Author Topic: Rather odd scan problem  (Read 2844 times)

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Offline Uh_Clem

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Rather odd scan problem
« on: November 10, 2011, 07:21:07 AM »
This is a problem I reported with beta 30664 on the support site but they have since advised me to post beta issues to the forum.  Since it is still a problem with release 35600, I'm resubmitting it.  This is, admittedly, something of an esoteric issue but it puzzles me that it should happen at all.  Herewith the text of my original report:

**************************
I have a puzzling problem with some of my scans using avast! beta 1.0 (30664). For a full system or custom scan that includes a particular path and file, the scan hangs for a considerable amount of time while using much of the CPU to accomplish very little.

On the primary drive of my MacBook Pro running OS X 10.6, there is a 4.3 MB JPEG file in the following path:

HD 1/Users/username/Desktop/hold photos/ULV_Mustard.jpg

I won't go into the details of the file since, as I shall describe later, they do not seem to be the significant factors. What should be noted is that the file is the last (alphabetically) file in its folder which is the last folder -- but not the last file -- in the Desktop folder.

I can successfully scan the file, by itself, in about 1 second (as stated in the avast! 'Scan duration'). The folder which contains it scans in 10 seconds. However, if I scan at any higher level in the hierarchy (Desktop, username, Users, HD 1 or Full System), the scan progresses until it reaches this file then it appears to just hang. The Activity Monitor shows that the avast process com.avast.MacAvast.MAD.orig is using in excess of 70% of the CPU. After approximately 10 minutes, the scan proceeds through the remaining files to completion.

In experimenting, I removed the offending file and repeated the scan. This time, the scan hangs at the immediately preceding file (which is now the last file in the folder). I then created another folder 'hold photos copy' and copied a file into it. 'hold photos copy' is now the last folder in the Desktop folder and, indeed, the scan successfully completes the files in 'hold photos' but hangs on the one file in 'hold photos copy'. I removed the JPEG file from that newer folder leaving it apparently empty but the next test scan hung on the invisible (and miniscule) .ds_store in that folder.

In all cases the scan hangs for 10 minutes, making me wonder if there is some sort of timeout built into the avast engine.

The preference options selected are as follows:

Shields - all shields enabled
Popups - duration '15 secs', verbosity 'all messages', position 'right top corner'
On-demand scans - Scan whole files, include warnings about files which cannot be scanned
Miscellaneous - show avast! icon in menu bar

The problem goes away if I uncheck 'Scan whole files' but I am at a loss as to why the file or its folder scan in 10 seconds or less by themselves even with the option checked.

**************************
Just as an added note, the files have changed from when I first submitted this but the problem remains the same -- with 'Scan whole files' checked, the scan hangs on the last file of the last folder in the Desktop directory.

Offline zilog

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Re: Rather odd scan problem
« Reply #1 on: November 10, 2011, 10:55:59 AM »
This is a problem I reported with beta 30664 on the support site but they have since advised me to post beta issues to the forum.  Since it is still a problem with release 35600, I'm resubmitting it.  This is, admittedly, something of an esoteric issue but it puzzles me that it should happen at all.  Herewith the text of my original report:

**************************
I have a puzzling problem with some of my scans using avast! beta 1.0 (30664). For a full system or custom scan that includes a particular path and file, the scan hangs for a considerable amount of time while using much of the CPU to accomplish very little.

On the primary drive of my MacBook Pro running OS X 10.6, there is a 4.3 MB JPEG file in the following path:

HD 1/Users/username/Desktop/hold photos/ULV_Mustard.jpg

I won't go into the details of the file since, as I shall describe later, they do not seem to be the significant factors. What should be noted is that the file is the last (alphabetically) file in its folder which is the last folder -- but not the last file -- in the Desktop folder.

I can successfully scan the file, by itself, in about 1 second (as stated in the avast! 'Scan duration'). The folder which contains it scans in 10 seconds. However, if I scan at any higher level in the hierarchy (Desktop, username, Users, HD 1 or Full System), the scan progresses until it reaches this file then it appears to just hang. The Activity Monitor shows that the avast process com.avast.MacAvast.MAD.orig is using in excess of 70% of the CPU. After approximately 10 minutes, the scan proceeds through the remaining files to completion.

In experimenting, I removed the offending file and repeated the scan. This time, the scan hangs at the immediately preceding file (which is now the last file in the folder). I then created another folder 'hold photos copy' and copied a file into it. 'hold photos copy' is now the last folder in the Desktop folder and, indeed, the scan successfully completes the files in 'hold photos' but hangs on the one file in 'hold photos copy'. I removed the JPEG file from that newer folder leaving it apparently empty but the next test scan hung on the invisible (and miniscule) .ds_store in that folder.

In all cases the scan hangs for 10 minutes, making me wonder if there is some sort of timeout built into the avast engine.

The preference options selected are as follows:

Shields - all shields enabled
Popups - duration '15 secs', verbosity 'all messages', position 'right top corner'
On-demand scans - Scan whole files, include warnings about files which cannot be scanned
Miscellaneous - show avast! icon in menu bar

The problem goes away if I uncheck 'Scan whole files' but I am at a loss as to why the file or its folder scan in 10 seconds or less by themselves even with the option checked.

**************************
Just as an added note, the files have changed from when I first submitted this but the problem remains the same -- with 'Scan whole files' checked, the scan hangs on the last file of the last folder in the Desktop directory.


Hallo,
very last item in the directory is, on MacOS X , also the very last item in alphabetical order (yes, direntries are always sorted there).

So, maybe, the culprit might be the very next file which wouild be scanned after. Pleae, turn on full loging (loggin also OK files), do the contended scan with the hang-effect, and have a look at the items around the sticking point. This will give you maybe a clude about the real cause.

regards,
pc
May's Law: Software efficiency halves every 18 months, compensating Moore's Law. (David May, INMOS)

Offline Uh_Clem

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Re: Rather odd scan problem
« Reply #2 on: November 20, 2011, 05:54:53 AM »
Thanks, PC, you nailed it!  I was fixated on the idea that the name displayed was the file currently being scanned.  When I moved the following file from the scan (a rather large .ISO file) the procedure took seconds.

Interestingly, when that file was part of the folder scan, the "interruption" took almost exactly 10 minutes before proceeding to the next files.  When I scan that file individually, the scan takes 17 minutes.

Now on to the next items...