ARM: Detect and skip udelay() functions in linux kernel.

This change speeds up booting, especially in MP cases, by not executing
udelay() on the core but instead skipping ahead tha amount of time that is being
delayed.

diff --git a/src/arch/arm/linux/system.cc b/src/arch/arm/linux/system.cc
index 38024c0588d644702cac6672ed135138156bc8c9..7aff2b6ef2e3a9fee1660120497d3a2de028b3a8 100644 (file)
--- a/src/arch/arm/linux/system.cc
+++ b/src/arch/arm/linux/system.cc
@@ -47,9 +47,11 @@
 #include "base/loader/object_file.hh"
 #include "base/loader/symtab.hh"
 #include "cpu/thread_context.hh"
+#include "kern/linux/events.hh"
 #include "mem/physical.hh"
 
 using namespace ArmISA;
+using namespace Linux;
 
 LinuxArmSystem::LinuxArmSystem(Params *p)
     : ArmSystem(p)
@@ -96,6 +98,24 @@ LinuxArmSystem::LinuxArmSystem(Params *p)
     if (!kernelPanicEvent)
         panic("could not find kernel symbol \'panic\'");
 #endif
+
+    // With ARM udelay() is #defined to __udelay
+    Addr addr = 0;
+    if (kernelSymtab->findAddress("__udelay", addr)) {
+        uDelaySkipEvent = new UDelayEvent(&pcEventQueue, "__udelay",
+                fixFuncEventAddr(addr), 1000, 0);
+    } else {
+        panic("couldn't find kernel symbol \'udelay\'");
+    }
+
+    // constant arguments to udelay() have some precomputation done ahead of
+    // time. Constant comes from code.
+    if (kernelSymtab->findAddress("__const_udelay", addr)) {
+        constUDelaySkipEvent = new UDelayEvent(&pcEventQueue, "__const_udelay",
+                fixFuncEventAddr(addr), 1000, 107374);
+    } else {
+        panic("couldn't find kernel symbol \'udelay\'");
+    }
 }
 
 void
@@ -115,6 +135,10 @@ LinuxArmSystem::initState()
 
 LinuxArmSystem::~LinuxArmSystem()
 {
+    if (uDelaySkipEvent)
+        delete uDelaySkipEvent;
+    if (constUDelaySkipEvent)
+        delete constUDelaySkipEvent;
 }
 
 LinuxArmSystem *

diff --git a/src/arch/arm/linux/system.hh b/src/arch/arm/linux/system.hh
index 4e5ebcd7353292c292fc8b462e915e0d9296f8b1..2ef65fea28aad97b4e2da3b92d72a4d1fb42d967 100644 (file)
--- a/src/arch/arm/linux/system.hh
+++ b/src/arch/arm/linux/system.hh
@@ -74,6 +74,19 @@ class LinuxArmSystem : public ArmSystem
     /** Event to halt the simulator if the kernel calls panic()  */
     BreakPCEvent *kernelPanicEvent;
 #endif
+    /**
+     * PC based event to skip udelay(<time>) calls and quiesce the
+     * processor for the appropriate amount of time. This is not functionally
+     * required but does speed up simulation.
+     */
+    Linux::UDelayEvent *uDelaySkipEvent;
+
+    /** Another PC based skip event for const_udelay(). Similar to the udelay
+     * skip, but this function precomputes the first multiply that is done
+     * in the generic case since the parameter is known at compile time.
+     * Thus we need to do some division to get back to us.
+     */
+    Linux::UDelayEvent *constUDelaySkipEvent;
 };
 
 #endif // __ARCH_ARM_LINUX_SYSTEM_HH__

diff --git a/src/cpu/simple/atomic.cc b/src/cpu/simple/atomic.cc
index 27635d3ce680c395a0eb7f95cd51fbd41c3fc254..6aa0eb64e8e154f657f62afd17e1e36fe3fd29ad 100644 (file)
--- a/src/cpu/simple/atomic.cc
+++ b/src/cpu/simple/atomic.cc
@@ -641,6 +641,9 @@ AtomicSimpleCPU::tick()
             checkForInterrupts();
 
         checkPcEventQueue();
+        // We must have just got suspended by a PC event
+        if (_status == Idle)
+            return;
 
         Fault fault = NoFault;
 

diff --git a/src/cpu/simple/timing.cc b/src/cpu/simple/timing.cc
index 632e83356d128ac8903e508426803efc9a4161ea..aca48e5d4550edce98d5f39123fc5ac603f02da3 100644 (file)
--- a/src/cpu/simple/timing.cc
+++ b/src/cpu/simple/timing.cc
@@ -714,6 +714,10 @@ TimingSimpleCPU::fetch()
 
     checkPcEventQueue();
 
+    // We must have just got suspended by a PC event
+    if (_status == Idle)
+        return;
+
     TheISA::PCState pcState = thread->pcState();
     bool needToFetch = !isRomMicroPC(pcState.microPC()) && !curMacroStaticInst;
 

diff --git a/src/kern/linux/events.cc b/src/kern/linux/events.cc
index 60aa857acac8cafb832910ebd2338614ea1a0378..75c2b6f7f39c2a3cbd77b623ec3fe49c1fa1451f 100644 (file)
--- a/src/kern/linux/events.cc
+++ b/src/kern/linux/events.cc
@@ -44,11 +44,13 @@
 #include <sstream>
 
 #include "base/trace.hh"
+#include "arch/utility.hh"
 #include "cpu/thread_context.hh"
 #include "kern/linux/events.hh"
 #include "kern/linux/printk.hh"
 #include "kern/system_events.hh"
 #include "sim/arguments.hh"
+#include "sim/pseudo_inst.hh"
 #include "sim/system.hh"
 
 namespace Linux {
@@ -66,4 +68,27 @@ DebugPrintkEvent::process(ThreadContext *tc)
     SkipFuncEvent::process(tc);
 }
 
+void
+UDelayEvent::process(ThreadContext *tc)
+{
+    int arg_num  = 0;
+
+    // Get the time in native size
+    uint64_t time = TheISA::getArgument(tc, arg_num,  (uint16_t)-1, false);
+
+    // convert parameter to ns
+    if (argDivToNs)
+        time /= argDivToNs;
+
+    time *= argMultToNs;
+
+    // Convert ns to ticks
+    time *= SimClock::Int::ns;
+
+    SkipFuncEvent::process(tc);
+
+    PseudoInst::quiesceNs(tc, time);
+}
+
+
 } // namespace linux

diff --git a/src/kern/linux/events.hh b/src/kern/linux/events.hh
index e36a72ddea2051177f3fc9488cf6fd54a37119b0..3f5f2526f422c8f7272419713cd831da8274d16e 100644 (file)
--- a/src/kern/linux/events.hh
+++ b/src/kern/linux/events.hh
@@ -44,6 +44,33 @@ class DebugPrintkEvent : public SkipFuncEvent
     virtual void process(ThreadContext *xc);
 };
 
+/** A class to skip udelay() and related calls in the kernel.
+ * This class has two additional parameters that take the argument to udelay and
+ * manipulated it to come up with ns and eventually ticks to quiesce for.
+ * See descriptions of argDivToNs and argMultToNs below.
+ */
+class UDelayEvent : public SkipFuncEvent
+{
+  private:
+    /** value to divide arg by to create ns. This is present beacues the linux
+     * kernel code sometime precomputes the first multiply that is done in
+     * udelay() if the parameter is a constant. We need to undo it so here is
+     * how. */
+    uint64_t argDivToNs;
+
+    /** value to multiple arg by to create ns. Nominally, this is 1000 to
+     * convert us to ns, but since linux can do some preprocessing of constant
+     * values something else might be required. */
+    uint64_t argMultToNs;
+
+  public:
+    UDelayEvent(PCEventQueue *q, const std::string &desc, Addr addr,
+            uint64_t mult, uint64_t div)
+        : SkipFuncEvent(q, desc, addr), argDivToNs(div), argMultToNs(mult) {}
+    virtual void process(ThreadContext *xc);
+};
+
+
 }
 
 #endif