• Russ Cox's avatar
    runtime: use 2-bit heap bitmap (in place of 4-bit) · 0234dfd4
    Russ Cox authored
    Previous CLs changed the representation of the non-heap type bitmaps
    to be 1-bit bitmaps (pointer or not). Before this CL, the heap bitmap
    stored a 2-bit type for each word and a mark bit and checkmark bit
    for the first word of the object. (There used to be additional per-word bits.)
    
    Reduce heap bitmap to 2-bit, with 1 dedicated to pointer or not,
    and the other used for mark, checkmark, and "keep scanning forward
    to find pointers in this object." See comments for details.
    
    This CL replaces heapBitsSetType with very slow but obviously correct code.
    A followup CL will optimize it. (Spoiler: the new code is faster than Go 1.4 was.)
    
    Change-Id: I999577a133f3cfecacebdec9cdc3573c235c7fb9
    Reviewed-on: https://go-review.googlesource.com/9703Reviewed-by: 's avatarRick Hudson <rlh@golang.org>
    Reviewed-by: 's avatarAustin Clements <austin@google.com>
    0234dfd4
heapdump.go 18.3 KB