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More closely duplicating the allocation policy from the old vmarena, and documenting why.

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Copied from Perforce
 Change: 184601
 ServerID: perforce.ravenbrook.com
This commit is contained in:
Richard Brooksby 2014-02-28 13:35:51 +00:00
parent 4eec2493b7
commit 53bdfaab23
1 changed files with 7 additions and 9 deletions
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16
mps/code/arena.c
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@ -904,6 +904,10 @@ failMark:
* This is the code responsible for making decisions about where to allocate
* memory. Avoid distributing code for doing this elsewhere, so that policy
* can be maintained and adjusted.
*
* TODO: This currently duplicates the policy from VMAllocPolicy in
* //info.ravenbrook.com/project/mps/master/code/arenavm.c#36 in order
* to avoid disruption to clients, but needs revision.
*/
static Res arenaAllocPolicy(Tract *tractReturn, Arena arena, SegPref pref,
@ -918,8 +922,6 @@ static Res arenaAllocPolicy(Tract *tractReturn, Arena arena, SegPref pref,
AVER(size > (Size)0);
AVERT(Pool, pool);
/* FIXME: Allow arena to take an option to ignore zones. */
/* Don't attempt to allocate if doing so would definitely exceed the
commit limit. */
if (arena->spareCommitted < size) {
@ -930,11 +932,8 @@ static Res arenaAllocPolicy(Tract *tractReturn, Arena arena, SegPref pref,
}
}
/* FIXME: Think about this. We may have barged into a blacklisted zone. */
AVER(ZoneSetInter(pref->zones, pref->avoid) == ZoneSetEMPTY);
/* Plan A: allocate from the free CBS in the requested zones */
zones = pref->zones;
zones = ZoneSetDiff(pref->zones, pref->avoid);
if (zones != ZoneSetEMPTY) {
res = arenaAllocFromCBS(&tract, zones, pref->high, size, pool);
if (res == ResOK)
@ -945,7 +944,7 @@ static Res arenaAllocPolicy(Tract *tractReturn, Arena arena, SegPref pref,
/* TODO: Pools without ambiguous roots might not care about the blacklist. */
/* TODO: zones are precious and (currently) never deallocated, so we
should consider extending the arena first if address space is plentiful */
moreZones = ZoneSetUnion(zones, ZoneSetDiff(arena->freeZones, pref->avoid));
moreZones = ZoneSetUnion(pref->zones, ZoneSetDiff(arena->freeZones, pref->avoid));
if (moreZones != zones) {
res = arenaAllocFromCBS(&tract, moreZones, pref->high, size, pool);
if (res == ResOK)
@ -957,7 +956,6 @@ static Res arenaAllocPolicy(Tract *tractReturn, Arena arena, SegPref pref,
res = arena->class->grow(arena, pref, size);
if (res != ResOK)
return res;
zones = pref->zones;
if (zones != ZoneSetEMPTY) {
res = arenaAllocFromCBS(&tract, zones, pref->high, size, pool);
if (res == ResOK)
@ -975,7 +973,7 @@ static Res arenaAllocPolicy(Tract *tractReturn, Arena arena, SegPref pref,
objects with those from other generations, causing the zone check
to give false positives and slowing down the collector. */
/* TODO: log an event for this */
evenMoreZones = ZoneSetUnion(moreZones, ZoneSetDiff(ZoneSetUNIV, pref->avoid));
evenMoreZones = ZoneSetDiff(ZoneSetUNIV, pref->avoid);
if (evenMoreZones != moreZones) {
res = arenaAllocFromCBS(&tract, evenMoreZones, pref->high, size, pool);
if (res == ResOK)