github.com/shogo82148/std@v1.22.1-0.20240327122250-4e474527810c/runtime/mgcsweep.go (about)

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Garbage collector: sweeping
     6  
     7  // The sweeper consists of two different algorithms:
     8  //
     9  // * The object reclaimer finds and frees unmarked slots in spans. It
    10  //   can free a whole span if none of the objects are marked, but that
    11  //   isn't its goal. This can be driven either synchronously by
    12  //   mcentral.cacheSpan for mcentral spans, or asynchronously by
    13  //   sweepone, which looks at all the mcentral lists.
    14  //
    15  // * The span reclaimer looks for spans that contain no marked objects
    16  //   and frees whole spans. This is a separate algorithm because
    17  //   freeing whole spans is the hardest task for the object reclaimer,
    18  //   but is critical when allocating new spans. The entry point for
    19  //   this is mheap_.reclaim and it's driven by a sequential scan of
    20  //   the page marks bitmap in the heap arenas.
    21  //
    22  // Both algorithms ultimately call mspan.sweep, which sweeps a single
    23  // heap span.
    24  
    25  package runtime