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8214180: Need better granularity for sleeping

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Reviewed-by: eosterlund, dcubed, dholmes
This commit is contained in:
Robbin Ehn 2018-12-20 10:05:19 +01:00
parent 595fcb59bc
commit 994ab71870
9 changed files with 71 additions and 74 deletions
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37
src/hotspot/os/linux/os_linux.cpp
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@ -4033,33 +4033,6 @@ size_t os::read_at(int fd, void *buf, unsigned int nBytes, jlong offset) {
return ::pread(fd, buf, nBytes, offset);
}
// Short sleep, direct OS call.
//
// Note: certain versions of Linux CFS scheduler (since 2.6.23) do not guarantee
// sched_yield(2) will actually give up the CPU:
//
// * Alone on this pariticular CPU, keeps running.
// * Before the introduction of "skip_buddy" with "compat_yield" disabled
// (pre 2.6.39).
//
// So calling this with 0 is an alternative.
//
void os::naked_short_sleep(jlong ms) {
struct timespec req;
assert(ms < 1000, "Un-interruptable sleep, short time use only");
req.tv_sec = 0;
if (ms > 0) {
req.tv_nsec = (ms % 1000) * 1000000;
} else {
req.tv_nsec = 1;
}
nanosleep(&req, NULL);
return;
}
// Sleep forever; naked call to OS-specific sleep; use with CAUTION
void os::infinite_sleep() {
while (true) { // sleep forever ...
@ -4072,6 +4045,16 @@ bool os::dont_yield() {
return DontYieldALot;
}
// Linux CFS scheduler (since 2.6.23) does not guarantee sched_yield(2) will
// actually give up the CPU. Since skip buddy (v2.6.28):
//
// * Sets the yielding task as skip buddy for current CPU's run queue.
// * Picks next from run queue, if empty, picks a skip buddy (can be the yielding task).
// * Clears skip buddies for this run queue (yielding task no longer a skip buddy).
//
// An alternative is calling os::naked_short_nanosleep with a small number to avoid
// getting re-scheduled immediately.
//
void os::naked_yield() {
sched_yield();
}