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Firefox engineers discover a Windows Defender bug that causes high CPU usage

bugzilla.mozilla.org

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Re: Firefox engineers discover a Windows Defender bug that causes high CPU usage

#21

Post by boringuser2 »

marcodiego wrote: post #13

> a ~75% CPU usage reduction was noted when browsing YouTube in Firefox I wonder how many of the people who say "Firefox is significantly slower than chrome" are using windows... On my computer, Firefox IS slower than chrome but (with ad blockers enabled) by an insignificant amount. By still being "the last remaining mostly independent, maintained and reasonably popular browser" I'd prefer it to use over chrome even…

Firefox is significantly slower than chrome.

This usually doesn't matter, but you can immediately see it in any page that

A) has a massive DOM

or

B) uses complex regular expressions that eat up the engine

Re: Firefox engineers discover a Windows Defender bug that causes high CPU usage

#22

Post by muststopmyths »

JoeAltmaier wrote: post #14
consumer451 wrote: post #10

Random thought: I am not sure what the at-scale energy use reduction of this bug fix will be, but... If I had a pile of money I would consider creating a special bug bounty style program for energy use reduction. This might be a very efficient way to reduce carbon output from personal and data center computing.

Funny how that sort of thing can work out. I was involved in an industrial optimization company years ago. Microsoft came out with power-save features in their new release. The staff at a metal-recycling company we were installing at, started complaining that the furnace would stop optimizing overnight. We investigated. The controller computer would go into power-save mode, which suspended our control app. So the fur…

Or… the controller app could be written to prevent suspension via available APIs. If that wasn’t an option, you could turn off power saving mode on the computer as well.

Re: Firefox engineers discover a Windows Defender bug that causes high CPU usage

#23

Post by jandrese »

marcodiego wrote: post #13

> a ~75% CPU usage reduction was noted when browsing YouTube in Firefox I wonder how many of the people who say "Firefox is significantly slower than chrome" are using windows... On my computer, Firefox IS slower than chrome but (with ad blockers enabled) by an insignificant amount. By still being "the last remaining mostly independent, maintained and reasonably popular browser" I'd prefer it to use over chrome even…

I have definitely noticed my laptop fans spinning up whenever I do Youtube on Firefox on Windows. I just figured the GPU acceleration was broken, but this makes sense. Certainly not the first time Windows Defender has consumed extraordinary amounts of system resources for simple tasks.

Re: Firefox engineers discover a Windows Defender bug that causes high CPU usage

#24

Post by JoeAltmaier »

muststopmyths wrote: post #22
JoeAltmaier wrote: post #14

Earlier quoted context omitted.

Funny how that sort of thing can work out. I was involved in an industrial optimization company years ago. Microsoft came out with power-save features in their new release. The staff at a metal-recycling company we were installing at, started complaining that the furnace would stop optimizing overnight. We investigated. The controller computer would go into power-save mode, which suspended our control app. So the fur…

Or… the controller app could be written to prevent suspension via available APIs. If that wasn’t an option, you could turn off power saving mode on the computer as well.

Power save was a new thing. We were all learning.

Re: Firefox engineers discover a Windows Defender bug that causes high CPU usage

#25

Post by ivanmontillam »

I've experienced a bug related to the on-disk real-time scanning of Windows Defender, but instead with 100% disk bandwidth usage for unreasonable amounts of time.

I purchased a license of a proper antivirus software to avoid that bug and the performance issues gone away.

When you install another AV software, Windows Defender steps down and leaves scanning to the 3rd-party security solution. I selected one of the most lightweight ones I could find. It has been a net win for me.

One shouldn't need to do this, but it has worked so far, for years now.

Re: Firefox engineers discover a Windows Defender bug that causes high CPU usage

#26

Post by JoeAltmaier »

paulryanrogers wrote: post #16
JoeAltmaier wrote: post #14

Earlier quoted context omitted.

Funny how that sort of thing can work out. I was involved in an industrial optimization company years ago. Microsoft came out with power-save features in their new release. The staff at a metal-recycling company we were installing at, started complaining that the furnace would stop optimizing overnight. We investigated. The controller computer would go into power-save mode, which suspended our control app. So the fur…

Isn't this more a failing of the operator: using a consumer grade OS for an industrial case?

Such distinctions were not so available back then.

Re: Firefox engineers discover a Windows Defender bug that causes high CPU usage

#27

Post by IronWolve »

mconley wrote: post #4

TL;DR: Windows Defender had a bug that made certain system calls expensive on CPU cycles when Defender's Real-time Protection feature is enabled. After discovery, Mozilla reported this issue to Microsoft. Microsoft is releasing a patch that should result in lower CPU usage when using Firefox on sites like YouTube (a ~75% CPU usage reduction was noted when browsing YouTube in Firefox with the fixed version of Defender…

It's not just mozilla, been working defender issues for the last few years on thousands of windows vm's. Mostly due to the enabling the more intensive heuristic real time engine and they have different code bases depending on versions installed on different windows builds, and patching does seem to trigger it. For months we had issues where we couldnt log into some vm's due to high cpu for defender, and had to bounce the vm and apply a temp defender fix.

I think its a growing issue, as they mature/migrate their older code base, issues become less frequent.

Re: Firefox engineers discover a Windows Defender bug that causes high CPU usage

#28

Post by moonchrome »

This just reminds me of constant "things worked so fast on my Windows 95 machine back in the day with 16MB RAM". Meanwhile any piece of software could crash your PC and it did so regularly (I still keep spamming save in software because of those days) and internet was a pandoras box.

I wonder how much overhead in modern OS/PC user experience comes from security/stability abstractions and tools.

Re: Firefox engineers discover a Windows Defender bug that causes high CPU usage

#29

Post by Arrath »

ivanmontillam wrote: post #25

I've experienced a bug related to the on-disk real-time scanning of Windows Defender, but instead with 100% disk bandwidth usage for unreasonable amounts of time. I purchased a license of a proper antivirus software to avoid that bug and the performance issues gone away. When you install another AV software, Windows Defender steps down and leaves scanning to the 3rd-party security solution. I selected one of the most…

> I've experienced a bug related to the on-disk real-time scanning of Windows Defender, but instead with 100% disk bandwidth usage for unreasonable amounts of time.

Sophos does this on my work laptop with depressing regularity. At this point I just go grab coffee when the fans max out, cause I know the disk is similarly pegged and it'll be about as snappy as a bogged down Windows 98 machine until it finishes.

Re: Firefox engineers discover a Windows Defender bug that causes high CPU usage

#30

Post by solarkraft »

marcodiego wrote: post #13

> a ~75% CPU usage reduction was noted when browsing YouTube in Firefox I wonder how many of the people who say "Firefox is significantly slower than chrome" are using windows... On my computer, Firefox IS slower than chrome but (with ad blockers enabled) by an insignificant amount. By still being "the last remaining mostly independent, maintained and reasonably popular browser" I'd prefer it to use over chrome even…

It's much much slower for me on macOS. But that's with all my extensions while I don't have as many on Chrome.
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