• Austin Clements's avatar
    runtime: drain local runq when dedicated mark worker runs · 489620d8
    Austin Clements authored
    When the dedicated mark worker runs, the scheduler won't run on that P
    again until GC runs out of mark work. As a result, any goroutines in
    that P's local run queue are stranded until another P steals them. In
    a normally operating system this may take a long time, and in a 100%
    busy system, the scheduler never attempts to steal from another P.
    
    Fix this by draining the local run queue into the global run queue if
    the dedicated mark worker has run for long enough. We don't do this
    immediately upon scheduling the dedicated mark worker in order to
    avoid destroying locality if the mark worker runs for a short time.
    Instead, the scheduler delays draining the run queue until the mark
    worker gets its first preemption request (and otherwise ignores the
    preemption request).
    
    Fixes #20011.
    
    Change-Id: I13067194b2f062b8bdef25cb75e4143b7fb6bb73
    Reviewed-on: https://go-review.googlesource.com/46610
    Run-TryBot: Austin Clements <austin@google.com>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarRick Hudson <rlh@golang.org>
    489620d8
mgc.go 71.1 KB