VCD tracing is now parallelized using the same thread pool as the model.
We achieve this by breaking the top level trace functions into multiple
top level functions (as many as --threads), and after emitting the time
stamp to the VCD file on the main thread, we execute the tracing
functions in parallel on the same thread pool as the model (which we
pass to the trace file during registration), tracing into a secondary
per thread buffer. The main thread will then stitch (memcpy) the buffers
together into the output file.
This makes the `--trace-threads` option redundant with `--trace`, which
now only affects `--trace-fst`. FST tracing uses the previous offloading
scheme.
This obviously helps a lot in VCD tracing performance, and I have seen
better than Amdahl speedup, namely I get 3.9x on XiangShan 4T (2.7x on
OpenTitan 4T).
The --prof-threads option has been split into two independent options:
1. --prof-exec, for collecting verilator_gantt and other execution
related profiling data, and
2. --prof-pgo, for collecting data needed for PGO
The implementation of execution profiling is extricated from
VlThreadPool and is now a separate class VlExecutionProfiler. This means
--prof-exec can now be used for single-threaded models (though it does
not measure a lot of things just yet). For consistency VerilatedProfiler
is renamed VlPgoProfiler. Both VlExecutionProfiler and VlPgoProfiler are
in verilated_profiler.{h/cpp}, but can be used completely independently.
Also re-worked the execution profile format so it now only emits events
without holding onto any temporaries. This is in preparation for some
future optimizations that would be hindered by the introduction of function
locals via AstText.
Also removed the Barrier event. Clearing the profile buffers is not
notably more expensive as the profiling records are trivially
destructible.
This is to allow C++ verilator toplevel to support
multiple modes of waveform tracing
VM_TRACE_FST can be used inside a #if VM_TRACE
section to switch between classic .vcd tracing and the
more compact .fst format supported by GTKWAVE
* Add a test to use shared object of protect-lib
* Add a guard to call ctor/dtor just once even when a protec-lib is shared object.
* Pass .a to linker in leaf-last order for older ld.
* Add -flat_namespace for mac
* No need to link the intermediate .so in hierarchical verilation
* apply clang-format
* run all tests in ci instead of cron. DONT_MERGE
* Add -undefined dynamic_lookup for mac environment when linking a shared protect-lib.
* Let's just check on mac for now. DONT_MERGE
* Revert "Let's just check on mac for now. DONT_MERGE"
This reverts commit 533fac6f9f.
* Revert "run all tests in ci instead of cron. DONT_MERGE"
This reverts commit fb4ac1fb42.
Convert trace buffer to 32-bit entries, rather than a union containing a
pointer type. Also tweaked trace entry layouts for a bit more
performance. This gains another 10% on SweRV EH1 CoreMark.
We used to include a .cpp file on the link line for the shared library,
which was ignored, but generated a .d file for the .so which contained
the header files required by the .cpp file. This then caused a rebuild
where we included the .d in verilated.mk to included in the .h headers
among the prerequisites of the .so, yielding a clang error about treating
.h files as c++-header rather than c-header... Long story short, we don't
do that anymore. This used t cause t_a4_examples to fail on occasion.
Note there is no need for a separate compilation rule for the
<--protect-lib>.cpp, as it will jsut pick up the standard OPT_FAST rule.
The --trace-threads option can now be used to perform tracing on a
thread separate from the main thread when using VCD tracing (with
--trace-threads 1). For FST tracing --trace-threads can be 1 or 2, and
--trace-fst --trace-threads 1 is the same a what --trace-fst-threads
used to be (which is now deprecated).
Performance numbers on SweRV EH1 CoreMark, clang 6.0.0, Intel i7-3770 @
3.40GHz, IO to ramdisk, with numactl set to schedule threads on different
physical cores. Relative speedup:
--trace -> --trace --trace-threads 1 +22%
--trace-fst -> --trace-fst --trace-threads 1 +38% (as --trace-fst-thread)
--trace-fst -> --trace-fst --trace-threads 2 +93%
Speed relative to --trace with no threaded tracing:
--trace 1.00 x
--trace --trace-threads 1 0.82 x
--trace-fst 1.79 x
--trace-fst --trace-threads 1 1.23 x
--trace-fst --trace-threads 2 0.87 x
This means FST tracing with 2 extra threads is now faster than single
threaded VCD tracing, and is on par with threaded VCD tracing. You do
pay for it in total compute though as --trace-fst --trace-threads 2 uses
about 240% CPU vs 150% for --trace-fst --trace-threads 1, and 155% for
--trace --trace threads 1. Still for interactive use it should be
helpful with large designs.
The intention was that all subclasses of AstNode which are
intermediate must be abstract as well and called AstNode*. This was
violated recently by 28b9db1903. This
patch restores that property by:
- Renaming AstFile to AstNodeFile
- Introducing AstNodeSimpleText as the common base of AstText and
AstTextBlock, rather than AstTextBlock deriving from AstText.
Geza Lore
Wilson Snyder
HungMingWu
Julien Margetts
Àlex Torregrosa
Markus Krause
Yutetsu TAKATSUKASA