Add support for event overflows when the host thread migrates across
differnt types of cores on a hybrid host architecture. This patch
achieves this by simply halving the sample period for each performance
counter. Since there are two types of cores, this guarantees that an
overflow event will trigger before N events occur, where N is the
requested period (e.g., number of instructions to simulate). This
may result in many early triggers (up to log2(N)) before the requested
period is reached. However, gem5's existing bookkeeping logic already
handles this case properly: if fewer events than requested occurred,
it will set a new period (N - observed) and resume execution. This loop
will exit once N events have actually occurred.
Change-Id: Iff85237da1ae1aa25bc2045fbf9091726291fe36
Fix#1064 by adding support for hardware performance counters on hybrid
architectures like Intel Alder Lake.
Hybrid architectures have multiple types of cores, each of which require
the instantiation of a separate performance counter. The KVM CPU's
PerfKvmCounter class was not aware of this, any only instantiated a
single performance counter, implicitly bound to the P-core only. This
meant that if gem5 ever ran on an E-core, the various hardware
performance counters would not get updated properly, in some cases
always zero (e.g., for the number of instructions executed).
This patch adds support for hybrid host architectures as follows. First,
we convert PerfKvmCounter into an abstract class, which has two
concrete implementations: SimplePerfKvmCounter and HybridPerfKvmCounter.
The former is used for non-hybrid architectures or for non-hardware
performance counters and is functionally equivalent to the prior
implementation of PerfKvmCounter. The latter is used for instantiating
hardware performance counters (i.e., of type PERF_TYPE_HARDWARE) on
hybrid host architectures. It does so by internally instantiating two
SimplePerfKvmCounters, one for a P-core and one for an E-core. Upon
read, it sums the results of reading the two internal counters.
Change-Id: If64fcb0e2fcc1b3a6a37d77455c2b21e1fc81150
The CL updates the Kconfig:
1. Replace the USE_NULL_ISA with BUILD_ISA
2. The USE_XXX_ISAs are depends on BUILD_ISA
3. If the BUILD_ISA is set, at least one of USE_XXX_ISAs must be set
4. Refactor the USE_KVM option
Change-Id: I2a600dea9fb671263b0191c46c5790ebbe91a7b8
These are not yet consumed by anything, but convert all the settings
from SCons variables to Kconfig variables.
If you have existing SConsopts files which need to be converted, you
should take a look at KCONFIG.md to learn about how kconfig is used in
gem5. You should decide if any variables need to be available to C++ or
kconfig itself, and whether those are options which should be detected
automatically, or should be up to the user. Options which should be
measured automatically should still be in SConsopts files, while user
facing options should be added to new or existing Kconfig files.
Generally, make sure you're storing c++/kconfig visible options in
env['CONF'][...]. Also remove references to sticky_vars since persistent
options should now be handled with kconfig, and export_vars since
everything in env['CONF'] is now exported automatically.
Switch SCons/gem5 to use Kconfig for configuration, except EXTRAS which
is still a sticky SCons variable. This is necessary because EXTRAS also
controls what config options exist. If it came from Kconfig itself, then
there would be a circular dependency. This dependency could
theoretically be handled by reparsing the Kconfig when EXTRAS
directories were added or removed, but that would be complicated, and
isn't supported by kconfiglib. It wouldn't be worth the significant
effort it would take to add it, just to use Kconfig more purely.
Change-Id: I29ab1940b2d7b0e6635a490452d05befe5b4a2c9
* cpu-kvm: Add a variable signifying whether we are using perf
Change-Id: Iaa081e364f85c863f781723b5524d267724ed0e4
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
* cpu-kvm: Making it clear the functionalities are specific to KVM
Change-Id: I982426f294d90655227dc15337bf73c42a260ded
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
* cpu-kvm: Make perf optional
Change-Id: I8973c2a96575383976cea7ca3fda478f83e95c3f
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
* configs: Add an example config of using KVM without perf
Change-Id: Ic69fa7dac4f1a2c8fe23712b0fa77b5b22c5f2df
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
* Apply suggestions from code review
Co-authored-by: Jason Lowe-Power <jason@lowepower.com>
* misc: Add an example to the panic
Change-Id: Ic1fdfb955e5d8b9ad1d4f0a2bf30fa8050deba70
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
* misc: Add warning of not using perf when using KVM CPU
Change-Id: I96c0832fb48c63a79773665ca6228da778ef0497
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
* misc: Fix stuff
Change-Id: Ib407ae7407955b695f0e0f2718324f41bb0d768f
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
* misc: style fix
Change-Id: I7275942e43f46140fdd52c975f76abb3c81b8b0a
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
---------
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Co-authored-by: Jason Lowe-Power <jason@lowepower.com>
The KVM_ISA setting was moved into a CONF dict, but the code which
ensured it had a default if there was no possible KVM hosting ISA was
still setting that variable in the base environment dict. This moves
the setting into the CONF dict instead.
Change-Id: I067c969dd761b2cdb098bcba6cd6a4b643d2d427
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/63752
Reviewed-by: Earl Ou <shunhsingou@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
The TARGET_ISA variable would let you select one ISA from a list of
possible ISAs. That has now been replaced with USE_ARM_ISA, USE_X86_ISA,
etc, variables which are boolean on or off. That will allow any number
of ISAs to be enabled or disabled individually. Enabling something other
than exactly one of these will probably prevent you from getting a
working gem5 binary, but those problems are being addressed in other,
parallel change series.
I decided to use the USE_ prefix since it was consistent with most other
on/off variables we have in gem5. One noteable exception is the
BUILD_GPU setting which, you could convincingly argue, is a better
prefix than USE_. Another option would be to use CONFIG_, in
anticipation of using a kconfig style config mechanism in gem5.
It seemed premature to start using a CONFIG_ prefix here, and if we
decide to switch to some other prefix like BUILD_, it should be a
purposeful choice and not something somebody just starts using.
Change-Id: I90fef2835aa4712782e6c1313fbf564d0ed45538
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52491
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
This makes what are configuration and what are internal SCons variables
explicit and separate, and makes it unnecessary to call out what
variables to export to C++.
These variables will also be plumbed into and out of kconfiglib in later
changes.
Change-Id: Iaf5e098d7404af06285c421dbdf8ef4171b3f001
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56892
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
* The value of build environment variable KVM_ISA is serialized into
the generated file `kvm_isa.hh'. This value should be a string, but on
hosts where the KVM headers are not available, the default `None` is
inserted. Changed the default value to the string `""` in this case.
* Added missing include for `std::array`.
Change-Id: I651122cc46fc9c0757f592b05f4b4cab285cb91f
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/57889
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
The KvmVM will declare itself to the System object, instead of the other
way around. This way the System object can just keep an opaque KvmVM
pointer which does not depend on the KvmVM code even being compiled into
gem5. If there is a KvmVM object, that can more safely assume there is a
corresponding System object to attach itself to.
Also move use of the KvmVM pointer out of constructors, since the VM may
not have registered itself with the System object yet. Those uses can
happen in the init() method instead.
Change-Id: Ia0842612b101315bc1af0232d7f5ae2b55a15922
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56187
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
As described in a comment in the base KVM CPU, there needs to be a way
to set the next PC of a PCState object to the actual current PC. Since
this is the only place that sort of operation is needed and it's a bit
of a hack to get around a quirk of calling pseudo instructions in a KVM
CPU, we can support it by adding a virtual method for it which is
implemented by the ISA specific subclasses of the KVM CPU.
Change-Id: Idf390e9c4ffa7398cd08e76846c61cb6da754dce
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52059
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Gabe Black <gabe.black@gmail.com>
When allocating memory with operator new(size_t), we should also delete
that memory with operator delete(). Note that this is a generic form of
new and delete which do not construct an object in the allocated space,
or delete the object when freeing the space.
There were a number of places where we were over-allocating a structure
so that there would be room after it for other data, at least sometimes
to allocate C structures which would have a trailing array of some other
structure with an undefined size. Those structures were then being
stored in a std::unique_ptr with the default deleter, which just calls
full blown delete and not operator delete.
It seems that this is often ok, and I was not able to find anything that
spelled out in bold letters that it isn't. I did find this sentence:
"If the pointer passed to the standard library deallocation function was
not obtained from the corresponding standard library allocation function,
the behavior is undefined."
On this webpage:
https://en.cppreference.com/w/cpp/memory/new/operator_delete
This is a *little* vague, since they might mean you can't mix malloc and
delete, or new and free. Strictly interpretting it though, it could mean
you can't mix operator new with regular delete, or any other mismatched
combination.
I also found that exactly how this causes problems depends on what heap
allocator you're using. When I used tcmalloc, gem5 would segfault within
that library. When I disabled tcmalloc to run valgrind, the segfault
went away. I think this may be because sometimes you get lucky and
undefined behavior is what you actually wanted, and sometimes you don't.
To fix this problem, this change overrides the deleter on all of these
unique_ptr-s so that they use operator delete. Also, it refactors some
code in arch/x86/kvm/x86_cpu.cc so that the function that allocates
memory with operator new returns a std::unique_ptr instead of a raw
pointer. This raw pointer was always immediately put into a unique_ptr
anyway, and, in addition to tidying up the call sights slightly, also
avoids having to define a custom deleter in each of those locations
instead of once in the allocation function.
Change-Id: I9ebff430996cf603051f5baa8708424819ed8465
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52383
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Gabe Black <gabe.black@gmail.com>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
The x86 KVM CPU had been in the cpu/kvm directory, while the arm CPU was
inconsistently in the arch/arm directory.
This change moves the x86 CPU to be in arch/x86, restoring consistency.
This location will make the KVM support more modular, by not having the
x86 CPU implementation right alongside the generic implementation.
Change-Id: Ia13151f843df8f8877bfef5ff620825877d3dffa
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52085
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Apply the gem5 namespace to the codebase.
Some anonymous namespaces could theoretically be removed,
but since this change's main goal was to keep conflicts
at a minimum, it was decided not to modify much the
general shape of the files.
A few missing comments of the form "// namespace X" that
occurred before the newly added "} // namespace gem5"
have been added for consistency.
std out should not be included in the gem5 namespace, so
they weren't.
ProtoMessage has not been included in the gem5 namespace,
since I'm not familiar with how proto works.
Regarding the SystemC files, although they belong to gem5,
they actually perform integration between gem5 and SystemC;
therefore, it deserved its own separate namespace.
Files that are automatically generated have been included
in the gem5 namespace.
The .isa files currently are limited to a single namespace.
This limitation should be later removed to make it easier
to accomodate a better API.
Regarding the files in util, gem5:: was prepended where
suitable. Notice that this patch was tested as much as
possible given that most of these were already not
previously compiling.
Change-Id: Ia53d404ec79c46edaa98f654e23bc3b0e179fe2d
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/46323
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Matthew Poremba <matthew.poremba@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>
As part of recent decisions regarding namespace
naming conventions, all namespaces will be changed
to snake case.
::Stats became ::statistics.
"statistics" was chosen over "stats" to avoid generating
conflicts with the already existing variables (there are
way too many "stats" in the codebase), which would make
this patch even more disturbing for the users.
Change-Id: If877b12d7dac356f86e3b3d941bf7558a4fd8719
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/45421
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
As part of recent decisions regarding namespace
naming conventions, all namespaces will be changed
to snake case.
sim_clock::Float became sim_clock::as_float.
"as_float" was chosen because "float" is a reserved
keywords, and this namespace acts as a selector of
how to read the internal variables. Another
possibility to resolve this would be to remove the
namespaces "Float" and "Int" and use unions instead.
Change-Id: I7b3d9c6e9ab547493d5596c7eda080a25509a730
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/45435
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Maintainer: Gabe Black <gabe.black@gmail.com>
