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runtime: make time slice a const

A G will be preempted if it runs for 10ms without blocking. Currently
this constant is hard-coded in retake. Move it to a global const.
We'll use the time slice length in scheduling background GC.

Change-Id: I79a979948af2fad3afe5df9d4af4062f166554b7
Reviewed-on: https://go-review.googlesource.com/8838
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
This commit is contained in:
Austin Clements 2015-03-23 13:27:24 -04:00
parent 69001e404e
commit a23a341e10

View File

@ -2874,6 +2874,10 @@ var pdesc [_MaxGomaxprocs]struct {
syscallwhen int64
}
// forcePreemptNS is the time slice given to a G before it is
// preempted.
const forcePreemptNS = 10 * 1000 * 1000 // 10ms
func retake(now int64) uint32 {
n := 0
for i := int32(0); i < gomaxprocs; i++ {
@ -2913,14 +2917,14 @@ func retake(now int64) uint32 {
}
incidlelocked(1)
} else if s == _Prunning {
// Preempt G if it's running for more than 10ms.
// Preempt G if it's running for too long.
t := int64(_p_.schedtick)
if int64(pd.schedtick) != t {
pd.schedtick = uint32(t)
pd.schedwhen = now
continue
}
if pd.schedwhen+10*1000*1000 > now {
if pd.schedwhen+forcePreemptNS > now {
continue
}
preemptone(_p_)