diff options
Diffstat (limited to 'rts')
| -rw-r--r-- | rts/sm/Scav.c | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/rts/sm/Scav.c b/rts/sm/Scav.c index 39374c057f..2f61914e55 100644 --- a/rts/sm/Scav.c +++ b/rts/sm/Scav.c @@ -11,6 +11,37 @@ * * ---------------------------------------------------------------------------*/ +/* ---------------------------------------------------------------------------- + We have two main scavenge functions: + + - scavenge_block(bdescr *bd) + - scavenge_one(StgPtr p) + + As the names and parameters suggest, first one scavenges a whole block while + the second one only scavenges one object. This however is not the only + difference. scavenge_block scavenges all SRTs while scavenge_one only + scavenges SRTs of stacks. The reason is because scavenge_one is called in two + cases: + + - When scavenging a mut_list + - When scavenging a large object + + We don't have to scavenge SRTs when scavenging a mut_list, because we only + scavenge mut_lists in minor GCs, and static objects are only collected in + major GCs. + + However, because scavenge_one is also used to scavenge large objects (which + are scavenged even in major GCs), we need to deal with SRTs of large + objects. We never allocate large FUNs and THUNKs, but we allocate large + STACKs (e.g. in threadStackOverflow), and stack frames can have SRTs. So + scavenge_one skips FUN and THUNK SRTs but scavenges stack frame SRTs. + + In summary, in a major GC: + + - scavenge_block() scavenges all SRTs + - scavenge_one() scavenges only stack frame SRTs + ------------------------------------------------------------------------- */ + #include "PosixSource.h" #include "Rts.h" |