[kde] [Bug 467561] New: Nfs /home client hopeless since linux kernel 6.2

[Richard PALO]

https://bugs.kde.org/show_bug.cgi?id=467561

            Bug ID: 467561
           Summary: Nfs /home client hopeless since linux kernel 6.2
    Classification: I don't know
           Product: kde
           Version: unspecified
          Platform: Archlinux
                OS: Linux
            Status: REPORTED
          Severity: grave
          Priority: NOR
         Component: general
          Assignee: unassigned-bugs at kde.org
          Reporter: richard.palo at free.fr
  Target Milestone: ---

Created attachment 157411
  --> https://bugs.kde.org/attachment.cgi?id=157411&action=edit
inxi -FAZ output on LTS

SUMMARY
I report here as it is unclear which particular component is responsible...
I've tried to solicit info via the KDE and EndeavourOS fora:
- https://forum.kde.org/viewtopic.php?f=18&t=177449
-
https://forum.endeavouros.com/t/nfs-home-client-hopeless-since-linux-kernel-6-2/38098
(given the distro EndeavourOS is Arch based, but isn't listed I indicated
Archlinux above)

Primary info reproduced here:
================================
Been running nfs /home on our Arch based clients since years, and more recently
having upgraded the HW to Asus PN51-E1s, we moved to EndeavourOS… But since a
week it is impossible to run mainstream, luckily linux-lts is unaffected.

Currently running KDE/plasma

Operating System: EndeavourOS 
KDE Plasma Version: 5.27.2
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8
Kernel Version: 6.1.15-1-lts or 6.2.2-arch1-1 (64-bit)
Graphics Platform: X11
Processors: 12 × AMD Ryzen 5 5500U with Radeon Graphics
Memory: 30.7 Gio of RAM
Graphics Processor: AMD Radeon Graphics
Manufacturer: ASUSTeK COMPUTER INC.
Product Name: MINIPC PN51-E1
System Version: 0505

Resulting mount (from /etc/fstab) is thus
server:/home/richard on /home/richard type nfs4
(rw,relatime,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=14,retrans=2,sec=sys,clientaddr=192.168.0.41,local_lock=none,addr=192.168.0.1)

/etc/fstab uses
https://wiki.archlinux.org/title/NFS#Mount_using_/etc/fstab_with_systemd 1
plus in /etc/nfsmount.conf

[ MountPoint "/export/home" ]
background=True

The server is pure arch x86_64 running 6.1.15-1-lts on a supermicro H8SGL-F

What are the symptoms?

Extremely long login times, on LTS it’s nearly interactive (<5seconds) vs a
minute or two
using dolphin accessing /home or other nfs shares is excruciating, mostly on
first access (also long moments as opposed to nearly interactive) and file
accesses are clearly longer, though maybe not as exaggerated as folder
openings.

Booting back and forth between LTS and mainstream reproduces the problem.

It seems like perhaps a serious caching problem, or worse.

==================

ADDITIONAL INFORMATION
Not having too much time to spend on this as running LTS doesn’t exhibit the
problem, this morning I believe I can determine that it’s possible that QT is
at fault.
That is, with plasma there is dolphin, by default, which has the problem. So I
installed pcmanfm and pcmanfm-qt to see about alternatives because in a
terminal screen access on NFS seems just fine.

pcmanfm on both lts and mainstream seems just fine
pcmanfm-qt is similar to dolphin, fine on lts but dog slow on mainstream.

Anybody else can verify that? or knows of any way to tune? perhaps it needs a
larger read_ahead_kb or something.

[added] and maybe it’s me, but it seems that in lts, dolphin loads fast, then
asynchronously adds the size of folders later, a bit at a time… in mainstream
it looks perhaps synchronous, evidently taking a real long time to interrogate
the nfs server for all that… possible difference in the semantics of the
underlying calls?

BTW, currently linux 6.2.6.arch1-1 is installed and exhibits the same problem
(QT5 5.15.8+kde+r183-1)
and LTS is at 6.1.19-1-lts.

We also have numerous other NFS mounts from the same server which exhibits the
same symptoms as $HOME

Ultimately, KDE on our platforms is unusable on Linux 6.2, if no resolution is
found before LTS upgrades to 6.2 or higher with similar results, we'll have to
roll back to LXDE as our desktop platform.

for completeness, I attach the output from `inxi -Faz`  from LTS.

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