e0c3d85f08
Currently, in accordance with the GC pacing proposal, we schedule background marking with a goal of achieving 25% utilization *total* between mutator assists and background marking. This is stricter than was set out in the Go 1.5 proposal, which suggests that the garbage collector can use 25% just for itself and anything the mutator does to help out is on top of that. It also has several technical drawbacks. Because mutator assist time is constantly changing and we can't have instantaneous information on background marking time, it effectively requires hitting a moving target based on out-of-date information. This works out in the long run, but works poorly for short GC cycles and on short time scales. Also, this requires time-multiplexing all Ps between the mutator and background GC since the goal utilization of background GC constantly fluctuates. This results in a complicated scheduling algorithm, poor affinity, and extra overheads from context switching. This change modifies the way we schedule and run background marking so that background marking always consumes 25% of GOMAXPROCS and mutator assist is in addition to this. This enables a much more robust scheduling algorithm where we pre-determine the number of Ps we should dedicate to background marking as well as the utilization goal for a single floating "remainder" mark worker. Change-Id: I187fa4c03ab6fe78012a84d95975167299eb9168 Reviewed-on: https://go-review.googlesource.com/9013 Reviewed-by: Rick Hudson <rlh@golang.org> |
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