nemo significantly slower opening folder content

[howdev]

 * Nemo version (3.8.5)
 * Is issue with filemanager nemo
 * Distribution - Mint 19
 * Graphics hardware *and* driver (unrelated)
 *  64 bit

Issue
This issue has been reported prior to Mint 18.
Nemo open folders very slow. slower than Nautilus. much slower than Thunar.
We expected the issue to be resolved in Mint 19, but still hasn't

Steps to reproduce
Open nemo filemanager open some folder with contents.
Especially can be test with /usr/bin directory. While Thunar opens instantly, there is a significant delay with nemo. to browse any folder with low item count still can see blank page then folders showing.

Expected behaviour
instant show of folder contents

Other information

[mtwebster]

I can't agree with the nautilus comparison. Testing side-by-side, using the same style view they appear to me nearly the same. Both programs load their list view fairly quickly, and the icon view slowly. One difference is that nautilus uses the list view as its default, whereas nemo uses the icon view. This can be changed in the first tab of preferences.

Additionally, the number and type of extensions in use can vastly affect load times.

Efforts are being constantly made to improve these speeds. We're aware of thunar's performance, but it's not trivial to just say 'do it the way they do it' and snap our fingers.

[howdev]

Although you may not agree with nautilus comparison. many have complained nemo is slower than nautilus. I continuously click on the the sidebar shortcuts they both use about the same CPU load but nemo is slower in refresh visually. Thunar uses the much less CPU.

I made the test in the past, I disabled extensions and made no difference

[donlencho]

Since upgrading to Mint 19 (and now using Nemo 3.8.5), handling files in folders with a large number of files has become practically impossible, it uses one CPU to almost 100% to make any action (moving a file, creating a folder, ...) and can take up to 5-10 seconds to respond.
Not sure this is the behaviour you are referring to, but maybe in part.
I'll also react to #1902.

[howdev]

@donlencho Is not that serious with me where it uses 100% CPU but it does use alot when you browse folders. Not only high CPU load but visually slow. It is terrible to use when you are working on projects where you browse to many levels of subdirectories, I need to wait for folder to appear before clicking on it.

[howdev]

@mtwebster There are certainly many ways of doing things. The disappointment is after several major updates to Linux Mint there is no improvement of nemo's performance, not even to know what the issue is causing the slowness. Perhaps to do with the way gtk3 works.

[brownsr]

@howdev @donlencho Is there any thing you can do to help pin down where the problems you experience are ? So far you have identified 1) folders with a very large number of files 2) folders with many levels of subdirectories. Could you try, for example, a) disabling plugins, actions [edit, plugins] b) turning off thumbnails c) turning off folder counting [edit, preferences] and feed back if any of those make a difference. Similarly clarify what other preferences you might be using, such as tooltips and try changing those modes d) say if you get differences with different types of nemo view e) clarify what types of disk storage you are using, and how full you are running the disks

Regards

Simon

[howdev]

@brownsr The issues is not about many subfolders. The slowness is from loading folder contents whether they are files or folders. It is slow to display even the content only contain few items. Plugins disable tested before no difference.

GTK3 had a similar performance issue in the past with slow appending liststore. Someone suggested to use insert_with_valuesv instead. This may have to do with the way the model is populated for the iconview

And by the way I think this may have to do with sorting of the model as well. The populate and sorting of the model needs to be investigated.

[howdev]

https://stackoverflow.com/questions/3547743/gtktreeview-insert-update-performance-penalty-because-of-sorting

This is another problem I found on is to do with sorting in treeview. The sorting is to do with model and regardless of the view whether is treeview or iconview.

[donlencho]

Not sure we are talking about the same problem, as said before. I'll keep posting in #1902 instead.
The problem for me is not immediate, when the system starts, it's fine (well I'm not talking about a speed contest between file managers, I'm not testing others).

[howdev]

you may say can't compare gtk2 and gtk3 app, but I just installed Thunar 1.8 is gtk3 and still as fast as Thunar gtk2 @mtwebster therefore should investigate the way Thunar does it. There is serious problem the way nemo does the iconview with the model

[andrewufrank]

I have serious difficulties with opening folders which are on a mounted separate disk. Nemo works fast on opening one of two external disk, but not the other. The entries in fstab are:

/dev/mapper/london--vg-additionalSpaceAF /home/frank/additionalSpace ext4 rw,relatime,data=ordered 0 0
/dev/mapper/london--vg-scratchAF /home/frank/Scratch ext4 rw,relatime,stripe=4,data=ordered 0 0

Nemo goes to 100% cpu only on one folder in this second disk. What information could I provide to help tracing this problem? What could be different in this folder from the others?

[NikoKrause]

First I would eliminate any hardware issues, e.g. try different cables. Does it happen with other file managers, e.g. nautilus.

[mtwebster]

Does this folder have a lot of pictures or other file types that have a thumbnail generated?

Try a couple things:

This gets rid of existing thumbnails (in case there's an issue with one that's being hung on)
rm -rf ~/.cache/thumbnails (if you get a permission error, use sudo)

and/or

Try disabling thumbnailing: Preferences->Previews->Show Thumbnails - Never

Ensure you've got a new instance of nemo:

nemo --quit
nemo

Also, you can try disabling any extensions temporarily (Edit->Plugins, lower section) and again, restart.

[andrewufrank]

Thank you for the advice - nothing helps. No thumbnails in the file, not shown anyhow; disabled all extensions (nothing was present beyond the defaults).

Most surprising, if I open the folders from outside by unfolding them in the same windows, no undue delays occur. it is only in this folder for one folder, if it is opened (not unfolded), then nemo goes into 100 % cpu. What could be special about this folder (all others in the same folder open ok)?

[mtwebster]

Open a terminal in that folder, run ls -la - is there anything weird in there? Strange owner, permission bits, recursive links?

The fact it opens ok from the parent folder makes me think there's something wrong maybe inside one of the children of problem folder. Under normal circumstances, a view's 'directory' doesn't delve deeper than one layer deep of children by default (you get 'deep' counts only when doing things like right-click->properties or copy/move operations). Though I'd think no matter how you view the folder, you'd run into the problem (whether expanding from the parent or some other way).

Regardless, check the members of the folder as mentioned, and one deep in any child folders. Does this happen in the icon view also? Also, what version of nemo is this and what distro are you on?