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// record.cpp
#include "../pch.h"
#include "pdfile.h"
#include "../util/processinfo.h"
#include "../util/message.h"
#define _BACKWARD_BACKWARD_WARNING_H 1
#include <hash_map>
using namespace __gnu_cxx;
namespace mongo {
namespace ps {
enum State {
IN , OUT , UNK
};
enum Constants {
SliceSize = 65536 ,
MaxChain = 20 , // intentionally very low
NumSlices = 10 ,
RotateTimeSecs = 90
};
int hash( size_t region ) {
return
abs( ( ( 7 + (int)(region & 0xFFFF) ) *
( 11 + (int)( ( region >> 16 ) & 0xFFFF ) ) *
( 13 + (int)( ( region >> 32 ) & 0xFFFF ) ) *
( 17 + (int)( ( region >> 48 ) & 0xFFFF ) ) ) % SliceSize );
}
/**
* simple hash map for region -> status
* this constitures a single region of time
* it does chaining, but very short chains
*/
class Slice {
struct Entry {
size_t region;
unsigned long long value;
};
public:
Slice() {
reset();
}
void reset() {
memset( _data , 0 , SliceSize * sizeof(Entry) );
}
State get( size_t region , short offset ) {
Entry * e = _get( region , false );
if ( ! e )
return UNK;
return ( e->value & ( 1 << offset ) ) ? IN : OUT;
}
/**
* @return true if added, false if full
*/
bool in( size_t region , short offset ) {
Entry * e = _get( region , true );
if ( ! e )
return false;
e->value |= ( 1 << offset );
return true;
}
private:
Entry* _get( size_t region , bool add ) {
int start = hash( region );
for ( int i=0; i<MaxChain; i++ ) {
int bucket = ( start + i ) % SliceSize;
if ( _data[bucket].region == 0 ) {
if ( ! add )
return 0;
_data[bucket].region = region;
return &_data[bucket];
}
if ( _data[bucket].region == region ) {
return &_data[bucket];
}
}
return 0;
}
Entry _data[SliceSize];
};
/**
* this contains many slices of times
* the idea you put mem status in the current time slice
* and then after a certain period of time, it rolls off so we check again
*/
class Rolling {
public:
Rolling() {
_curSlice = 0;
_lastRotate = Listener::getElapsedTimeMillis();
}
/**
* after this call, we assume the page is in ram
* @return whether we know the page is in ram
*/
bool access( size_t region , short offset ) {
RARELY {
long long now = Listener::getElapsedTimeMillis();
OCCASIONALLY if ( now == 0 ) {
warning() << "Listener::getElapsedTimeMillis returing 0" << endl;
}
if ( now - _lastRotate > ( 1000 * RotateTimeSecs ) ) {
_rotate();
}
}
for ( int i=0; i<NumSlices; i++ ) {
int pos = (_curSlice+i)%NumSlices;
State s = _slices[pos].get( region , offset );
if ( s == IN )
return true;
if ( s == OUT ) {
_slices[pos].in( region , offset );
return false;
}
}
// we weren't in any slice
// so add to cur
if ( ! _slices[_curSlice].in( region , offset ) ) {
_rotate();
_slices[_curSlice].in( region , offset );
}
return false;
}
private:
void _rotate() {
_curSlice = ( _curSlice + 1 ) % NumSlices;
_slices[_curSlice].reset();
_lastRotate = Listener::getElapsedTimeMillis();
}
int _curSlice;
long long _lastRotate;
Slice _slices[NumSlices];
};
}
int __record_touch_dummy = 1; // this is used to make sure the compiler doesn't get too smart on us
void Record::touch( bool entireRecrd ) {
if ( lengthWithHeaders > HeaderSize ) { // this also makes sure lengthWithHeaders is in memory
char * addr = data;
char * end = data + netLength();
for ( ; addr <= end ; addr += 2048 )
__record_touch_dummy += addr[0];
}
}
bool Record::likelyInPhysicalMemory() {
static bool blockSupported = ProcessInfo::blockCheckSupported();
static ps::Rolling rolling;
const size_t page = (size_t)data >> 12;
const size_t region = page >> 6;
const size_t offset = page & 0x3f;
if ( rolling.access( region , offset ) )
return true;
if ( ! blockSupported )
return false;
return ProcessInfo::blockInMemory( data );
}
}
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