Input/Output: MacOS Sonoma 14.4b3 CIRCUITPY Slow Write Performance #8918
Description
CircuitPython version
All CP versions are affected.Code/REPL
n/aBehavior
Writes to the CIRCUITPY filesystem when mounted by USB MSC on MacOS Sonoma 14.4 beta 2 and above are 400 to 800 times slower than with previous releases of MacOS.
Description
Previously, MacOS Sonoma 14.0 introduced a regression in its MSDOS filesystem support that caused a number of issues that are documented in issue #8449. The root cause of the issue was in Sonoma's new MSDOS filesystem user-space support that replaced the earlier kernel extension support. The new user-space support delays writing filesystem metadata (in this case FAT table and root directory) for tens of seconds after writes to a file, causing a variety of undesirable outcomes.
Apple subsequently fixed this behavior in 14.4 beta 2 by completely re-writing all metadata (the equivalent of a sync) after every few blocks written. This has the undesirable effects of slowing writes by 400 to 800 times and introducing unnecessary wear to the flash memory.
It is possible to reproduce poor write performance using a USB stick. All of these tests were performed with a 16G stick. The test writes 512 blocks of 512 bytes of zeroes.
dd if=/dev/zero of=/Volumes/NO\ NAME/test.dat bs=512 count=512
Performance jumps ~400x to 800x when the filesystem size exceeds 1G.
| Filesystem Size | Filesystem | Time(Sec.) |
|---|---|---|
| 4M | FAT12 | 26.981 |
| 8M | FAT12 | 28.780 |
| 15M | FAT16 | 29.019 |
| 16M | FAT16 | 29.139 |
| 32M | FAT16 | 29.669 |
| 64M | FAT16 | 29.414 |
| 128M | FAT16 | 50.138 |
| 256M | FAT32 | 39.641 |
| 512M | FAT32 | 40.786 |
| 1G | FAT32 | 42.938 |
| 2G | FAT32 | 0.050 |
| 4G | FAT32 | 0.046 |
| 8G | FAT32 | 0.101 |
| 16G | FAT32 | 0.109 |
For convenience I made the test sticks on Linux. It should be possible to do the same with Disk Utilities on MacOS.
Partitioned with fdisk creating a primary partition of the desired size, for example:
rabeles@ub2004:~$ sudo fdisk /dev/sdd
Welcome to fdisk (util-linux 2.37.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): d
Selected partition 1
Partition 1 has been deleted.
Command (m for help): n
Partition type
p primary (0 primary, 0 extended, 4 free)
e extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1):
First sector (2048-30892031, default 2048):
Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-30892031, default 30892031): +1026M
Created a new partition 1 of type 'Linux' and of size 1 GiB.
Partition #1 contains a vfat signature.
Do you want to remove the signature? [Y]es/[N]o: yes
The signature will be removed by a write command.
Command (m for help): t
Selected partition 1
Hex code or alias (type L to list all): 06
Changed type of partition 'Linux' to 'FAT16'.
Command (m for help): p
Disk /dev/sdd: 14.73 GiB, 15816720384 bytes, 30892032 sectors
Disk model: Cruzer Blade
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000
Device Boot Start End Sectors Size Id Type
/dev/sdd1 2048 2103295 2101248 1G 6 FAT16
Filesystem/RAID signature on partition 1 will be wiped.
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
Then create the filesystem:
rabeles@ub2004:~$ sudo mkfs.vfat -F32 /dev/sdd1
mkfs.fat 4.2 (2021-01-31)
Additional information
No response