Long mount time of ESP FAT partition

Long mount time of ESP FAT partition

[Paul Menzel]

Dear Linux folks,


On a Dell Precision 3540 with Debian sid/unstable, Linux 6.1.12 takes 
1.5 seconds to mount the 128 MB FAT partition `/dev/nvme0n1p1` to 
`/boot/efi`.

```
$ lsblk --fs
NAME                FSTYPE      FSVER LABEL UUID 
         FSAVAIL FSUSE% MOUNTPOINTS
nvme0n1 

├─nvme0n1p1         vfat        FAT32 ESP   381C-FF6C 
           49.2M    61% /boot/efi
├─nvme0n1p2         crypto_LUKS 2 
b88be798-13e3-4884-9748-bf7a23f0ae87
│ └─nvme0n1p2_crypt ext4        1.0 
c9342a55-b747-4442-b2f4-bc03eb7a51cf    733G    17% /
└─nvme0n1p3         ext4        1.0   boot 
16743b63-5a4f-404e-a46e-2db5add63980  303.6M    10% /boot
$ more /etc/fstab
[…]
/dev/disk/by-uuid/c9342a55-b747-4442-b2f4-bc03eb7a51cf /  auto 
defaults,errors=remount-ro 0   1
/dev/disk/by-uuid/16743b63-5a4f-404e-a46e-2db5add63980 /boot  auto 
defaults,errors=remount-ro      0       1
UUID=381C-FF6C  /boot/efi       vfat    umask=0022      0       1
$ journalctl -b -u boot.mount -o short-precise
Feb 28 11:19:14.006616 morley systemd[1]: Mounting boot.mount - /boot...
Feb 28 11:19:14.013246 morley systemd[1]: Mounted boot.mount - /boot.
$ journalctl -b -u boot-efi.mount -o short-precise
Feb 28 11:19:14.014469 morley systemd[1]: Mounting boot-efi.mount - 
/boot/efi...
Feb 28 11:19:15.550770 morley systemd[1]: Mounted boot-efi.mount - 
/boot/efi.
```

On a Dell Latitude E7250 mounting a 128 MB FAT partition `/dev/sda1` 
(SAMSUNG SSD PM851 mSATA 256GB) only takes 90 ms.

```
$ journalctl -u boot-efi.mount -o short-monotonic -b
[   10.693263] ersatz systemd[1]: Mounting boot-efi.mount - /boot/efi...
[   10.783176] ersatz systemd[1]: Mounted boot-efi.mount - /boot/efi.
```


Kind regards,

Paul

Re: Long mount time of ESP FAT partition

[OGAWA Hirofumi]

Paul Menzel <pmenzel@molgen.mpg.de> writes:

> $ journalctl -b -u boot-efi.mount -o short-precise
> Feb 28 11:19:14.014469 morley systemd[1]: Mounting boot-efi.mount - 
> /boot/efi...
> Feb 28 11:19:15.550770 morley systemd[1]: Mounted boot-efi.mount - 
> /boot/efi.
> ```

This mount is always slow? For example, simply unmount and mount by
command is also slow after finished boot sequence?

Since that operation of log would include too many syscalls, we have to
find which syscall is slow. Then check the detail of it (e.g. I/O
request).

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>