shows NoScript has High Energy Impact
Not sure whether this is an issue with Firefox, NoScript or the Tesco web site.
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:86.0) Gecko/20100101 Firefox/86.0
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therube
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Re: High CPU and memory usage

Post by therube »

Did you test with NoScript disabled (or perhaps better, in Safe Mode)?
(I.e., might it be a Tesco/FF issue & not related to NoScript?)
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.19) Gecko/20110420 SeaMonkey/2.0.14 Pinball NoScript FlashGot AdblockPlus
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Giorgio Maone
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Re: High CPU and memory usage

Post by Giorgio Maone »

I can't reproduce.
Maybe a Firefox / Tesco issue (as suggested by therube) or an extensions conflict.
Please try also on a clean profile with just NoScript installed to rule out the latter.
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:87.0) Gecko/20100101 Firefox/87.0
Guest1234

Re: High CPU and memory usage

Post by Guest1234 »

Just done another test:
Opened Windows Task Manager.
Opened Firefox.
Under about:addons I only have 2 Extensions - NoScript and Norton Safe Web.
I disabled both.
In a Firefox Private Window I went to:
https://www.tesco.com/groceries/?icid=d ... pgroceries
Windows Task Manager CPU and memory usage were normal.
I enabled NoScript in about:addons.
Windows Task Manager CPU and memory usage were normal.
In NoScript I set ...tesco.com to Temp. TRUSTED.
Windows Task Manager CPU and memory usage were normal.
Opened Firefox Task Manager - Energy Impact shows as Low.
In NoScript I set ...bing.com to Temp. TRUSTED.
Windows Task Manager shows high CPU usage for Firefox and increasing memory usage.
Firefox Task Manager shows NoScript Add-on has High Energy Impact.

I had hoped the problem would be reproducible.
I will look into how to test with a clean profile - I haven't done it before.
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:86.0) Gecko/20100101 Firefox/86.0
Guest1234

Re: High CPU and memory usage

Post by Guest1234 »

I tried a clean profile with just NoScript.
At first I couldn't reproduce the CPU and memory problem.
I tried changing some settings and after few experiments it looks like the problem occurs if in the NoScript Options, General tab the Default tab has fetch unticked.
I went back to my normal profile and got the same result (it had fetch unticked).
Can you reproduce it now?
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Giorgio Maone
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Re: High CPU and memory usage

Post by Giorgio Maone »

Guest1234 wrote: Fri Feb 26, 2021 8:26 pm I tried a clean profile with just NoScript.
At first I couldn't reproduce the CPU and memory problem.
I tried changing some settings and after few experiments it looks like the problem occurs if in the NoScript Options, General tab the Default tab has fetch unticked.
I went back to my normal profile and got the same result (it had fetch unticked).
Can you reproduce it now?
I can, indeed.
The website desperately tries to fetch resources from 3rd party (DEFAULT) repeatedly failing in a tight loop because NoScript blocks the request, causing both the page and NoScript itself to clog the CPU.

I'm gonna try to create some mitigation for this kind of scenario, even though there's not really much you can do in against self-DOS.

But on the other hand there's a reason why the DEFAULT preset has the "fetch" capability enabled out of the box: in order to use fetch / xhr a website must have the script capability (which is disabled in DEFAULT), and cross-domain fetches are subject to CORS.
Therefore in most scenarios forbidding fetch just prevents data resources from being read by actors which have legitimate rights to do it and for which you've already allowed scripting.
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Re: High CPU and memory usage

Post by Guest »

Pleased to hear that you have been able to reproduce the problem and figure out what is causing it.
FYI - I have been using the Tesco website to order weekly food deliveries to my home since the UK went into a "stay at home" coronavirus lockdown.
It worked fine until today (with DEFAULT fetch unticked) so something must have changed in the last week.
I did wonder if it might be something related to the recent change to Firefox 86.0 but it sounds like Tesco must have changed the way their web site works, and not in a good way! - I hope that there are not many other NoScript users with DEFAULT fetch unticked that shop at Tesco!
I will set DEFAULT fetch to ticked.
Thank you for your help with this problem and for providing NoScript.
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:86.0) Gecko/20100101 Firefox/86.0
RichArnold

Re: High CPU and memory usage

Post by RichArnold »

Just came across this thread as I did a quick search whilst doing my weekly tesco shop....

I have a 9900k running at 5ghz on all cores and use Edge for my explorer.

Every time I search for a product on Tesco, my temps go from 27 degrees to 62.

There's definitely an issue.
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