Adds a stopwatch to JIT to allow precise time measurements by instrum…

…entation. (#197)
solana-labs · Jul 13, 2021 · 38ba6a5 · 38ba6a5
1 parent 134c217
commit 38ba6a5
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Showing 2 changed files with 79 additions and 3 deletions.
diff --git a/src/jit.rs b/src/jit.rs
@@ -342,14 +342,39 @@ enum EnvironmentStackSlot {
     PrevInsnMeter = 8,
     /// Constant pointer to instruction_meter
     InsnMeterPtr = 9,
+    /// CPU cycles accumulated by the stop watch
+    StopwatchNumerator = 10,
+    /// Number of times the stop watch was used
+    StopwatchDenominator = 11,
     /// Bumper for size_of
-    SlotCount = 10,
+    SlotCount = 12,
 }
 
 fn slot_on_environment_stack(jit: &JitCompiler, slot: EnvironmentStackSlot) -> i32 {
     -8 * (slot as i32 + jit.environment_stack_key)
 }
 
+#[allow(dead_code)]
+#[inline]
+fn emit_stopwatch<E: UserDefinedError>(jit: &mut JitCompiler, begin: bool) -> Result<(), EbpfError<E>> {
+    jit.stopwatch_is_active = true;
+    X86Instruction::push(RDX).emit(jit)?;
+    X86Instruction::push(RAX).emit(jit)?;
+    X86Instruction::fence(FenceType::Load).emit(jit)?; // lfence
+    X86Instruction::cycle_count().emit(jit)?; // rdtsc
+    X86Instruction::fence(FenceType::Load).emit(jit)?; // lfence
+    emit_alu(jit, OperandSize::S64, 0xc1, 4, RDX, 32, None)?; // RDX <<= 32;
+    emit_alu(jit, OperandSize::S64, 0x09, RDX, RAX, 0, None)?; // RAX |= RDX;
+    if begin {
+        emit_alu(jit, OperandSize::S64, 0x29, RAX, RBP, 0, Some(X86IndirectAccess::Offset(slot_on_environment_stack(jit, EnvironmentStackSlot::StopwatchNumerator))))?; // *numerator -= RAX;
+    } else {
+        emit_alu(jit, OperandSize::S64, 0x01, RAX, RBP, 0, Some(X86IndirectAccess::Offset(slot_on_environment_stack(jit, EnvironmentStackSlot::StopwatchNumerator))))?; // *numerator += RAX;
+        emit_alu(jit, OperandSize::S64, 0x81, 0, RBP, 1, Some(X86IndirectAccess::Offset(slot_on_environment_stack(jit, EnvironmentStackSlot::StopwatchDenominator))))?; // *denominator += 1;
+    }
+    X86Instruction::pop(RAX).emit(jit)?;
+    X86Instruction::pop(RDX).emit(jit)
+}
+
 /* Explaination of the Instruction Meter
 
     The instruction meter serves two purposes: First, measure how many BPF instructions are
@@ -869,6 +894,7 @@ pub struct JitCompiler {
     handler_anchors: HashMap<usize, usize>,
     config: Config,
     rng: ThreadRng,
+    stopwatch_is_active: bool,
     environment_stack_key: i32,
     program_argument_key: i32,
 }
@@ -948,6 +974,7 @@ impl JitCompiler {
             handler_anchors: HashMap::new(),
             config: *_config,
             rng,
+            stopwatch_is_active: false,
             environment_stack_key,
             program_argument_key,
         })
@@ -1496,6 +1523,11 @@ impl JitCompiler {
         // Save instruction meter
         X86Instruction::push(ARGUMENT_REGISTERS[3]).emit(self)?;
 
+        // Initialize stop watch
+        emit_alu(self, OperandSize::S64, 0x31, R11, R11, 0, None)?; // R11 ^= R11; 
+        X86Instruction::push(R11).emit(self)?;
+        X86Instruction::push(R11).emit(self)?;
+
         // Initialize frame pointer
         X86Instruction::mov(OperandSize::S64, RSP, RBP).emit(self)?;
         emit_alu(self, OperandSize::S64, 0x81, 0, RBP, 8 * (EnvironmentStackSlot::SlotCount as i64 - 1 + self.environment_stack_key as i64), None)?;
@@ -1524,6 +1556,17 @@ impl JitCompiler {
         // Epilogue
         set_anchor(self, TARGET_PC_EPILOGUE);
 
+        // Print stop watch value
+        fn stopwatch_result(numerator: u64, denominator: u64) {
+            println!("Stop watch: {} / {} = {}", numerator, denominator, if denominator == 0 { 0.0 } else { numerator as f64 / denominator as f64 });
+        }
+        if self.stopwatch_is_active {
+            emit_rust_call(self, stopwatch_result as *const u8, &[
+                Argument { index: 1, value: Value::RegisterIndirect(RBP, slot_on_environment_stack(self, EnvironmentStackSlot::StopwatchDenominator), false) },
+                Argument { index: 0, value: Value::RegisterIndirect(RBP, slot_on_environment_stack(self, EnvironmentStackSlot::StopwatchNumerator), false) },
+            ], None, false)?;
+        }
+
         // Store instruction_meter in RAX
         X86Instruction::mov(OperandSize::S64, ARGUMENT_REGISTERS[0], RAX).emit(self)?;
 

diff --git a/src/x86.rs b/src/x86.rs
@@ -50,10 +50,20 @@ pub enum X86IndirectAccess {
     /// [second_operand + offset]
     Offset(i32),
     /// [second_operand + offset + index << shift]
-    #[allow(dead_code)]
     OffsetIndexShift(i32, u8, u8),
 }
 
+#[allow(dead_code)]
+#[derive(PartialEq, Eq, Copy, Clone)]
+pub enum FenceType {
+    /// lfence
+    Load = 5,
+    /// mfence
+    All = 6,
+    /// sfence
+    Store = 7,
+}
+
 #[derive(PartialEq, Eq, Copy, Clone)]
 pub struct X86Instruction {
     pub size: OperandSize,
@@ -288,7 +298,6 @@ impl X86Instruction {
     }
 
     /// Load effective address of source into destination
-    #[allow(dead_code)]
     pub fn lea(
         size: OperandSize,
         source: u8,
@@ -490,4 +499,28 @@ impl X86Instruction {
             }
         }
     }
+
+    /// rdtsc
+    #[allow(dead_code)]
+    pub fn cycle_count() -> Self {
+        Self {
+            size: OperandSize::S32,
+            opcode_escape_sequence: 1,
+            opcode: 0x31,
+            modrm: false,
+            ..Self::default()
+        }
+    }
+
+    /// lfence / sfence / mfence
+    #[allow(dead_code)]
+    pub fn fence(fence_type: FenceType) -> Self {
+        Self {
+            size: OperandSize::S32,
+            opcode_escape_sequence: 1,
+            opcode: 0xae,
+            first_operand: fence_type as u8,
+            ..Self::default()
+        }
+    }
 }