Skip to content

8318709: Improve System.nanoTime performance on Windows #16336

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
djelinski wants to merge 2 commits into from
Closed

8318709: Improve System.nanoTime performance on Windows #16336

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
50bf0dd
Improve nanoTime performance
djelinski Oct 24, 2023
4ba32be
Fix variable name
djelinski Oct 26, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
22 changes: 7 additions & 15 deletions src/hotspot/os/windows/os_windows.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -801,20 +801,12 @@ void os::free_thread(OSThread* osthread) {
static jlong first_filetime;
static jlong initial_performance_count;
static jlong performance_frequency;


jlong as_long(LARGE_INTEGER x) {
jlong result = 0; // initialization to avoid warning
set_high(&result, x.HighPart);
set_low(&result, x.LowPart);
return result;
}

static double nanos_per_count; // NANOSECS_PER_SEC / performance_frequency

jlong os::elapsed_counter() {
LARGE_INTEGER count;
QueryPerformanceCounter(&count);
return as_long(count) - initial_performance_count;
return count.QuadPart - initial_performance_count;
}


Expand Down Expand Up @@ -978,9 +970,10 @@ void os::set_native_thread_name(const char *name) {
void os::win32::initialize_performance_counter() {
LARGE_INTEGER count;
QueryPerformanceFrequency(&count);
performance_frequency = as_long(count);
performance_frequency = count.QuadPart;
nanos_per_count = NANOSECS_PER_SEC / (double)performance_frequency;
QueryPerformanceCounter(&count);
initial_performance_count = as_long(count);
initial_performance_count = count.QuadPart;
}


Expand Down Expand Up @@ -1082,9 +1075,8 @@ void os::javaTimeSystemUTC(jlong &seconds, jlong &nanos) {
jlong os::javaTimeNanos() {
LARGE_INTEGER current_count;
QueryPerformanceCounter(&current_count);
double current = as_long(current_count);
double freq = performance_frequency;
jlong time = (jlong)((current/freq) * NANOSECS_PER_SEC);
double current = current_count.QuadPart;
jlong time = (jlong)(current * nanos_per_count);
return time;
}

Expand Down