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Kernel: Make purgeable memory a VMObject level concept (again)

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This patch changes the semantics of purgeable memory.

- AnonymousVMObject now has a "purgeable" flag. It can only be set when
  constructing the object. (Previously, all anonymous memory was
  effectively purgeable.)

- AnonymousVMObject now has a "volatile" flag. It covers the entire
  range of physical pages. (Previously, we tracked ranges of volatile
  pages, effectively making it a page-level concept.)

- Non-volatile objects maintain a physical page reservation via the
  committed pages mechanism, to ensure full coverage for page faults.

- When an object is made volatile, it relinquishes any unused committed
  pages immediately. If later made non-volatile again, we then attempt
  to make a new committed pages reservation. If this fails, we return
  ENOMEM to userspace.

mmap() now creates purgeable objects if passed the MAP_PURGEABLE option
together with MAP_ANONYMOUS. anon_create() memory is always purgeable.
This commit is contained in:
Andreas Kling 2021-07-25 01:46:44 +02:00
parent 6bb53d6a80
commit 2d1a651e0a
17 changed files with 189 additions and 1004 deletions
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29
Kernel/Syscalls/mmap.cpp
View file

@ -12,6 +12,7 @@
#include <Kernel/PerformanceEventBuffer.h>
#include <Kernel/PerformanceManager.h>
#include <Kernel/Process.h>
#include <Kernel/VM/AnonymousVMObject.h>
#include <Kernel/VM/MemoryManager.h>
#include <Kernel/VM/PageDirectory.h>
#include <Kernel/VM/PrivateInodeVMObject.h>
@ -217,7 +218,14 @@ KResultOr<FlatPtr> Process::sys$mmap(Userspace<const Syscall::SC_mmap_params*> u
if (map_anonymous) {
auto strategy = map_noreserve ? AllocationStrategy::None : AllocationStrategy::Reserve;
auto region_or_error = space().allocate_region(range.value(), {}, prot, strategy);
RefPtr<AnonymousVMObject> vmobject;
if (flags & MAP_PURGEABLE)
vmobject = AnonymousVMObject::try_create_purgeable_with_size(page_round_up(size), strategy);
else
vmobject = AnonymousVMObject::try_create_with_size(page_round_up(size), strategy);
if (!vmobject)
return ENOMEM;
auto region_or_error = space().allocate_region_with_vmobject(range.value(), vmobject.release_nonnull(), 0, {}, prot, map_shared);
if (region_or_error.is_error())
return region_or_error.error().error();
region = region_or_error.value();
@ -465,23 +473,17 @@ KResultOr<FlatPtr> Process::sys$madvise(Userspace<void*> address, size_t size, i
if (set_volatile || set_nonvolatile) {
if (!region->vmobject().is_anonymous())
return EPERM;
auto& vmobject = static_cast<AnonymousVMObject&>(region->vmobject());
bool was_purged = false;
switch (region->set_volatile(VirtualAddress(address), size, set_volatile, was_purged)) {
case Region::SetVolatileError::Success:
break;
case Region::SetVolatileError::NotPurgeable:
return EPERM;
case Region::SetVolatileError::OutOfMemory:
return ENOMEM;
}
if (set_nonvolatile)
return was_purged ? 1 : 0;
return 0;
auto result = vmobject.set_volatile(set_volatile, was_purged);
if (result.is_error())
return result.error();
return was_purged ? 1 : 0;
}
if (advice & MADV_GET_VOLATILE) {
if (!region->vmobject().is_anonymous())
return EPERM;
return region->is_volatile(VirtualAddress(address), size) ? 0 : 1;
return static_cast<AnonymousVMObject&>(region->vmobject()).is_volatile() ? 0 : 1;
}
return EINVAL;
}
@ -668,5 +670,4 @@ KResultOr<FlatPtr> Process::sys$msyscall(Userspace<void*> address)
region->set_syscall_region(true);
return 0;
}
}