Currently the ARC state (MFU/MRU) of cached L2ARC buffer and their
content type is unknown. Knowing this information may prove beneficial
in adjusting the L2ARC caching policy.
This commit adds L2ARC arcstats that display the aligned size
(in bytes) of L2ARC buffers according to their content type
(data/metadata) and according to their ARC state (MRU/MFU or
prefetch). It also expands the existing evict_l2_eligible arcstat to
differentiate between MFU and MRU buffers.
L2ARC caches buffers from the MRU and MFU lists of ARC. Upon caching a
buffer, its ARC state (MRU/MFU) is stored in the L2 header
(b_arcs_state). The l2_m{f,r}u_asize arcstats reflect the aligned size
(in bytes) of L2ARC buffers according to their ARC state (based on
b_arcs_state). We also account for the case where an L2ARC and ARC
cached MRU or MRU_ghost buffer transitions to MFU. The l2_prefetch_asize
reflects the alinged size (in bytes) of L2ARC buffers that were cached
while they had the prefetch flag set in ARC. This is dynamically updated
as the prefetch flag of L2ARC buffers changes.
When buffers are evicted from ARC, if they are determined to be L2ARC
eligible then their logical size is recorded in
evict_l2_eligible_m{r,f}u arcstats according to their ARC state upon
eviction.
Persistent L2ARC:
When committing an L2ARC buffer to a log block (L2ARC metadata) its
b_arcs_state and prefetch flag is also stored. If the buffer changes
its arcstate or prefetch flag this is reflected in the above arcstats.
However, the L2ARC metadata cannot currently be updated to reflect this
change.
Example: L2ARC caches an MRU buffer. L2ARC metadata and arcstats count
this as an MRU buffer. The buffer transitions to MFU. The arcstats are
updated to reflect this. Upon pool re-import or on/offlining the L2ARC
device the arcstats are cleared and the buffer will now be counted as an
MRU buffer, as the L2ARC metadata were not updated.
Bug fix:
- If l2arc_noprefetch is set, arc_read_done clears the L2CACHE flag of
an ARC buffer. However, prefetches may be issued in a way that
arc_read_done() is bypassed. Instead, move the related code in
l2arc_write_eligible() to account for those cases too.
Also add a test and update manpages for l2arc_mfuonly module parameter,
and update the manpages and code comments for l2arc_noprefetch.
Move persist_l2arc tests to l2arc.
Reviewed-by: Ryan Moeller <freqlabs@FreeBSD.org>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
Closes#10743
Adding the FreeBSD code allows arc_summary and arcstat
to be used on FreeBSD.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@ixsystems.com>
Closes#9641
Use sys.platform to choose the correct implementation of functions and
values of variables for the platform being run on.
Reword some comments to avoid describing implementation details in the
wrong places.
Reviewed-by: Kjeld Schouten <kjeld@schouten-lebbing.nl>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Signed-off-by: Ryan Moeller <ryan@ixsystems.com>
Closes#9561
/usr/bin/env python3 is the suggested[1] shebang for Python in general
(likewise for python2) and is conventional across platforms. This eases
development on systems where python is not installed in /usr/bin
(FreeBSD for example) and makes it possible to develop in virtual
environments (venv) for isolating dependencies.
Many packaging guidelines discourage the use of /usr/bin/env, but since
this is the canonical way of writing shebangs in the Python community,
many packaging scripts are already equipped to handle substituting the
appropriate absolute path to python automatically.
Some RPM package builders lacking brp-mangle-shebangs need a small
fallback mechanism in the package spec to stamp the appropriate shebang
on installed Python scripts.
[1]: https://docs.python.org/3/using/unix.html?#miscellaneous
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Ryan Moeller <ryan@ixsystems.com>
Closes#9314
A more generic interface can be used for the abstraction of loading
kstats, allowing other platforms to implement the function cleanly.
In a similar vein, loading tunables can be abstracted away in order for
other platforms to provide their own implementations of this function.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matt Macy <mmacy@FreeBSD.org>
Signed-off-by: Ryan Moeller <ryan@ixsystems.com>
Closes#9277
Almost all of the Python code in the respository has been updated
to be compatibile with Python 2.6, Python 3.4, or newer. The only
exceptions are arc_summery3.py which requires Python 3, and pyzfs
which requires at least Python 2.7. This allows us to maintain a
single version of the code and support most default versions of
python. This change does the following:
* Sets the default shebang for all Python scripts to python3. If
only Python 2 is available, then at install time scripts which
are compatible with Python 2 will have their shebangs replaced
with /usr/bin/python. This is done for compatibility until
Python 2 goes end of life. Since only the installed versions
are changed this means Python 3 must be installed on the system
for test-runner when testing in-tree.
* Added --with-python=<2|3|3.4,etc> configure option which sets
the PYTHON environment variable to target a specific python
version. By default the newest installed version of Python
will be used or the preferred distribution version when
creating pacakges.
* Fixed --enable-pyzfs configure checks so they are run when
--enable-pyzfs=check and --enable-pyzfs=yes.
* Enabled pyzfs for Python 3.4 and newer, which is now supported.
* Renamed pyzfs package to python<VERSION>-pyzfs and updated to
install in the appropriate site location. For example, when
building with --with-python=3.4 a python34-pyzfs will be
created which installs in /usr/lib/python3.4/site-packages/.
* Renamed the following python scripts according to the Fedora
guidance for packaging utilities in /bin
- dbufstat.py -> dbufstat
- arcstat.py -> arcstat
- arc_summary.py -> arc_summary
- arc_summary3.py -> arc_summary3
* Updated python-cffi package name. On CentOS 6, CentOS 7, and
Amazon Linux it's called python-cffi, not python2-cffi. For
Python3 it's called python3-cffi or python3x-cffi.
* Install one version of arc_summary. Depending on the version
of Python available install either arc_summary2 or arc_summary3
as arc_summary. The user output is only slightly different.
Reviewed-by: John Ramsden <johnramsden@riseup.net>
Reviewed-by: Neal Gompa <ngompa@datto.com>
Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#8096
