diff options
Diffstat (limited to 'examples/vm_power_manager/oob_monitor_x86.c')
| -rw-r--r-- | examples/vm_power_manager/oob_monitor_x86.c | 23 |
1 files changed, 18 insertions, 5 deletions
diff --git a/examples/vm_power_manager/oob_monitor_x86.c b/examples/vm_power_manager/oob_monitor_x86.c index 589c604e..ebd96b20 100644 --- a/examples/vm_power_manager/oob_monitor_x86.c +++ b/examples/vm_power_manager/oob_monitor_x86.c @@ -33,10 +33,10 @@ static float apply_policy(int core) { struct core_info *ci; - uint64_t counter; + uint64_t counter = 0; uint64_t branches, branch_misses; - uint32_t last_branches, last_branch_misses; - int hits_diff, miss_diff; + uint64_t last_branches, last_branch_misses; + int64_t hits_diff, miss_diff; float ratio; int ret; @@ -54,6 +54,7 @@ apply_policy(int core) core); branches = counter; + counter = 0; ret = pread(ci->cd[core].msr_fd, &counter, sizeof(counter), IA32_PERFCTR1); if (ret < 0) @@ -66,13 +67,25 @@ apply_policy(int core) ci->cd[core].last_branches = branches; ci->cd[core].last_branch_misses = branch_misses; - hits_diff = (int)branches - (int)last_branches; + /* + * Intentional right shift to make MSB 0 to avoid + * possible signed overflow or truncation. + */ + branches >>= 1; + last_branches >>= 1; + hits_diff = (int64_t)branches - (int64_t)last_branches; if (hits_diff <= 0) { /* Likely a counter overflow condition, skip this round */ return -1.0; } - miss_diff = (int)branch_misses - (int)last_branch_misses; + /* + * Intentional right shift to make MSB 0 to avoid + * possible signed overflow or truncation. + */ + branch_misses >>= 1; + last_branch_misses >>= 1; + miss_diff = (int64_t)branch_misses - (int64_t)last_branch_misses; if (miss_diff <= 0) { /* Likely a counter overflow condition, skip this round */ return -1.0; |