Slower NVMe throughput on Jetpack 5

[SanjayD]

I am seeing significantly lowered read/write speeds to my NVMe SSD on Jetpack 5.1 compared to Jetpack 4.3.

dd if=/dev/zero of=/var/tmp/tempfile bs=4k count=1000000 conv=fdatasync
1000000+0 records in
1000000+0 records out
4096000000 bytes (4.1 GB, 3.8 GiB) copied, 19.1748 s, 214 MB/s

# Clear cache
sudo sh -c "/usr/bin/echo 3 > /proc/sys/vm/drop_caches"
dd if=/var/tmp/tempfile of=/dev/null bs=4k count=1000000
1000000+0 records in
1000000+0 records out
4096000000 bytes (4.1 GB, 3.8 GiB) copied, 10.2273 s, 400 MB/s

On the older Jetpack version(4.3)

$ sudo dd if=/dev/zero of=/var/tmp/tempfile bs=4k count=1000000 conv=fdatasync
1000000+0 records in
1000000+0 records out
4096000000 bytes (4.1 GB, 3.8 GiB) copied, 5.99677 s, 683 MB/s

# clear cache
echo 3 | sudo tee /proc/sys/vm/drop_caches
 $ dd if=/var/tmp/tempfile of=/dev/null bs=4k count=1000000
1000000+0 records in
1000000+0 records out
4096000000 bytes (4.1 GB, 3.8 GiB) copied, 5.11031 s, 802 MB/s

I’m using ext4 for the SSD as well as eMMC. But I don’t see a significant difference in read/write speeds for eMMC; write ~50MB/s, read ~300MB/s

[DaneLLL]

Hi,
This is known and due to upstream kernel code. Please check the discussion in
Bad Jetpack5 nvme writing performance compared with Jetpack4 - #4 by DaneLLL

We suggest use direct read/write to achieve maximum throughput.