GMMR0.cpp revision ed94f5cfa0c2aec25488cc7cf414603c709fd4f6
/* $Id$ */
/** @file
* GMM - Global Memory Manager.
*/
/*
* Copyright (C) 2007 InnoTek Systemberatung GmbH
*
* This file is part of VirtualBox Open Source Edition (OSE), as
* available from http://www.virtualbox.org. This file is free software;
* General Public License as published by the Free Software Foundation,
* in version 2 as it comes in the "COPYING" file of the VirtualBox OSE
* distribution. VirtualBox OSE is distributed in the hope that it will
* be useful, but WITHOUT ANY WARRANTY of any kind.
*
*/
/** @page pg_gmm GMM - The Global Memory Manager
*
* As the name indicates, this component is responsible for global memory
* management. Currently only guest RAM is allocated from the GMM, but this
* may change to include shadow page tables and other bits later.
*
* Guest RAM is managed as individual pages, but allocated from the host OS
* in chunks for reasons of portability / efficiency. To minimize the memory
* footprint all tracking structure must be as small as possible without
* unnecessary performance penalties.
*
*
* The allocation chunks has fixed sized, the size defined at compile time
* by the GMM_CHUNK_SIZE \#define.
*
* Each chunk is given an unquie ID. Each page also has a unique ID. The
* relation ship between the two IDs is:
* @verbatim
(idChunk << GMM_CHUNK_SHIFT) | iPage
@endverbatim
* Where GMM_CHUNK_SHIFT is log2(GMM_CHUNK_SIZE / PAGE_SIZE) and iPage is
* the index of the page within the chunk. This ID scheme permits for efficient
* chunk and page lookup, but it relies on the chunk size to be set at compile
* time. The chunks are organized in an AVL tree with their IDs being the keys.
*
* The physical address of each page in an allocation chunk is maintained by
* the RTR0MEMOBJ and obtained using RTR0MemObjGetPagePhysAddr. There is no
* need to duplicate this information (it'll cost 8-bytes per page if we did).
*
* So what do we need to track per page? Most importantly we need to know what
* state the page is in:
* - Private - Allocated for (eventually) backing one particular VM page.
* - Shared - Readonly page that is used by one or more VMs and treated
* as COW by PGM.
* - Free - Not used by anyone.
*
* For the page replacement operations (sharing, defragmenting and freeing)
* to be somewhat efficient, private pages needs to be associated with a
* particular page in a particular VM.
*
* Tracking the usage of shared pages is impractical and expensive, so we'll
* settle for a reference counting system instead.
*
* Free pages will be chained on LIFOs
*
* On 64-bit systems we will use a 64-bit bitfield per page, while on 32-bit
* systems a 32-bit bitfield will have to suffice because of address space
* limitations. The GMMPAGE structure shows the details.
*
*
* @section sec_gmm_costs Page Allocation Strategy
*
* The strategy for allocating pages has to take fragmentation and shared
* pages into account, or we may end up with with 2000 chunks with only
* a few pages in each. The fragmentation wrt shared pages is that unlike
* private pages they cannot easily be reallocated. Private pages can be
* reallocated by a defragmentation thread in the same manner that sharing
* is done.
*
* The first approach is to manage the free pages in two sets depending on
* whether they are mainly for the allocation of shared or private pages.
* In the initial implementation there will be almost no possibility for
* mixing shared and private pages in the same chunk (only if we're really
* stressed on memory), but when we implement forking of VMs and have to
* deal with lots of COW pages it'll start getting kind of interesting.
*
* The sets are lists of chunks with approximately the same number of
* free pages. Say the chunk size is 1MB, meaning 256 pages, and a set
* consists of 16 lists. So, the first list will contain the chunks with
* 1-7 free pages, the second covers 8-15, and so on. The chunks will be
* moved between the lists as pages are freed up or allocated.
*
*
* @section sec_gmm_costs Costs
*
* The per page cost in kernel space is 32-bit plus whatever RTR0MEMOBJ
* entails. In addition there is the chunk cost of approximately
* (sizeof(RT0MEMOBJ) + sizof(CHUNK)) / 2^CHUNK_SHIFT bytes per page.
*
* On Windows the per page RTR0MEMOBJ cost is 32-bit on 32-bit windows
* and 64-bit on 64-bit windows (a PFN_NUMBER in the MDL). So, 64-bit per page.
* The cost on Linux is identical, but here it's because of sizeof(struct page *).
*
*
* @section sec_gmm_legacy Legacy Mode for Non-Tier-1 Platforms
*
* In legacy mode the page source is locked user pages and not
* RTR0MemObjAllocPhysNC, this means that a page can only be allocated
* by the VM that locked it. We will make no attempt at implementing
* page sharing on these systems, just do enough to make it all work.
*
*
* @subsection sub_gmm_locking Serializing
*
* One simple fast mutex will be employed in the initial implementation, not
* two as metioned in @ref subsec_pgmPhys_Serializing.
*
* @see subsec_pgmPhys_Serializing
*
*
* @section sec_gmm_overcommit Memory Over-Commitment Management
*
* The GVM will have to do the system wide memory over-commitment
* management. My current ideas are:
* - Per VM oc policy that indicates how much to initially commit
* to it and what to do in a out-of-memory situation.
* - Prevent overtaxing the host.
*
* There are some challenges here, the main ones are configurability and
* security. Should we for instance permit anyone to request 100% memory
* commitment? Who should be allowed to do runtime adjustments of the
* config. And how to prevent these settings from being lost when the last
* VM process exits? The solution is probably to have an optional root
* daemon the will keep VMMR0.r0 in memory and enable the security measures.
*
* This will not be implemented this week. :-)
*
*/
/*******************************************************************************
* Header Files *
*******************************************************************************/
#include "../PGMInternal.h"
/*******************************************************************************
* Structures and Typedefs *
*******************************************************************************/
/**
* The per-page tracking structure employed by the GMM.
*
* On 32-bit hosts we'll some trickery is necessary to compress all
* the information into 32-bits. When the fSharedFree member is set,
* the 30th bit decides whether it's a free page or not.
*
* Because of the different layout on 32-bit and 64-bit hosts, macros
* are used to set and get the data.
*/
typedef union GMMPAGE
{
#if HC_ARCH_BITS == 64
/** Unsigned integer view. */
uint64_t u;
/** The common view. */
struct GMMPAGECOMMON
{
/** The page state. */
} Common;
/** The view of a private page. */
struct GMMPAGEPRIVATE
{
/** The guest page frame number. (Max addressable: 2 ^ 44) */
/** The GVM handle. (64K VMs) */
/** Reserved. */
/** The page state. */
} Private;
/** The view of a shared page. */
struct GMMPAGESHARED
{
/** The reference count. */
/** Reserved. Checksum or something? Two hGVMs for forking? */
/** The page state. */
} Shared;
/** The view of a free page. */
struct GMMPAGEFREE
{
/** The id of the next page in the free list. */
/** Reserved. Checksum or something? */
/** The page state. */
} Free;
#else /* 32-bit */
/** The common view. */
struct GMMPAGECOMMON
{
/** The page state. */
} Common;
/** The view of a private page. */
struct GMMPAGEPRIVATE
{
/** The guest page frame number. (Max addressable: 2 ^ 36) */
/** The GVM handle. (127 VMs) */
/** The top page state bit, MBZ. */
} Private;
/** The view of a shared page. */
struct GMMPAGESHARED
{
/** The reference count. */
/** The page state. */
} Shared;
/** The view of a free page. */
struct GMMPAGEFREE
{
/** The id of the next page in the free list. */
/** Reserved. Checksum or something? */
/** The page state. */
} Free;
#endif
} GMMPAGE;
/** Pointer to a GMMPAGE. */
/** @name The Page States.
* @{ */
/** A private page. */
#define GMM_PAGE_STATE_PRIVATE 0
/** A private page - alternative value used on the 32-bit implemenation.
* This will never be used on 64-bit hosts. */
#define GMM_PAGE_STATE_PRIVATE_32 1
/** A shared page. */
#define GMM_PAGE_STATE_SHARED 2
/** A free page. */
#define GMM_PAGE_STATE_FREE 3
/** @} */
/** @def GMMPAGE_IS_PRIVATE
*
* @returns true if free, false if not.
* @param pPage The GMM page.
*/
#if HC_ARCH_BITS == 64
#else
#endif
/** @def GMMPAGE_IS_FREE
*
* @returns true if free, false if not.
* @param pPage The GMM page.
*/
/** @def GMMPAGE_IS_FREE
*
* @returns true if free, false if not.
* @param pPage The GMM page.
*/
/**
* A GMM allocation chunk ring-3 mapping record.
*
* This should really be associated with a session and not a VM, but
* it's simpler to associated with a VM and cleanup with the VM object
* is destroyed.
*/
typedef struct GMMCHUNKMAP
{
/** The mapping object. */
/** The VM owning the mapping. */
} GMMCHUNKMAP;
/** Pointer to a GMM allocation chunk mapping. */
typedef struct GMMCHUNKMAP *PGMMCHUNKMAP;
/** Pointer to a GMM allocation chunk. */
/**
* A GMM allocation chunk.
*/
typedef struct GMMCHUNK
{
/** The AVL node core.
* The Key is the chunk ID. */
/** The memory object.
* This is either a */
/** Pointer to the next chunk in the free list. */
/** Pointer to the previous chunk in the free list. */
/** Pointer to an array of mappings. */
/** The number of mappings. */
/** The head of the list of free pages. */
/** The number of free pages. */
/** The GVM handle of the VM that first allocated pages from this chunk, this
* is used as a preference when there are several chunks to choose from.
* When in legacy mode this isn't a preference any longer. */
/** The number of private pages. */
/** The number of shared pages. */
/** Reserved for later. */
/** The pages. */
} GMMCHUNK;
/**
* An allocation chunk TLB entry.
*/
typedef struct GMMCHUNKTLBE
{
/** The chunk id. */
/** Pointer to the chunk. */
} GMMCHUNKTLBE;
/** Pointer to an allocation chunk TLB entry. */
typedef GMMCHUNKTLBE *PGMMCHUNKTLBE;
/**
* An allocation chunk TLB.
*/
typedef struct GMMCHUNKTLB
{
/** The TLB entries. */
} GMMCHUNKTLB;
/** Pointer to an allocation chunk TLB. */
typedef GMMCHUNKTLB *PGMMCHUNKTLB;
/**
* A set of free chunks.
*/
typedef struct GMMCHUNKFREESET
{
/** The number of free pages in the set. */
/** */
/** Pointer to set of free chunks. */
typedef GMMCHUNKFREESET *PGMMCHUNKFREESET;
/**
* The GMM instance data.
*/
typedef struct GMM
{
/** Magic / eye catcher. GMM_MAGIC */
/** The fast mutex protecting the GMM.
* More fine grained locking can be implemented later if necessary. */
/** The chunk tree. */
/** The chunk TLB. */
/** The private free set. */
/** The shared free set. */
/** The number of allocated pages. */
/** The legacy mode indicator.
* This is determined at initialization time. */
bool fLegacyMode;
} GMM;
/** Pointer to the GMM instance. */
/** The value of GMM::u32Magic (Katsuhiro Otomo). */
#define GMM_MAGIC 0x19540414
/*******************************************************************************
* Internal Functions *
*******************************************************************************/
/**
* Initializes the GMM component.
*
* This is called when the VMMR0.r0 module is loaded and protected by the
* loader semaphore.
*
* @returns VBox status code.
*/
{
LogFlow(("GMMInit:\n"));
/*
* Allocate the instance data and the lock(s).
*/
if (!pGMM)
return VERR_NO_MEMORY;
if (RT_SUCCESS(rc))
{
/*
* Check and see if RTR0MemObjAllocPhysNC works.
*/
if (RT_SUCCESS(rc))
{
}
else if (rc == VERR_NOT_SUPPORTED)
pGMM->fLegacyMode = true;
else
return VINF_SUCCESS;
}
return rc;
}
/**
* Terminates the GMM component.
*/
{
LogFlow(("GMMTerm:\n"));
/*
* Take care / be paranoid...
*/
return;
{
return;
}
/*
* Undo what init did and free any resources we've acquired.
*/
/* Destroy the fundamentals. */
/* free any chunks still hanging around. */
/* finally the instance data itself. */
LogFlow(("GMMTerm: done\n"));
}
/**
* RTAvlU32Destroy callback.
*
* @returns 0
* @param pNode The node to destroy.
* @param pvGMM The GMM handle.
*/
{
if (RT_FAILURE(rc))
{
}
return 0;
}
/**
* Cleans up when a VM is terminated.
*
* @param pVM The VM structure.
* @param hGVM The global VM handle.
*/
{
return;
/*
* Walk the entire pool looking for pages that belongs to this VM.
* This is slow but necessary. Of course it won't work for shared
* pages, but we'll deal with that later.
*/
/*
* Update over-commitment management and free chunks that are no
* longer needed. If no VMs are around, free everything.
*/
LogFlow(("GMMR0CleanupVM: returns\n"));
}