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authorAlex Bennée <alex.bennee@linaro.org>2017-03-31 16:09:42 +0100
committerAlex Bennée <alex.bennee@linaro.org>2017-04-10 10:23:38 +0100
commite4cd96571f00e290e93dcc65a6d2b616b159dea6 (patch)
tree7b12718e50c75b70845d8b31463793af1cb67874
parent05248382251a58a14da60a640d29f570524174d3 (diff)
cpus: don't credit executed instructions before they have run
Outside of the vCPU thread icount time will only be tracked against timers_state.qemu_icount. We no longer credit cycles until they have completed the run. Inside the vCPU thread we adjust for passage of time by looking at how many have run so far. This is only valid inside the vCPU thread while it is running. Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
-rw-r--r--cpus.c25
-rw-r--r--include/qom/cpu.h1
2 files changed, 20 insertions, 6 deletions
diff --git a/cpus.c b/cpus.c
index 6034b104c3..0ecb0b87f0 100644
--- a/cpus.c
+++ b/cpus.c
@@ -223,6 +223,15 @@ void qemu_tcg_configure(QemuOpts *opts, Error **errp)
}
}
+/* The current number of executed instructions is based on what we
+ * originally budgeted minus the current state of the decrementing
+ * icount counters in extra/u16.low.
+ */
+static int64_t cpu_get_icount_executed(CPUState *cpu)
+{
+ return cpu->icount_budget - (cpu->icount_decr.u16.low + cpu->icount_extra);
+}
+
int64_t cpu_get_icount_raw(void)
{
int64_t icount;
@@ -234,7 +243,8 @@ int64_t cpu_get_icount_raw(void)
fprintf(stderr, "Bad icount read\n");
exit(1);
}
- icount -= (cpu->icount_decr.u16.low + cpu->icount_extra);
+ /* Take into account what has run */
+ icount += cpu_get_icount_executed(cpu);
}
return icount;
}
@@ -1195,7 +1205,10 @@ static void prepare_icount_for_run(CPUState *cpu)
count = tcg_get_icount_limit();
- timers_state.qemu_icount += count;
+ /* To calculate what we have executed so far we need to know
+ * what we originally budgeted to run this cycle */
+ cpu->icount_budget = count;
+
decr = (count > 0xffff) ? 0xffff : count;
count -= decr;
cpu->icount_decr.u16.low = decr;
@@ -1206,14 +1219,14 @@ static void prepare_icount_for_run(CPUState *cpu)
static void process_icount_data(CPUState *cpu)
{
if (use_icount) {
- /* Fold pending instructions back into the
- instruction counter, and clear the interrupt flag. */
- timers_state.qemu_icount -= (cpu->icount_decr.u16.low
- + cpu->icount_extra);
+ /* Account for executed instructions */
+ timers_state.qemu_icount += cpu_get_icount_executed(cpu);
/* Reset the counters */
cpu->icount_decr.u16.low = 0;
cpu->icount_extra = 0;
+ cpu->icount_budget = 0;
+
replay_account_executed_instructions();
}
}
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index c3292efe1c..5d10359c8f 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -332,6 +332,7 @@ struct CPUState {
/* updates protected by BQL */
uint32_t interrupt_request;
int singlestep_enabled;
+ int64_t icount_budget;
int64_t icount_extra;
sigjmp_buf jmp_env;