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.
https://www.usenix.org/system/files/atc19-gao.pdf
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
2B
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.
--
Chris Murphy