[RFC v2 PATCH 0/7] Introduce nfs-readahead-udev

[Thiago Becker <tbecker@redhat.com>]

Recent changes in the linux kernel caused NFS readahead to default to
128 from the previous default of 15 * rsize. This causes performance
penalties to some read-heavy workloads, which can be fixed by
tuning the readahead for that given mount.

Specifically, the read troughput on a sec=krb5p mount drops by 50-75%
when comparing the default readahead with a readahead of 15360.

Previous discussions:
https://lore.kernel.org/linux-nfs/20210803130717.2890565-1-trbecker@gmail.com/
I attempted to add a non-kernel option to mount.nfs, and it was
rejected.

https://lore.kernel.org/linux-nfs/20210811171402.947156-1-trbecker@gmail.com/
Attempted to add a mount option to the kernel, rejected as well.

I had started a separate tool to set the readahead of BDIs, but the
scope is specifically for NFS, so I would like to get the community
feeling for having this in nfs-utils.

This patch series introduces nfs-readahead-udev, a utility to
automatically set NFS readahead when NFS is mounted. The utility is
triggered by udev when a new BDI is added, returns to udev the value of
the readahead that should be used.

The tool currently supports setting read ahead per mountpoint, nfs major
version, or by a global default value.

Thiago Becker (7):
  Create nfs-readahead-udev
  readahead: configure udev
  readahead: create logging facility
  readahead: only set readahead for nfs devices.
  readahead: create the configuration file
  readahead: add mountpoint and fstype options
  readahead: documentation

 .gitignore                                    |   6 +
 configure.ac                                  |   4 +
 tools/Makefile.am                             |   2 +-
 tools/nfs-readahead-udev/99-nfs_bdi.rules.in  |   1 +
 tools/nfs-readahead-udev/Makefile.am          |  26 +++
 tools/nfs-readahead-udev/config_parser.c      |  25 +++
 tools/nfs-readahead-udev/config_parser.h      |  14 ++
 tools/nfs-readahead-udev/list.h               |  48 ++++
 tools/nfs-readahead-udev/log.h                |  16 ++
 tools/nfs-readahead-udev/main.c               | 211 ++++++++++++++++++
 .../nfs-readahead-udev/nfs-readahead-udev.man |  47 ++++
 tools/nfs-readahead-udev/parser.y             |  85 +++++++
 tools/nfs-readahead-udev/readahead.conf       |  15 ++
 tools/nfs-readahead-udev/scanner.l            |  19 ++
 tools/nfs-readahead-udev/syslog.c             |  47 ++++
 15 files changed, 565 insertions(+), 1 deletion(-)
 create mode 100644 tools/nfs-readahead-udev/99-nfs_bdi.rules.in
 create mode 100644 tools/nfs-readahead-udev/Makefile.am
 create mode 100644 tools/nfs-readahead-udev/config_parser.c
 create mode 100644 tools/nfs-readahead-udev/config_parser.h
 create mode 100644 tools/nfs-readahead-udev/list.h
 create mode 100644 tools/nfs-readahead-udev/log.h
 create mode 100644 tools/nfs-readahead-udev/main.c
 create mode 100644 tools/nfs-readahead-udev/nfs-readahead-udev.man
 create mode 100644 tools/nfs-readahead-udev/parser.y
 create mode 100644 tools/nfs-readahead-udev/readahead.conf
 create mode 100644 tools/nfs-readahead-udev/scanner.l
 create mode 100644 tools/nfs-readahead-udev/syslog.c

-- 
2.35.1