1438829 - Avast/AVG slowing down JS

Status: RESOLVED WORKSFORME

(External Software Affecting Firefox :: Other, enhancement, P3)

Description

[Marco Castelluccio [:marco]]

We have received several reports of performance regressions with Firefox. Many of the reporters have Avast installed.

One of the reporters managed to get a profile, which shows the content process being blocked for two seconds in awsJsFlt.dll: https://perfht.ml/2EtTcUk.

https://support.mozilla.org/en-US/questions/1205526
https://www.camp-firefox.de/forum/viewtopic.php?f=1&t=124379
https://www.reddit.com/r/firefox/comments/7xm68n/5802_update_slowbuggy_for_anyone_else/

Comment 1

[[:philipp]]

the same issue also seems to happen with AVG branded products as well (same company). 2 more profiles:
# https://perfht.ml/2o5Broi from https://support.mozilla.org/en-US/questions/1205672
# https://perfht.ml/2oc8R3W from https://www.reddit.com/r/firefox/comments/7xsw2y/why_so_laggy/duble7s/

Comment 2

[[:philipp]]

using multiple firefox profiles was mentioned in various support threads, so this may be a factor playing into the issue as well.

Comment 3

[Lukas Rypacek]

H folks, the Avast Viruslab team has found a potential problem in the code that synchronizes Javascript scanner with the main AV service. We have prepared a fix which is scheduled for release as a part of a regular virus DB update on Monday 19/2/2018. Similar fix will be released for AVG brand.

Comment 4

[aafn]

Problem still here today, Feb 21st, and I confirm, I just uninstalled Avast Antivirus, and the slowness disappeared.

Slowness was quite significant, I have developped an add-on where I am tracing some processing time when I need to debug, both on FF native primitives and on my code, and I could observe an performance decrease by a factor of 5 to 6 !!

For example:
- a browser.bookmarks.getTree() on my 1800 or so bookmarks is now taking again 200 ms after uninstall, as it was before the slowness appeared, and it was taking around 1000 ms with Avast installed.
- display of my 1800 bookmarks is now back to around 500 ms, while with Avast installed, it was around 3000 ms !!

My virus definitions just before I uninstalled were from today, Feb. 21st. So I had the latest.
I have only one FF profile.

Avast is definitely doing something wrong !!
I will try to reinstall to see if the problem reappears .. If so, I will uninstall Avast until somebody tells here this is resolved.

Comment 5

[Vaclav Pich]

Dear aafn,
to identify the source of firefox slow down and prepare a fix, 
I would like to ask you to perform your measurement once again with xperf tool and share with us xperf logs :

1) Download xperf tools from msdn ( https://docs.microsoft.com/en-us/windows-hardware/test/wpt/ )

2) Prepare your test case - without avast
3) Start xperf tool with command : xperf.exe -on DiagEasy+DISPATCHER+Profile -stackwalk profile+CSwitch+ReadyThread -start avast -f \avast.etl -on 1492D477-3272-5C0C-D91A-C156CC3CD206 -start inet -f \inet.etl -on Microsoft-Windows-WinINet
4) Run your tests
4) Collect xperf logs with command: xperf.exe" -stop -stop avast -stop inet -d xperf_log_merged.etl


Repeat the same steps also with avast installed. 

Thank you in advance for your help and report !

Best regards,
Vaclav Pich

Comment 6

[aafn]

Hello Vaclav Pich,

thank you much for your support. Problem solved and this was not Avast after all.

For a reason I have yet to investigate, my power management settings were modified at the time of latest Windows update last week, and were in a mode where cpu was throttled some time after boot. Therefore, when testing after Avast uninstall, since that was just after boot, all was fine, making me erroneously conclude that the performance decrease/increase was linked with Avast presence or not, sorry for that.

That will teach me to better pay attention that testing conditions are identical before concluding ..! My apologies again then for that erroneous problem determination, all is fine, with Avast reinstalled now.

Comment 7

[Vaclav Pich]

Dear aafn,
it is nice to hear that avast didnt cause the slowdown!
Your description looked differenty than original issue reposted by Marco Castelluccio. 
We released a fix for the original issue a week ago.
Best regards,
Vaclav Pich

Comment 8

[Marco Castelluccio [:marco]]

Thanks for the fix!

Could you share some details on what happened?
Is there anything we can do on our side to prevent this from happening in the future?

Comment 9

[Vaclav Pich]

Remonator in (https://support.mozilla.org/en-US/questions/1205526 ) mentioned that avast update required reboot to finish, after reboot everything went back to normal - no issues observed so fix turns off a part of script scanning service till update finish.
Best regards,
Vaclav Pich