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* Introduced new area creation flag CREATE_AREA_DONT_COMMIT_MEMORY.

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map_backing_store() doesn't commit memory when this flag is given.
* Used the new flag vm_copy_area(): We no longer commit memory for read-only
  areas. This prevents read-only mapped files from suddenly requiring memory
  after fork(). Might improve the situation on machines with very little RAM
  a bit.
  We should probably mark writable copies over-committing, since the usual
  case is fork() + exec() where the child normally doesn't need more than a
  few pages until calling exec(). That would significantly reduce the memory
  requirement for jamming the Haiku tree.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@36651 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Ingo Weinhold 2010-05-06 14:59:14 +00:00
parent d55567bbf9
commit 13fa4c845a
2 changed files with 7 additions and 4 deletions
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1
headers/private/kernel/vm/vm.h
View File

@ -32,6 +32,7 @@ struct VMPageWiringInfo;
#define CREATE_AREA_UNMAP_ADDRESS_RANGE 0x02
#define CREATE_AREA_DONT_CLEAR 0x04
#define CREATE_AREA_PRIORITY_VIP 0x08
#define CREATE_AREA_DONT_COMMIT_MEMORY 0x10
// memory/page allocation priorities
#define VM_PRIORITY_USER 0

10
src/system/kernel/vm/vm.cpp
View File

@ -794,9 +794,11 @@ map_backing_store(VMAddressSpace* addressSpace, VMCache* cache,
cache = newCache;
}
status = cache->SetMinimalCommitment(size, priority);
if (status != B_OK)
goto err2;
if ((flags & CREATE_AREA_DONT_COMMIT_MEMORY) == 0) {
status = cache->SetMinimalCommitment(size, priority);
if (status != B_OK)
goto err2;
}
// check to see if this address space has entered DELETE state
if (addressSpace->IsBeingDeleted()) {
@ -2229,7 +2231,7 @@ vm_copy_area(team_id team, const char* name, void** _address,
status = map_backing_store(targetAddressSpace, cache, _address,
source->cache_offset, source->Size(), addressSpec, source->wiring,
protection, sharedArea ? REGION_NO_PRIVATE_MAP : REGION_PRIVATE_MAP,
&target, name, 0, true);
&target, name, writableCopy ? 0 : CREATE_AREA_DONT_COMMIT_MEMORY, true);
if (status < B_OK)
return status;