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cpu-kvm: Make using perf when using KVM CPU optional (#95)

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* 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>
This commit is contained in:
Hoa Nguyen
2023-07-20 10:34:44 -07:00
committed by Bobby R. Bruce
parent 919dd5efbd
commit 41abc6ab77
5 changed files with 221 additions and 29 deletions
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138
configs/example/gem5_library/x86-ubuntu-run-with-kvm-no-perf.py Normal file
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@@ -0,0 +1,138 @@
# Copyright (c) 2023 The Regents of the University of California
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met: redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer;
# redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution;
# neither the name of the copyright holders nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""
This script demonstrates how to use KVM CPU without perf.
This simulation boots Ubuntu 18.04 using 2 KVM CPUs without using perf.
Usage
-----
```
scons build/X86/gem5.opt -j`nproc`
./build/X86/gem5.opt configs/example/gem5_library/x86-ubuntu-run-with-kvm-no-perf.py
```
"""
from gem5.utils.requires import requires
from gem5.components.boards.x86_board import X86Board
from gem5.components.cachehierarchies.ruby.mesi_two_level_cache_hierarchy import (
MESITwoLevelCacheHierarchy,
)
from gem5.components.memory.single_channel import SingleChannelDDR4_2400
from gem5.components.processors.simple_switchable_processor import (
SimpleSwitchableProcessor,
)
from gem5.components.processors.cpu_types import CPUTypes
from gem5.isas import ISA
from gem5.coherence_protocol import CoherenceProtocol
from gem5.simulate.simulator import Simulator
from gem5.simulate.exit_event import ExitEvent
from gem5.resources.workload import Workload
# This simulation requires using KVM with gem5 compiled for X86 simulation
# and with MESI_Two_Level cache coherence protocol.
requires(
isa_required=ISA.X86,
coherence_protocol_required=CoherenceProtocol.MESI_TWO_LEVEL,
kvm_required=True,
)
from gem5.components.cachehierarchies.ruby.mesi_two_level_cache_hierarchy import (
MESITwoLevelCacheHierarchy,
)
cache_hierarchy = MESITwoLevelCacheHierarchy(
l1d_size="32KiB",
l1d_assoc=8,
l1i_size="32KiB",
l1i_assoc=8,
l2_size="512KiB",
l2_assoc=16,
num_l2_banks=1,
)
# Main memory
memory = SingleChannelDDR4_2400(size="3GiB")
# This is a switchable CPU. We first boot Ubuntu using KVM, then the guest
# will exit the simulation by calling "m5 exit" (see the `command` variable
# below, which contains the command to be run in the guest after booting).
# Upon exiting from the simulation, the Exit Event handler will switch the
# CPU type (see the ExitEvent.EXIT line below, which contains a map to
# a function to be called when an exit event happens).
processor = SimpleSwitchableProcessor(
starting_core_type=CPUTypes.KVM,
switch_core_type=CPUTypes.TIMING,
isa=ISA.X86,
num_cores=2,
)
# Here we tell the KVM CPU (the starting CPU) not to use perf.
for proc in processor.start:
proc.core.usePerf = False
# Here we setup the board. The X86Board allows for Full-System X86 simulations.
board = X86Board(
clk_freq="3GHz",
processor=processor,
memory=memory,
cache_hierarchy=cache_hierarchy,
)
# Here we set the Full System workload.
# The `set_kernel_disk_workload` function for the X86Board takes a kernel, a
# disk image, and, optionally, a command to run.
# This is the command to run after the system has booted. The first `m5 exit`
# will stop the simulation so we can switch the CPU cores from KVM to timing
# and continue the simulation to run the echo command, sleep for a second,
# then, again, call `m5 exit` to terminate the simulation. After simulation
# has ended you may inspect `m5out/system.pc.com_1.device` to see the echo
# output.
command = (
"m5 exit;"
+ "echo 'This is running on Timing CPU cores.';"
+ "sleep 1;"
+ "m5 exit;"
)
workload = Workload("x86-ubuntu-18.04-boot")
workload.set_parameter("readfile_contents", command)
board.set_workload(workload)
simulator = Simulator(
board=board,
on_exit_event={
# Here we want override the default behavior for the first m5 exit
# exit event. Instead of exiting the simulator, we just want to
# switch the processor. The 2nd m5 exit after will revert to using
# default behavior where the simulator run will exit.
ExitEvent.EXIT: (func() for func in [processor.switch])
},
)
simulator.run()

5
src/cpu/kvm/BaseKvmCPU.py
View File

@@ -64,6 +64,11 @@ class BaseKvmCPU(BaseCPU):
def support_take_over(cls):
return True
usePerf = Param.Bool(
True,
"Use perf for gathering statistics from the guest and providing "
"statistic-related functionalities",
)
useCoalescedMMIO = Param.Bool(False, "Use coalesced MMIO (EXPERIMENTAL)")
usePerfOverflow = Param.Bool(
False, "Use perf event overflow counters (EXPERIMENTAL)"

84
src/cpu/kvm/base.cc
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@@ -71,12 +71,15 @@ BaseKvmCPU::BaseKvmCPU(const BaseKvmCPUParams &params)
alwaysSyncTC(params.alwaysSyncTC),
threadContextDirty(true),
kvmStateDirty(false),
usePerf(params.usePerf),
vcpuID(-1), vcpuFD(-1), vcpuMMapSize(0),
_kvmRun(NULL), mmioRing(NULL),
pageSize(sysconf(_SC_PAGE_SIZE)),
tickEvent([this]{ tick(); }, "BaseKvmCPU tick",
false, Event::CPU_Tick_Pri),
activeInstPeriod(0),
hwCycles(nullptr),
hwInstructions(nullptr),
perfControlledByTimer(params.usePerfOverflow),
hostFactor(params.hostFactor), stats(this),
ctrInsts(0)
@@ -96,6 +99,22 @@ BaseKvmCPU::BaseKvmCPU(const BaseKvmCPUParams &params)
thread->setStatus(ThreadContext::Halted);
tc = thread->getTC();
threadContexts.push_back(tc);
if ((!usePerf) && perfControlledByTimer) {
panic("KVM: invalid combination of parameters: cannot use "
"perfControlledByTimer without usePerf\n");
}
// If we use perf, we create new PerfKVMCounters
if (usePerf) {
hwCycles = std::unique_ptr<PerfKvmCounter>(new PerfKvmCounter());
hwInstructions = std::unique_ptr<PerfKvmCounter>(new PerfKvmCounter());
} else {
inform("Using KVM CPU without perf. The stats related to the number "
"of cycles and instructions executed by the KVM CPU will not "
"be updated. The stats should not be used for performance "
"evaluation.");
}
}
BaseKvmCPU::~BaseKvmCPU()
@@ -248,7 +267,7 @@ BaseKvmCPU::restartEqThread()
setupCounters();
if (p.usePerfOverflow) {
runTimer.reset(new PerfKvmTimer(hwCycles,
runTimer.reset(new PerfKvmTimer(*hwCycles,
KVM_KICK_SIGNAL,
p.hostFactor,
p.hostFreq));
@@ -424,8 +443,10 @@ BaseKvmCPU::notifyFork()
vcpuFD = -1;
_kvmRun = NULL;
hwInstructions.detach();
hwCycles.detach();
if (usePerf) {
hwInstructions->detach();
hwCycles->detach();
}
}
}
@@ -690,7 +711,9 @@ BaseKvmCPU::kvmRunDrain()
uint64_t
BaseKvmCPU::getHostCycles() const
{
return hwCycles.read();
if (usePerf)
return hwCycles->read();
return 0;
}
Tick
@@ -746,21 +769,26 @@ BaseKvmCPU::kvmRun(Tick ticks)
// Get hardware statistics after synchronizing contexts. The KVM
// state update might affect guest cycle counters.
uint64_t baseCycles(getHostCycles());
uint64_t baseInstrs(hwInstructions.read());
uint64_t baseInstrs = 0;
if (usePerf) {
baseInstrs = hwInstructions->read();
}
// Arm the run timer and start the cycle timer if it isn't
// controlled by the overflow timer. Starting/stopping the cycle
// timer automatically starts the other perf timers as they are in
// the same counter group.
runTimer->arm(ticks);
if (!perfControlledByTimer)
hwCycles.start();
if (usePerf && (!perfControlledByTimer)) {
hwCycles->start();
}
ioctlRun();
runTimer->disarm();
if (!perfControlledByTimer)
hwCycles.stop();
if (usePerf && (!perfControlledByTimer)) {
hwCycles->stop();
}
// The control signal may have been delivered after we exited
// from KVM. It will be pending in that case since it is
@@ -771,7 +799,10 @@ BaseKvmCPU::kvmRun(Tick ticks)
const uint64_t hostCyclesExecuted(getHostCycles() - baseCycles);
const uint64_t simCyclesExecuted(hostCyclesExecuted * hostFactor);
const uint64_t instsExecuted(hwInstructions.read() - baseInstrs);
uint64_t instsExecuted = 0;
if (usePerf) {
instsExecuted = hwInstructions->read() - baseInstrs;
}
ticksExecuted = runTimer->ticksFromHostCycles(hostCyclesExecuted);
/* Update statistics */
@@ -1288,13 +1319,14 @@ BaseKvmCPU::setupCounters()
// We might be re-attaching counters due threads being
// re-initialised after fork.
if (hwCycles.attached())
hwCycles.detach();
if (usePerf) {
if (hwCycles->attached()) {
hwCycles->detach();
}
hwCycles.attach(cfgCycles,
0); // TID (0 => currentThread)
setupInstCounter();
hwCycles->attach(cfgCycles, 0); // TID (0 => currentThread)
setupInstCounter();
}
}
bool
@@ -1344,10 +1376,16 @@ BaseKvmCPU::setupInstStop()
void
BaseKvmCPU::setupInstCounter(uint64_t period)
{
// This function is for setting up instruction counter using perf
if (!usePerf) {
return;
}
// No need to do anything if we aren't attaching for the first
// time or the period isn't changing.
if (period == activeInstPeriod && hwInstructions.attached())
if (period == activeInstPeriod && hwInstructions->attached()) {
return;
}
PerfKvmCounterConfig cfgInstructions(PERF_TYPE_HARDWARE,
PERF_COUNT_HW_INSTRUCTIONS);
@@ -1366,15 +1404,15 @@ BaseKvmCPU::setupInstCounter(uint64_t period)
// We need to detach and re-attach the counter to reliably change
// sampling settings. See PerfKvmCounter::period() for details.
if (hwInstructions.attached())
hwInstructions.detach();
assert(hwCycles.attached());
hwInstructions.attach(cfgInstructions,
if (hwInstructions->attached())
hwInstructions->detach();
assert(hwCycles->attached());
hwInstructions->attach(cfgInstructions,
0, // TID (0 => currentThread)
hwCycles);
*hwCycles);
if (period)
hwInstructions.enableSignals(KVM_KICK_SIGNAL);
hwInstructions->enableSignals(KVM_KICK_SIGNAL);
activeInstPeriod = period;
}

7
src/cpu/kvm/base.hh
View File

@@ -653,6 +653,9 @@ class BaseKvmCPU : public BaseCPU
*/
bool kvmStateDirty;
/** True if using perf; False otherwise*/
bool usePerf;
/** KVM internal ID of the vCPU */
long vcpuID;
@@ -763,7 +766,7 @@ class BaseKvmCPU : public BaseCPU
* PerfKvmTimer (see perfControlledByTimer) to trigger exits from
* KVM.
*/
PerfKvmCounter hwCycles;
std::unique_ptr<PerfKvmCounter> hwCycles;
/**
* Guest instruction counter.
@@ -776,7 +779,7 @@ class BaseKvmCPU : public BaseCPU
* @see setupInstBreak
* @see scheduleInstStop
*/
PerfKvmCounter hwInstructions;
std::unique_ptr<PerfKvmCounter> hwInstructions;
/**
* Does the runTimer control the performance counters?

16
src/cpu/kvm/perfevent.cc
View File

@@ -173,12 +173,20 @@ PerfKvmCounter::attach(PerfKvmCounterConfig &config,
{
if (errno == EACCES)
{
panic("PerfKvmCounter::attach recieved error EACCESS\n"
panic("PerfKvmCounter::attach received error EACCESS.\n"
" This error may be caused by a too restrictive setting\n"
" in the file '/proc/sys/kernel/perf_event_paranoid'\n"
" The default value was changed to 2 in kernel 4.6\n"
" in the file '/proc/sys/kernel/perf_event_paranoid'.\n"
" The default value was changed to 2 in kernel 4.6.\n"
" A value greater than 1 prevents gem5 from making\n"
" the syscall to perf_event_open");
" the syscall to perf_event_open.\n"
" Alternatively, you can set the usePerf flag of the KVM\n"
" CPU to False. Setting this flag to False will limit some\n"
" functionalities of KVM CPU, such as counting the number of\n"
" cycles and the number of instructions, as well as the\n"
" ability of exiting to gem5 after a certain amount of cycles\n"
" or instructions when using KVM CPU. An example can be found\n"
" here, configs/example/gem5_library/"
"x86-ubuntu-run-with-kvm-no-perf.py.");
}
panic("PerfKvmCounter::attach failed (%i)\n", errno);
}