Restore the SIMD optimization for 4.19.38 LTS, 4.14.120 LTS,
and 5.0 and newer kernels. This is accomplished by leveraging
the fact that by definition dedicated kernel threads never need
to concern themselves with saving and restoring the user FPU state.
Therefore, they may use the FPU as long as we can guarantee user
tasks always restore their FPU state before context switching back
to user space.
For the 5.0 and 5.1 kernels disabling preemption and local
interrupts is sufficient to allow the FPU to be used. All non-kernel
threads will restore the preserved user FPU state.
For 5.2 and latter kernels the user FPU state restoration will be
skipped if the kernel determines the registers have not changed.
Therefore, for these kernels we need to perform the additional
step of saving and restoring the FPU registers. Invalidating the
per-cpu global tracking the FPU state would force a restore but
that functionality is private to the core x86 FPU implementation
and unavailable.
In practice, restricting SIMD to kernel threads is not a major
restriction for ZFS. The vast majority of SIMD operations are
already performed by the IO pipeline. The remaining cases are
relatively infrequent and can be handled by the generic code
without significant impact. The two most noteworthy cases are:
1) Decrypting the wrapping key for an encrypted dataset,
i.e. `zfs load-key`. All other encryption and decryption
operations will use the SIMD optimized implementations.
2) Generating the payload checksums for a `zfs send` stream.
In order to avoid making any changes to the higher layers of ZFS
all of the `*_get_ops()` functions were updated to take in to
consideration the calling context. This allows for the fastest
implementation to be used as appropriate (see kfpu_allowed()).
The only other notable instance of SIMD operations being used
outside a kernel thread was at module load time. This code
was moved in to a taskq in order to accommodate the new kernel
thread restriction.
Finally, a few other modifications were made in order to further
harden this code and facilitate testing. They include updating
each implementations operations structure to be declared as a
constant. And allowing "cycle" to be set when selecting the
preferred ops in the kernel as well as user space.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#8754Closes#8793Closes#8965
The 5.0 kernel defines the macro ASM_BUG. In order to prevent a
conflict and build failure rename ASM_BUG to ZFS_ASM_BUG. This
is currently only an issue on aarch64 but all instances of
ASM_BUG we're renamed to avoid any future conflict on x86_64.
Reviewed-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#8725
Issue #8545
Enable vectorized raidz code on ABD buffers. The avx512f,
avx512bw, neon and aarch64_neonx2 are disabled in this commit.
With the exception of avx512bw these implementations are
updated for ABD in the subsequent commits.
Signed-off-by: Gvozden Neskovic <neskovic@gmail.com>
This re-use the framework established for SSE2, SSSE3 and
AVX2. However, GCC is using FP registers on Aarch64, so
unlike SSE/AVX2 we can't rely on the registers being left alone
between ASM statements. So instead, the NEON code uses
C variables and GCC extended ASM syntax. Note that since
the kernel explicitly disable vector registers, they
have to be locally re-enabled explicitly.
As we use the variable's number to define the symbolic
name, and GCC won't allow duplicate symbolic names,
numbers have to be unique. Even when the code is not
going to be used (e.g. the case for 4 registers when
using the macro with only 2). Only the actually used
variables should be declared, otherwise the build
will fails in debug mode.
This requires the replacement of the XOR(X,X) syntax
by a new ZERO(X) macro, which does the same thing but
without repeating the argument. And perhaps someday
there will be a machine where there is a more efficient
way to zero a register than XOR with itself. This affects
scalar, SSE2, SSSE3 and AVX2 as they need the new macro.
It's possible to write faster implementations (different
scheduling, different unrolling, interleaving NEON and
scalar, ...) for various cores, but this one has the
advantage of fitting in the current state of the code,
and thus is likely easier to review/check/merge.
The only difference between aarch64-neon and aarch64-neonx2
is that aarch64-neonx2 unroll some functions some more.
Reviewed-by: Gvozden Neskovic <neskovic@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Romain Dolbeau <romain.dolbeau@atos.net>
Closes#4801
- Implementation lock replaced with atomic variable
- Trailing whitespace is removed from user specified parameter, to enhance
experience when using commands that add newline, e.g. `echo`
- raidz_test: remove dependency on `getrusage()` and RUSAGE_THREAD, Issue #4813
- silence `cppcheck` in vdev_raidz, partial solution of Issue #1392
- Minor fixes and cleanups
- Enable use of original parity methods in [fastest] configuration.
New opaque original ops structure, representing native methods, is added
to supported raidz methods. Original parity methods are executed if selected
implementation has NULL fn pointer.
Signed-off-by: Gvozden Neskovic <neskovic@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4813
Issue #1392
This is a new implementation of RAIDZ1/2/3 routines using x86_64
scalar, SSE, and AVX2 instruction sets. Included are 3 parity
generation routines (P, PQ, and PQR) and 7 reconstruction routines,
for all RAIDZ level. On module load, a quick benchmark of supported
routines will select the fastest for each operation and they will
be used at runtime. Original implementation is still present and
can be selected via module parameter.
Patch contains:
- specialized gen/rec routines for all RAIDZ levels,
- new scalar raidz implementation (unrolled),
- two x86_64 SIMD implementations (SSE and AVX2 instructions sets),
- fastest routines selected on module load (benchmark).
- cmd/raidz_test - verify and benchmark all implementations
- added raidz_test to the ZFS Test Suite
New zfs module parameters:
- zfs_vdev_raidz_impl (str): selects the implementation to use. On
module load, the parameter will only accept first 3 options, and
the other implementations can be set once module is finished
loading. Possible values for this option are:
"fastest" - use the fastest math available
"original" - use the original raidz code
"scalar" - new scalar impl
"sse" - new SSE impl if available
"avx2" - new AVX2 impl if available
See contents of `/sys/module/zfs/parameters/zfs_vdev_raidz_impl` to
get the list of supported values. If an implementation is not supported
on the system, it will not be shown. Currently selected option is
enclosed in `[]`.
Signed-off-by: Gvozden Neskovic <neskovic@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#4328
