Author Topic: Avast cuts FIOS download speed in half  (Read 2495 times)

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Offline glnz

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Avast cuts FIOS download speed in half
« on: May 01, 2018, 05:39:09 PM »
 
Just got Verizon 1Gbps Fios on April 12.

After initial wonderful results on www.speedtest.net (regularly 2ms ping, 900± down and 920± up), I noticed that download speed was sometimes much lower - between 400 and 550 Mbps, which is half of what is expected.  Upload speed stayed high.

Now I know it's Avast.  When download speed was lower the other day, Verizon's own speed test said that the router's speed was good in the 900s but my "device" had an issue.  (The "device" is my Win 7 Pro 64-bit PC, on which I'm typing now.)

That was a surprise, and then I remembered that Avast had been the culprit a few times in the past when things went funny.

Sure enough!  When I temporarily disable Avast's shields, the download speed goes right back up to 800-900 Mbps.  When I re-enable the shields, the download speed is cut in half.  I also see in Task Manager that AvastSvc.exe *32 goes like crazy and uses up close to 100% of the CPU during the download.

Now, this is not the end of the world, since even 400 Mpbs download is 50 times faster than my old DSL, but it is ANNOYING.

Hey, Avast, what's the problem?  Can't keep up with the world?  Please fix.

Thanks.
 
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Offline Pondus

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Re: Avast cuts FIOS download speed in half
« Reply #1 on: May 01, 2018, 05:58:58 PM »
Does avast really affect your speed, or is it just messing with the speed test ?

To find out, download a biiiiiig file and take the time, then turn off shields and repeat

is there a minor or big time difference ?

« Last Edit: May 01, 2018, 10:06:58 PM by Pondus »
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Offline DavidR

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Re: Avast cuts FIOS download speed in half
« Reply #2 on: May 01, 2018, 06:53:47 PM »
I'm sure there used to be a setting in the Web Shield that could stop stream (smart) scanning of partial downloads, not to start scanning until the file has fully downloaded.

I believe that was suggested when your download speed was in excess of 300Mbps.  Unfortunately I can't find any such setting now in the web shield.
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Offline glnz

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Re: Avast cuts FIOS download speed in half
« Reply #3 on: May 01, 2018, 07:44:57 PM »
 
David R - can you shoot a message to Avast and ask them about this?

Thanks.
 
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Offline DavidR

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Re: Avast cuts FIOS download speed in half
« Reply #4 on: May 01, 2018, 09:21:38 PM »
I'm not on the developers channel and I'm not so sure the report to moderator will have a great impact, but I will report it.  I don't know why they removed that option, perhaps they thought they had overcome earlier issues with fast broadband.
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Offline Asyn

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Offline DavidR

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Re: Avast cuts FIOS download speed in half
« Reply #6 on: May 02, 2018, 10:18:25 AM »
Hi, see: https://support.avast.com/article/Troubleshoot-Antivirus-Web-Shield

Unfortunately that troubleshooting page is out of date and doesn't reflect the current version for all OSes.  The 'Use intelligent stream scanning' option in the Web Shield Main Settings, doesn't appear to be available on all OS versions, certainly not on my XP installation.  But it is on my win10 laptop.

Since 'glnz' is also running XP, that option isn't available to him either.
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Offline Asyn

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Re: Avast cuts FIOS download speed in half
« Reply #7 on: May 02, 2018, 10:22:12 AM »
Since 'glnz' is also running XP, that option isn't available to him either.
Hi Dave, according to his initial post, he's on Win 7 Pro 64-bit.
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Offline DavidR

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Re: Avast cuts FIOS download speed in half
« Reply #8 on: May 02, 2018, 10:33:32 AM »
Since 'glnz' is also running XP, that option isn't available to him either.
Hi Dave, according to his initial post, he's on Win 7 Pro 64-bit.

Ah I briefly looked at his signature and saw XP and stopped looking.  However, my first reply did suggest unchecking the Stream Scanning in the Web Shield Settings. 

The troubleshooting page is out of date and needs updating as it doesn't reflect the current version for all OSes.  I don't know why this isn't available in XP (it certainly used to be).  I can only assume (dangerous) that Avast on XP no longer uses intelligent stream scanning.  Why this is the case I don't know when it was before and must have worked.
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Offline glnz

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Re: Avast cuts FIOS download speed in half
« Reply #9 on: May 02, 2018, 01:35:32 PM »
 
Asyn and DavidR - Thanks for your attention.

The slowdown is intermittent.  Right now, download on my 7 machine stays just above 800 Mbps whether or not I enable Use Intelligent Screen Scanning.  The slowdowns usually start mid-day.  I'll try again later.

But what is the risk in turning off Use Intelligent Screen Scanning?
 
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Offline DavidR

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Re: Avast cuts FIOS download speed in half
« Reply #10 on: May 02, 2018, 03:12:36 PM »
I would say it is negligible, the intelligent stream scanning is scanning packets as they are downloaded into a temp file, rather than wait for the whole file to be downloaded.

I think this use of the intelligent stream scanning is of more benefit for those who don't have particularly fast broadband, so they don't have to have wait for it to complete to be scanned.

The actual file is likely to be scanned by more than just one shield depending on its file type, the file shield, behaviour shield, hardened mode possibly.  But for general browsing I believe the completed web page and its content and external 3rd party links should be scanned by the web shield.

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Offline glnz

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Re: Avast cuts FIOS download speed in half
« Reply #11 on: May 02, 2018, 03:21:46 PM »
 
DavidR - Thanks.

Of course, the big download in speedtest.net does not result in a web page.  Speedtest.net counts the bits as they rush in and shows the speed.  I suppose the big test download is just dumped.  (Hope so!)

Shall try later today and let you know.
 
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Offline DavidR

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Re: Avast cuts FIOS download speed in half
« Reply #12 on: May 02, 2018, 04:16:13 PM »
I have never specifically checked to see what happens to the downloaded file used for testing purposes. 

But the way I have my systems set up all downloads are saved to a specific folder and Drive, D:\Downloads I never allow it to go to the windows default location (I keep it off the C:\ drive.
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Offline glnz

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Re: Avast cuts FIOS download speed in half
« Reply #13 on: May 02, 2018, 05:10:50 PM »
 
Asyn and David R -

Sorry, but just now UNchecking Use Intelligent Screen Scanning did not help
Before (with Use Intelligent Screen Scanning still enabled) my download was 418.20 Mbps, and
after UNchecking it was 445.81 Mbps, virtually the same and much slower than earlier this morning.

THEN, HOWEVER, after REchecking Use Intelligent Screen Scanning but then DISABLING all shields for 10 minutes, the download speed shot up to 842.13 Mbps.

Again, it's not the end of the world to download at over 400 Mbps, but why is Avast slowing it all down?
 
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Offline Pondus

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Re: Avast cuts FIOS download speed in half
« Reply #14 on: May 02, 2018, 05:18:43 PM »
Did you try my suggestion?

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