On 12/12/2019 06:33, Terry Barnaby wrote:
I have just started to try out Fedora31 on some of our systems.
I am using a bit of an unusual, manual install method copying an image
of the rootfs to the disk and configuring this, (this may be related
to my issue, but I have been using the same system for 6 years or
more). The particular hardware platform is a bit complicated using a
PCIe card with NVMe disk and two SATA disks. It has to boot (BIOS boot
and /boot) from one of the SATA disks and then uses the rootfs system
on the NVMe disk. I don't think that is related to the the issue though.
The issue is that when I run "grub2-mkconfig -o /boot/grub2/grub.cfg"
to manually configure grub2, this process hangs. There is a process
grub2-mount that is sitting there using 100% of a CPU core. Not sure
what this process does (seems new after Fedora29) but it is passed the
/dev entry for a disk partition some presumably mounts the file system
and "probes" for what OS is installed there. The file system it hangs
on (if you kill the grub2-mount process it will hang on another
drive), is easily mountable without any issues.
It seems like there is some bug in this grub2-mount program. Has
anyone else seen this or have any ideas what might be the issue.
A bit more digging. It seems the issue is seen within os-prober.
Tracking this down:
I am running Fedora29 with the 5.3.11-100.fc29.x86_64 kernel.
I have a Fedora31 rootsfs on the partition /dev/nvme0n1p2 and have
chroot'ed to this (with some /sys, /dev mounts etc). (Fedora31 would be
running the vmlinuz-5.3.15-300.fc31.x86_64 kernel).
Within the os-prober it effectively does the following at some point:
grub2-mount /dev/nvme0n1p2 /var/lib/os-prober/mount
ls /var/lib/os-prober/mount/lib*/lib*.so*
If I run:
mount /dev/nvme0n1p2 /var/lib/os-prober/mount
time ls /var/lib/os-prober/mount/lib*/lib*.so* > /dev/null
real 0m0.089s
user 0m0.028s
sys 0m0.044s
If I run:
grub2-mount /dev/nvme0n1p2 /var/lib/os-prober/mount
time ls /var/lib/os-prober/mount/lib*/lib*.so* > /dev/null
real 0m59.593s
user 0m0.190s
sys 0m0.254s
grub2-mount appears to be a FUSE driver to mount various file system
types. I am guessing that there is either a bug in grub2-mount or there
is a kernel level incompatibility (FUSE API) with the slightly older
5.3.11-100.fc29.x86_64 kernel or it is very very very very inefficient.
A minute of 100% of a CPU core to list a directory on a fast NVMe SSD!
Talk about bloatware and what about climate change folks ?
I guess this my issue in that grub2-mkconfig will take a "really" long
time on my system with largely populated rootfs (It has all of the RPM
package for development that I use so is about 28 GBytes) and this
system has an SSD and two SATA disks with multiple partitions and
operating systems.
Terry
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