https://bugs.kde.org/show_bug.cgi?id=503364
Bug ID: 503364
Summary: K7Zip Appears to Extract the Whole Archive When
Calling KArchive::open
Classification: Frameworks and Libraries
Product: frameworks-karchive
Version: 6.13.0
Platform: Other
OS: Linux
Status: REPORTED
Severity: major
Priority: NOR
Component: general
Assignee: kio-bugs-n...@kde.org
Reporter: bryantc...@gmail.com
CC: kdelibs-b...@kde.org
Target Milestone: ---
SUMMARY
KArchive takes a long time to open 7z archives compared to other software.
Opening a 7z archive and getting the entry list in Ark is essentially instant.
Noticed the time it took for KArchive to open the same 7z archive seemed to be
about the same as it would take for Ark to extract that archive. Looking at
memory usage when my software was opening said archives I noticed the memory
usage was much higher than when opening other archives. It would spike up
initially when opening by several times the size of the archive then drop down.
Even after it was opened it is still using much more memory for the instance of
the K7Zip compared to other archives. Just having it open appears to have about
as much memory in use by it as the entire archive. Which makes me think that
K7Zip is extracting the whole archive to memory when calling KArchive::open.
STEPS TO REPRODUCE
For repro steps I will give two options since the behavior can be seen with any
program utilizing KArchive for 7z support. Also will mention the archive in
question I was using for testing was a folder with 200 jpgs in it at around
150MB in total size.
Option 1: Okular
1. Using Okular open a .cb7 archive compressed with either LZMA, LZMA2, or
BZip2. BZip2 is recommended since it will take the longest so will be most
noticeable. Any of them are fine though.
2. Check the memory it is using
3. Now make a cbz of the contents of that archive and look at the difference in
memory usage when opening it in Okular
Option 2: Create a small snippet of code
1. Create a small snippet of code that simply opens an archive and gets the
entry list. With debug messages between the steps.
OBSERVED RESULT
For Okular you will notice that it takes significantly longer to open a a cb7
archive compared to cbz while using more memory.
For the snippet of code you will notice it hanging on the open.
EXPECTED RESULT
For it to open in a timely manner and not have essentially the whole archive
loaded into RAM.
SOFTWARE/OS VERSIONS
Linux: 6.14.2
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.13.0
Qt Version: 6.8.2
ADDITIONAL INFORMATION
This behavior dates quite far back I have a Pop!_OS 20.04 system I still use
for some things which also experiences the exact same issue with a long time to
open and high memory usage with K7Zip. So this issue appears to have been
around for at least 5 years it seems.
Hope my explanation of the bug/issue is good enough it might be a little
confusing with the wording opening. Some may think I am referring to extracting
it or something, but I am just referring to creating an IODevice essentially
and just reading the entry list which shouldn't take any real amount of time
with modern processors I believe. Certainly shouldn't if Ark and other archive
tools which don't rely on KArchive can show the entry list near instantly.
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