[PATCHSET 06/18] mkfs: scale shards on ssds

Darrick J. Wong
2024-03-26T02:56:18Z

Hi all,

For a long time, the maintainers have had a gut feeling that we could
optimize performance of XFS filesystems on non-mechanical storage by
scaling the number of allocation groups to be a multiple of the CPU
count.

With modern ~2022 hardware, it is common for systems to have more than
four CPU cores and non-striped SSDs ranging in size from 256GB to 4TB.
The default mkfs geometry still defaults to 4 AGs regardless of core
count, which was settled on in the age of spinning rust.

This patchset adds a different computation for AG count and log size
that is based entirely on a desired level of concurrency. If we detect
storage that is non-rotational (or the sysadmin provides a CLI option),
then we will try to match the AG count to the CPU count to minimize AGF
contention and make the log large enough to minimize grant head
contention.

If you're going to start using this code, I strongly recommend pulling
from my git trees, which are linked below.

This has been running on the djcloud for months with no problems. Enjoy!
Comments and questions are, as always, welcome.

--D

xfsprogs git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=mkfs-scale-geo-on-ssds

fstests git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfstests-dev.git/log/?h=mkfs-scale-geo-on-ssds
---
Commits in this patchset:
* mkfs: allow sizing allocation groups for concurrency
* mkfs: allow sizing internal logs for concurrency
---
man/man8/mkfs.xfs.8.in | 46 +++++++++
mkfs/xfs_mkfs.c | 251 +++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 291 insertions(+), 6 deletions(-)