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Avoid unnecessary (multi-core) writes of Thread::cur_time. #10164

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Avoid unnecessary (multi-core) writes of Thread::cur_time. #10164

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11 changes: 9 additions & 2 deletions iocore/eventsystem/I_Thread.h
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Original file line number Diff line number Diff line change
Expand Up @@ -175,7 +175,7 @@ class Thread
protected:
Thread();

static thread_local ink_hrtime cur_time;
static ink_hrtime cur_time;
};

extern Thread *this_thread();
Expand All @@ -189,5 +189,12 @@ Thread::get_hrtime()
TS_INLINE ink_hrtime
Thread::get_hrtime_updated()
{
return cur_time = ink_get_hrtime_internal();
ink_hrtime now = ink_get_hrtime_internal();
if (now > cur_time) {
// Thread::cur_time is used frequently in most threads. By avoiding unnecessary writes of it, locks of its cache line
// in (all) per-core caches are reduced. This should reduce CPU core stalls.
//
cur_time = now;
}
return cur_time;
}
2 changes: 1 addition & 1 deletion iocore/eventsystem/Thread.cc
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Expand Up @@ -34,7 +34,7 @@
// Common Interface impl //
///////////////////////////////////////////////

thread_local ink_hrtime Thread::cur_time = ink_get_hrtime_internal();
ink_hrtime Thread::cur_time = ink_get_hrtime_internal();
thread_local Thread *Thread::this_thread_ptr;

Thread::Thread()
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