Source code of Windows XP (NT5)
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/*++
Copyright (c) 1995 Microsoft Corporation
Module Name:
lookasid.c
Abstract:
This module implements lookaside list function.
Author:
David N. Cutler (davec) 19-Feb-1995
Revision History:
--*/
#include "exp.h"
#pragma alloc_text(PAGE, ExInitializePagedLookasideList)
//
// Define Minimum lookaside list depth.
//
#define MINIMUM_LOOKASIDE_DEPTH 4
//
// Define minimum allocation threshold.
//
#define MINIMUM_ALLOCATION_THRESHOLD 25
//
// Define forward referenced function prototypes.
//
PVOID
ExpDummyAllocate (
IN POOL_TYPE PoolType,
IN SIZE_T NumberOfBytes,
IN ULONG Tag
);
VOID
ExpScanGeneralLookasideList (
IN PLIST_ENTRY ListHead,
IN PKSPIN_LOCK SpinLock
);
VOID
ExpScanSystemLookasideList (
VOID
);
//
// Define the global nonpaged and paged lookaside list data.
//
LIST_ENTRY ExNPagedLookasideListHead;
KSPIN_LOCK ExNPagedLookasideLock;
LIST_ENTRY ExPagedLookasideListHead;
KSPIN_LOCK ExPagedLookasideLock;
LIST_ENTRY ExPoolLookasideListHead;
LIST_ENTRY ExSystemLookasideListHead;
//
// Define lookaside list dynamic adjustment data.
//
ULONG ExpPoolScanCount = 0;
ULONG ExpScanCount = 0;
VOID
ExAdjustLookasideDepth (
VOID
)
/*++
Routine Description:
This function is called periodically to adjust the maximum depth of
all lookaside lists.
Arguments:
None.
Return Value:
None.
--*/
{
//
// Switch on the current scan count.
//
switch (ExpScanCount) {
//
// Scan the general nonpaged lookaside lists.
//
case 0:
ExpScanGeneralLookasideList(&ExNPagedLookasideListHead,
&ExNPagedLookasideLock);
break;
//
// Scan the general paged lookaside lists.
//
case 1:
ExpScanGeneralLookasideList(&ExPagedLookasideListHead,
&ExPagedLookasideLock);
break;
//
// Scan the pool paged and nonpaged lookaside lists.
//
// N.B. Only one set of pool paged and nonpaged lookaside lists
// are scanned each scan period.
//
case 2:
ExpScanSystemLookasideList();
break;
}
//
// Increment the scan count. If a complete cycles has been completed,
// then zero the scan count and check if any changes occurred during
// the complete scan.
//
ExpScanCount += 1;
if (ExpScanCount == 3) {
ExpScanCount = 0;
}
return;
}
FORCEINLINE
VOID
ExpComputeLookasideDepth (
IN PGENERAL_LOOKASIDE Lookaside,
IN ULONG Misses,
IN ULONG ScanPeriod
)
/*++
Routine Description:
This function computes the target depth of a lookaside list given the
total allocations and misses during the last scan period and the current
depth.
Arguments:
Lookaside - Supplies a pointer to a lookaside list descriptor.
Misses - Supllies the total number of allocate misses.
ScanPeriod - Supplies the scan period in seconds.
Return Value:
None.
--*/
{
ULONG Allocates;
ULONG Delta;
USHORT MaximumDepth;
ULONG Ratio;
LONG Target;
//
// Compute the total number of allocations and misses per second for
// this scan period.
//
Allocates = Lookaside->TotalAllocates - Lookaside->LastTotalAllocates;
Lookaside->LastTotalAllocates = Lookaside->TotalAllocates;
MaximumDepth = Lookaside->MaximumDepth;
//
// If the allocate rate is less than the mimimum threshold, then lower
// the maximum depth of the lookaside list. Otherwise, if the miss rate
// is less than .5%, then lower the maximum depth. Otherwise, raise the
// maximum depth based on the miss rate.
//
Target = Lookaside->Depth;
if (Allocates < (ScanPeriod * MINIMUM_ALLOCATION_THRESHOLD)) {
if ((Target -= 10) < MINIMUM_LOOKASIDE_DEPTH) {
Target = MINIMUM_LOOKASIDE_DEPTH;
}
} else {
//
// N.B. The number of allocates is guaranteed to be greater than
// zero because of the above test.
//
// N.B. It is possible that the number of misses are greater than the
// number of allocates, but this won't cause the an incorrect
// computation of the depth adjustment.
//
Ratio = (Misses * 1000) / Allocates;
if (Ratio < 5) {
if ((Target -= 1) < MINIMUM_LOOKASIDE_DEPTH) {
Target = MINIMUM_LOOKASIDE_DEPTH;
}
} else {
if ((Delta = ((Ratio * (MaximumDepth - Target)) / (1000 * 2)) + 5) > 30) {
Delta = 30;
}
if ((Target += Delta) > MaximumDepth) {
Target = MaximumDepth;
}
}
}
Lookaside->Depth = (USHORT)Target;
return;
}
VOID
ExpScanGeneralLookasideList (
IN PLIST_ENTRY ListHead,
IN PKSPIN_LOCK SpinLock
)
/*++
Routine Description:
This function scans the specified list of general lookaside descriptors
and adjusts the maximum depth as necessary.
Arguments:
ListHead - Supplies the address of the listhead for a list of lookaside
descriptors.
SpinLock - Supplies the address of the spinlock to be used to synchronize
access to the list of lookaside descriptors.
Return Value:
None.
--*/
{
PLIST_ENTRY Entry;
PPAGED_LOOKASIDE_LIST Lookaside;
ULONG Misses;
KIRQL OldIrql;
#ifdef NT_UP
UNREFERENCED_PARAMETER (SpinLock);
#endif
//
// Raise IRQL and acquire the specified spinlock.
//
ExAcquireSpinLock(SpinLock, &OldIrql);
//
// Scan the specified list of lookaside descriptors and adjust the
// maximum depth as necessary.
//
// N.B. All lookaside list descriptor are treated as if they were
// paged descriptor even though they may be nonpaged descriptors.
// This is possible since both structures are identical except
// for the locking fields which are the last structure fields.
//
Entry = ListHead->Flink;
while (Entry != ListHead) {
Lookaside = CONTAINING_RECORD(Entry,
PAGED_LOOKASIDE_LIST,
L.ListEntry);
//
// Compute target depth of lookaside list.
//
Misses = Lookaside->L.AllocateMisses - Lookaside->L.LastAllocateMisses;
Lookaside->L.LastAllocateMisses = Lookaside->L.AllocateMisses;
ExpComputeLookasideDepth(&Lookaside->L, Misses, 3);
Entry = Entry->Flink;
}
//
// Release spinlock, lower IRQL, and return function value.
//
ExReleaseSpinLock(SpinLock, OldIrql);
return;
}
VOID
ExpScanSystemLookasideList (
VOID
)
/*++
Routine Description:
This function scans the current set of paged and nonpaged pool lookaside
descriptors and adjusts the maximum depth as necessary.
Arguments:
None.
Return Value:
A value of TRUE is returned if the maximum depth of any lookaside list
is changed. Otherwise, a value of FALSE is returned.
--*/
{
ULONG Hits;
ULONG Index;
PGENERAL_LOOKASIDE Lookaside;
ULONG Misses;
PKPRCB Prcb;
ULONG ScanPeriod;
//
// Scan the current set of lookaside descriptors and adjust the maximum
// depth as necessary. Either a set of per processor small pool lookaside
// lists or the global small pool lookaside lists are scanned during a
// scan period.
//
// N.B. All lookaside list descriptor are treated as if they were
// paged descriptor even though they may be nonpaged descriptors.
// This is possible since both structures are identical except
// for the locking fields which are the last structure fields.
//
ScanPeriod = (1 + 1 + 1) * KeNumberProcessors;
if (ExpPoolScanCount == (ULONG)KeNumberProcessors) {
//
// Adjust the maximum depth for the global set of system lookaside
// descriptors.
//
Prcb = KeGetCurrentPrcb();
for (Index = 0; Index < LookasideMaximumList; Index += 1) {
Lookaside = Prcb->PPLookasideList[Index].L;
if (Lookaside != NULL) {
Misses = Lookaside->AllocateMisses - Lookaside->LastAllocateMisses;
Lookaside->LastAllocateMisses = Lookaside->AllocateMisses;
ExpComputeLookasideDepth(Lookaside, Misses, ScanPeriod);
}
}
//
// Adjust the maximum depth for the global set of small pool lookaside
// descriptors.
//
for (Index = 0; Index < POOL_SMALL_LISTS; Index += 1) {
//
// Compute target depth of nonpaged lookaside list.
//
Lookaside = &ExpSmallNPagedPoolLookasideLists[Index];
Hits = Lookaside->AllocateHits - Lookaside->LastAllocateHits;
Lookaside->LastAllocateHits = Lookaside->AllocateHits;
Misses =
Lookaside->TotalAllocates - Lookaside->LastTotalAllocates - Hits;
ExpComputeLookasideDepth(Lookaside, Misses, ScanPeriod);
//
// Compute target depth of paged lookaside list.
//
Lookaside = &ExpSmallPagedPoolLookasideLists[Index];
Hits = Lookaside->AllocateHits - Lookaside->LastAllocateHits;
Lookaside->LastAllocateHits = Lookaside->AllocateHits;
Misses =
Lookaside->TotalAllocates - Lookaside->LastTotalAllocates - Hits;
ExpComputeLookasideDepth(Lookaside, Misses, ScanPeriod);
}
} else {
//
// Adjust the maximum depth for the global set of per processor
// system lookaside descriptors.
//
Prcb = KiProcessorBlock[ExpPoolScanCount];
for (Index = 0; Index < LookasideMaximumList; Index += 1) {
Lookaside = Prcb->PPLookasideList[Index].P;
if (Lookaside != NULL) {
Misses = Lookaside->AllocateMisses - Lookaside->LastAllocateMisses;
Lookaside->LastAllocateMisses = Lookaside->AllocateMisses;
ExpComputeLookasideDepth(Lookaside, Misses, ScanPeriod);
}
}
//
// Adjust the maximum depth for a set of per processor small pool
// lookaside descriptors.
//
for (Index = 0; Index < POOL_SMALL_LISTS; Index += 1) {
//
// Compute target depth of nonpaged lookaside list.
//
Lookaside = Prcb->PPNPagedLookasideList[Index].P;
Hits = Lookaside->AllocateHits - Lookaside->LastAllocateHits;
Lookaside->LastAllocateHits = Lookaside->AllocateHits;
Misses =
Lookaside->TotalAllocates - Lookaside->LastTotalAllocates - Hits;
ExpComputeLookasideDepth(Lookaside, Misses, ScanPeriod);
//
// Compute target depth of paged lookaside list.
//
Lookaside = Prcb->PPPagedLookasideList[Index].P;
Hits = Lookaside->AllocateHits - Lookaside->LastAllocateHits;
Lookaside->LastAllocateHits = Lookaside->AllocateHits;
Misses =
Lookaside->TotalAllocates - Lookaside->LastTotalAllocates - Hits;
ExpComputeLookasideDepth(Lookaside, Misses, ScanPeriod);
}
}
ExpPoolScanCount += 1;
if (ExpPoolScanCount > (ULONG)KeNumberProcessors) {
ExpPoolScanCount = 0;
}
return;
}
VOID
ExInitializeNPagedLookasideList (
IN PNPAGED_LOOKASIDE_LIST Lookaside,
IN PALLOCATE_FUNCTION Allocate,
IN PFREE_FUNCTION Free,
IN ULONG Flags,
IN SIZE_T Size,
IN ULONG Tag,
IN USHORT Depth
)
/*++
Routine Description:
This function initializes a nonpaged lookaside list structure and inserts
the structure in the system nonpaged lookaside list.
Arguments:
Lookaside - Supplies a pointer to a nonpaged lookaside list structure.
Allocate - Supplies an optional pointer to an allocate function.
Free - Supplies an optional pointer to a free function.
Flags - Supplies the pool allocation flags which are merged with the
pool allocation type (NonPagedPool) to control pool allocation.
Size - Supplies the size for the lookaside list entries.
Tag - Supplies the pool tag for the lookaside list entries.
Depth - Supplies the maximum depth of the lookaside list.
Return Value:
None.
--*/
{
#ifdef _IA64_
PVOID Entry;
#endif
UNREFERENCED_PARAMETER (Depth);
//
// Initialize the lookaside list structure.
//
InitializeSListHead(&Lookaside->L.ListHead);
Lookaside->L.Depth = MINIMUM_LOOKASIDE_DEPTH;
Lookaside->L.MaximumDepth = 256; //Depth;
Lookaside->L.TotalAllocates = 0;
Lookaside->L.AllocateMisses = 0;
Lookaside->L.TotalFrees = 0;
Lookaside->L.FreeMisses = 0;
Lookaside->L.Type = NonPagedPool | Flags;
Lookaside->L.Tag = Tag;
Lookaside->L.Size = (ULONG)Size;
if (Allocate == NULL) {
Lookaside->L.Allocate = ExAllocatePoolWithTag;
} else {
Lookaside->L.Allocate = Allocate;
}
if (Free == NULL) {
Lookaside->L.Free = ExFreePool;
} else {
Lookaside->L.Free = Free;
}
Lookaside->L.LastTotalAllocates = 0;
Lookaside->L.LastAllocateMisses = 0;
//
// For IA-64 we have to correctly initialize the region field in the S-list.
// This might be in a different region than the head of the S-list. We get
// correct one by doing a allocation to getting the region and then saving it.
//
#ifdef _IA64_
Entry = (Lookaside->L.Allocate)(Lookaside->L.Type,
Lookaside->L.Size,
Lookaside->L.Tag);
if (Entry != NULL) {
Lookaside->L.ListHead.Region = (ULONG_PTR)Entry & VRN_MASK;
//
// Free the memory.
//
(Lookaside->L.Free)(Entry);
}
#endif
//
// Insert the lookaside list structure is the system nonpaged lookaside
// list.
//
ExInterlockedInsertTailList(&ExNPagedLookasideListHead,
&Lookaside->L.ListEntry,
&ExNPagedLookasideLock);
return;
}
VOID
ExDeleteNPagedLookasideList (
IN PNPAGED_LOOKASIDE_LIST Lookaside
)
/*++
Routine Description:
This function removes a paged lookaside structure from the system paged
lookaside list and frees any entries specified by the lookaside structure.
Arguments:
Lookaside - Supplies a pointer to a nonpaged lookaside list structure.
Return Value:
None.
--*/
{
PVOID Entry;
KIRQL OldIrql;
//
// Acquire the nonpaged system lookaside list lock and remove the
// specified lookaside list structure from the list.
//
ExAcquireSpinLock(&ExNPagedLookasideLock, &OldIrql);
RemoveEntryList(&Lookaside->L.ListEntry);
ExReleaseSpinLock(&ExNPagedLookasideLock, OldIrql);
//
// Remove all pool entries from the specified lookaside structure
// and free them.
//
Lookaside->L.Allocate = ExpDummyAllocate;
while ((Entry = ExAllocateFromNPagedLookasideList(Lookaside)) != NULL) {
(Lookaside->L.Free)(Entry);
}
return;
}
VOID
ExInitializePagedLookasideList (
IN PPAGED_LOOKASIDE_LIST Lookaside,
IN PALLOCATE_FUNCTION Allocate,
IN PFREE_FUNCTION Free,
IN ULONG Flags,
IN SIZE_T Size,
IN ULONG Tag,
IN USHORT Depth
)
/*++
Routine Description:
This function initializes a paged lookaside list structure and inserts
the structure in the system paged lookaside list.
Arguments:
Lookaside - Supplies a pointer to a paged lookaside list structure.
Allocate - Supplies an optional pointer to an allocate function.
Free - Supplies an optional pointer to a free function.
Flags - Supplies the pool allocation flags which are merged with the
pool allocation type (NonPagedPool) to control pool allocation.
Size - Supplies the size for the lookaside list entries.
Tag - Supplies the pool tag for the lookaside list entries.
Depth - Supplies the maximum depth of the lookaside list.
Return Value:
None.
--*/
{
#ifdef _IA64_
PVOID Entry;
#endif
UNREFERENCED_PARAMETER (Depth);
PAGED_CODE()
//
// Initialize the lookaside list structure.
//
InitializeSListHead(&Lookaside->L.ListHead);
Lookaside->L.Depth = MINIMUM_LOOKASIDE_DEPTH;
Lookaside->L.MaximumDepth = 256; //Depth;
Lookaside->L.TotalAllocates = 0;
Lookaside->L.AllocateMisses = 0;
Lookaside->L.TotalFrees = 0;
Lookaside->L.FreeMisses = 0;
Lookaside->L.Type = PagedPool | Flags;
Lookaside->L.Tag = Tag;
Lookaside->L.Size = (ULONG)Size;
if (Allocate == NULL) {
Lookaside->L.Allocate = ExAllocatePoolWithTag;
} else {
Lookaside->L.Allocate = Allocate;
}
if (Free == NULL) {
Lookaside->L.Free = ExFreePool;
} else {
Lookaside->L.Free = Free;
}
Lookaside->L.LastTotalAllocates = 0;
Lookaside->L.LastAllocateMisses = 0;
//
// For IA-64 we have to correctly initialize the region field in the S-list.
// This might be in a different region than the head of the S-list. We get
// correct one by doing a allocation to getting the region and then saving it.
//
#ifdef _IA64_
Entry = (Lookaside->L.Allocate)(Lookaside->L.Type,
Lookaside->L.Size,
Lookaside->L.Tag);
if (Entry != NULL) {
Lookaside->L.ListHead.Region = (ULONG_PTR)Entry & VRN_MASK;
//
// Free the memory.
//
(Lookaside->L.Free)(Entry);
}
#endif
//
// Insert the lookaside list structure in the system paged lookaside
// list.
//
ExInterlockedInsertTailList(&ExPagedLookasideListHead,
&Lookaside->L.ListEntry,
&ExPagedLookasideLock);
return;
}
VOID
ExDeletePagedLookasideList (
IN PPAGED_LOOKASIDE_LIST Lookaside
)
/*++
Routine Description:
This function removes a paged lookaside structure from the system paged
lookaside list and frees any entries specified by the lookaside structure.
Arguments:
Lookaside - Supplies a pointer to a paged lookaside list structure.
Return Value:
None.
--*/
{
PVOID Entry;
KIRQL OldIrql;
//
// Acquire the paged system lookaside list lock and remove the
// specified lookaside list structure from the list.
//
ExAcquireSpinLock(&ExPagedLookasideLock, &OldIrql);
RemoveEntryList(&Lookaside->L.ListEntry);
ExReleaseSpinLock(&ExPagedLookasideLock, OldIrql);
//
// Remove all pool entries from the specified lookaside structure
// and free them.
//
Lookaside->L.Allocate = ExpDummyAllocate;
while ((Entry = ExAllocateFromPagedLookasideList(Lookaside)) != NULL) {
(Lookaside->L.Free)(Entry);
}
return;
}
PVOID
ExpDummyAllocate (
IN POOL_TYPE PoolType,
IN SIZE_T NumberOfBytes,
IN ULONG Tag
)
/*++
Routine Description:
This function is a dummy allocation routine which is used to empty
a lookaside list.
Arguments:
PoolType - Supplies the type of pool to allocate.
NumberOfBytes - supplies the number of bytes to allocate.
Tag - supplies the pool tag.
Return Value:
NULL is returned as the function value.
--*/
{
UNREFERENCED_PARAMETER (PoolType);
UNREFERENCED_PARAMETER (NumberOfBytes);
UNREFERENCED_PARAMETER (Tag);
return NULL;
}