Merge branch 'elementary-computer-science'

Makefile

@@ -52,7 +52,7 @@ selfie-gc-nomain.h: selfie-gc.h
 # Consider these targets as targets, not files
 .PHONY: self self-self self-self-check 64-to-32-bit \
  whitespace quine escape debug replay \
- emu emu-emu emu-emu-emu emu-vmm-emu os-emu os-vmm-emu \
+ emu emu-emu emu-emu-emu emu-vmm-emu os-emu os-vmm-emu overhead \
  self-emu self-os-emu self-os-vmm-emu min mob \
  gib gclib giblib gclibtest boehmgc cache \
  sat brr bzz mon smt beat btor2 all
@@ -133,6 +133,10 @@ os-emu: selfie selfie.m
 os-vmm-emu: selfie selfie.m
  ./selfie -l selfie.m -m 3 -l selfie.m -y 2 -l selfie.m -y 1
 
+# Determine overhead of timer interrupts and context switching
+overhead: selfie selfie.m
+ ./selfie -l selfie.m -m 2 -l selfie.m -c examples/overhead.c -y 1
+
 # Self-compile on emulator
 self-emu: selfie selfie.m selfie.s
  ./selfie -l selfie.m -m 3 -c selfie.c -o selfie-emu.m -s selfie-emu.s

examples/overhead.c

@@ -0,0 +1,10 @@
+// looping for measuring overhead of timer interrupts
+// as upper bound on overhead of context switching
+uint64_t main() {
+ uint64_t i;
+
+ i = 0;
+
+ while (i < 1000000000)
+ i = i + 1;
+}

selfie.c

@@ -10721,10 +10721,12 @@ void print_instruction_versus_exception_profile(uint64_t* parent_context) {
  uint64_t ec_count;
  uint64_t* context;
 
- printf("%s: %lu(%lu.%.2lu%%) executed instructions", selfie_name,
+ printf("%s: %lu executed instructions [%lu.%.2lu%% share, factor %lu.%.2lu]\n", selfie_name,
  get_ic_all(parent_context),
  percentage_format_integral_2(get_total_number_of_instructions(), get_ic_all(parent_context)),
- percentage_format_fractional_2(get_total_number_of_instructions(), get_ic_all(parent_context)));
+ percentage_format_fractional_2(get_total_number_of_instructions(), get_ic_all(parent_context)),
+ ratio_format_integral_2(get_total_number_of_instructions(), get_ic_all(parent_context)),
+ ratio_format_fractional_2(get_total_number_of_instructions(), get_ic_all(parent_context)));
 
  ic_count = 0;
  ec_count = 0;
@@ -10741,17 +10743,15 @@ void print_instruction_versus_exception_profile(uint64_t* parent_context) {
  context = get_next_context(context);
  }
 
- if (ec_count > 0) {
+ if (ec_count > 0)
  // assert: get_ic_all(parent_context) > 0
- printf(" [%lu.%.2lu%% overhead, factor %lu.%.2lu]\n",
+ printf("%s: %lu exceptions handled by %lu instructions each [%lu.%.2lu%% overhead, factor %lu.%.2lu]\n", selfie_name,
+ ec_count,
+ ratio_format_integral_2(get_ic_all(parent_context), ec_count),
  percentage_format_integral_2(ic_count, get_ic_all(parent_context)),
  percentage_format_fractional_2(ic_count, get_ic_all(parent_context)),
  ratio_format_integral_2(get_ic_all(parent_context), ic_count) + 1,
  ratio_format_fractional_2(get_ic_all(parent_context), ic_count));
- printf("%s: %lu instructions per exception, handling %lu exceptions in total", selfie_name,
- ec_count, ratio_format_integral_2(get_ic_all(parent_context), ec_count));
- }
- println();
 }
 
 void print_profile() {