src/runtime/mgc0.go

// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package runtime

import _ "unsafe" // for go:linkname

//go:linkname runtime_debug_freeOSMemory runtime/debug.freeOSMemory
func runtime_debug_freeOSMemory() {
	gogc(2) // force GC and do eager sweep
	systemstack(scavenge_m)
}

var poolcleanup func()

//go:linkname sync_runtime_registerPoolCleanup sync.runtime_registerPoolCleanup
func sync_runtime_registerPoolCleanup(f func()) {
	poolcleanup = f
}

func clearpools() {
	// clear sync.Pools
	if poolcleanup != nil {
		poolcleanup()
	}

	for _, p := range &allp {
		if p == nil {
			break
		}
		// clear tinyalloc pool
		if c := p.mcache; c != nil {
			c.tiny = nil
			c.tinyoffset = 0

			// disconnect cached list before dropping it on the floor,
			// so that a dangling ref to one entry does not pin all of them.
			var sg, sgnext *sudog
			for sg = c.sudogcache; sg != nil; sg = sgnext {
				sgnext = sg.next
				sg.next = nil
			}
			c.sudogcache = nil
		}

		// clear defer pools
		for i := range p.deferpool {
			// disconnect cached list before dropping it on the floor,
			// so that a dangling ref to one entry does not pin all of them.
			var d, dlink *_defer
			for d = p.deferpool[i]; d != nil; d = dlink {
				dlink = d.link
				d.link = nil
			}
			p.deferpool[i] = nil
		}
	}
}

// backgroundgc is running in a goroutine and does the concurrent GC work.
// bggc holds the state of the backgroundgc.
func backgroundgc() {
	bggc.g = getg()
	bggc.g.issystem = true
	for {
		gcwork(0)
		lock(&bggc.lock)
		bggc.working = 0
		goparkunlock(&bggc.lock, "Concurrent GC wait", traceEvGoBlock)
	}
}

func bgsweep() {
	sweep.g = getg()
	getg().issystem = true
	for {
		for gosweepone() != ^uintptr(0) {
			sweep.nbgsweep++
			Gosched()
		}
		lock(&gclock)
		if !gosweepdone() {
			// This can happen if a GC runs between
			// gosweepone returning ^0 above
			// and the lock being acquired.
			unlock(&gclock)
			continue
		}
		sweep.parked = true
		goparkunlock(&gclock, "GC sweep wait", traceEvGoBlock)
	}
}