On Mon, Jan 20, 2020 at 1:38 AM Bohdan Khomutskyi <bkhomuts(a)redhat.com> wrote:
In my previous message, I mentioned that CPU is underutilized during installation. I
haven't investigated further why, but I suspect it's due to the inefficiency
caused by the usage of the loop device and/or inefficiency in the rsync itself.
Could this be read amplification?
This paper on erofs suggests read amplification can be a significant
side effect with squashfs. It could be exacerbated with random reads,
and I expect it gets worse with larger block size. That's probably
mitigated with unsquashfs.
Specifically page 4, 2nd paragraph.
This also makes me wonder about the memory consumption effect of a 1M
block size, especially for Fedora ARM where it looks like Raspberry Pi
Most of the ARM images are raw.xz but some are bootable ISOs, dvd and
netinstall. And those contain a squashfs sysroot. Even if there's no
out of memory problem, it could result in paging. All ISOs setup
swap-on-ZRAM these days, lives, DVD, and netinstall. I think the ARM
case needs testing before committing to 1M block size across all ISOs,
or implementing changes in Fedora release engineering.