HeapPT_Starter.h

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/*
* Copyright 2015 Autodesk, Inc. All rights reserved.
* Use of this software is subject to the terms of the Autodesk license agreement and any attachments or Appendices thereto provided at the time of installation or download,
* or which otherwise accompanies this software in either electronic or hard copy form, or which is signed by you and accepted by Autodesk.
*/

/**************************************************************************

Filename    :   HeapPT_Starter.h
Content     :   Starter allocator
Created     :   2009
Authors     :   Maxim Shemanarev

Notes       :   Internal allocator used for the initial bootstrapping.
                It allocates/frees the page mapping arrays.

**************************************************************************/

#ifndef INC_KY_Kernel_Heap_Starter_H
#define INC_KY_Kernel_Heap_Starter_H

#include "gwnavruntime/kernel/HeapPT/HeapPT_Granulator.h"

namespace Kaim { namespace HeapPT {

// ***** Starter
//
// Internal allocator used for the initial bootstrapping. 
// It allocates/frees the page mapping arrays, but can also be used
// as a general purpose allocator that requires the allocation size 
// when freeing memory.
//
// The starter is just optimized for pages of the same size. On 64-bit 
// platforms the pages can have different sizes, but definitely there 
// will not be a great variety of sizes. Most of the requests will be 
// of the same size, only few of them will have a bigger size.
//
// On 32-bit platforms, the detailed situation looks like this:
// Assume HeaderPageSize=4k, Granularity=16K, and allocation requests 
// for exactly 1K PageTables.
// One PageTable (1K) can serve 1MB, one header can serve 16 PageTables,
// that is, 16 MB. One header page can keep information about 204 headers,
// that is, all in all it can serve space of 3264 MB. Only after exceeding
// it (if anything is left available) the starter has to allocate the second 
// header page to serve the rest of physically available 4 GB of address 
// space (not to mention on 32-bit WinXP/Vista only 3GB is available). 
//
// On 64-bit platforms, the situation is heavier, but still, remains 
// quite acceptable. You probably have to increase the "HeaderPageSize" 
// and "Granularity". In 64-bit case HeaderPageSize=8K and Granularity=32K
// will serve the requests perfectly.
//
// The only restriction is: HeaderPageSize and Granularity cannot be
// less than Heap_PageSize.
//------------------------------------------------------------------------
class Starter
{
public:
    Starter(SysAllocPaged* sysAlloc, 
            UPInt granularity    = 4*Heap_PageSize, 
            UPInt headerPageSize = 1*Heap_PageSize);

    SysAllocPaged* GetSysAlloc() { return Allocator.GetSysAlloc(); }

    void*   Alloc(UPInt size, UPInt alignSize);
    void    Free(void* ptr, UPInt size, UPInt alignSize); // Size is required!

    void    VisitMem(MemVisitor* visitor) const;
    void    VisitSegments(class SegVisitor* visitor) const;

    UPInt   GetFootprint() const { return Allocator.GetFootprint(); }
    UPInt   GetUsedSpace() const { return Allocator.GetUsedSpace(); }

private:
    Granulator Allocator;
};

}} // Kaim::Heap

#endif