/** caller handles locking */
static bool PREPLOGBUFFER(BufBuilder& bb) {
if( writes.empty() )
return false;
bb.reset();
unsigned *lenInBlockHeader;
{
// JSectHeader
bb.appendStr("\nHH\n", false);
lenInBlockHeader = (unsigned *) bb.skip(4);
}
string lastFilePath;
{
scoped_lock lk(privateViews._mutex());
for( vector<WriteIntent>::iterator i = writes.begin(); i != writes.end(); i++ ) {
size_t ofs;
MongoMMF *mmf = privateViews._find(i->p, ofs);
if( mmf == 0 ) {
journalingFailure("view pointer cannot be resolved");
}
else {
if( mmf->filePath() != lastFilePath ) {
lastFilePath = mmf->filePath();
JDbContext c;
bb.appendStruct(c);
bb.appendStr(lastFilePath);
}
JEntry e;
e.len = i->len;
e.fileNo = mmf->fileSuffixNo();
bb.appendStruct(e);
bb.appendBuf(i->p, i->len);
}
}
}
{
JSectFooter f;
f.hash = 0;
bb.appendStruct(f);
}
{
unsigned L = (bb.len() + 8191) & 0xffffe000; // fill to alignment
dassert( L >= (unsigned) bb.len() );
*lenInBlockHeader = L;
unsigned padding = L - bb.len();
bb.skip(padding);
dassert( bb.len() % 8192 == 0 );
}
writes.clear();
alreadyNoted.clear();
return true;
}
void* writingPtr(void *x, size_t len) {
//log() << "TEMP writing " << x << ' ' << len << endl;
void *p = x;
DEV p = MongoMMF::switchToPrivateView(x);
WriteIntent w(p, len);
if( !alreadyNoted.checkAndSet(w) ) {
// remember intent. we will journal it in a bit
writes.push_back(w);
wassert( writes.size() < 2000000 );
assert( writes.size() < 20000000 );
}
return p;
}
namespace dur {
//MongoMMF* pointerToMMF(void *p, size_t& ofs);
struct WriteIntent {
WriteIntent() : p(0) { }
WriteIntent(void *a, unsigned b) : p(a), len(b) { }
void *p; // where we will write
unsigned len; // up to this len
};
/* try to remember things we have already marked for journalling. false negatives are ok if infrequent -
we will just log them twice.
*/
template<int Prime>
class Already {
enum { N = Prime }; // this should be small the idea is that it fits in the cpu cache easily
WriteIntent nodes[N];
public:
Already() { clear(); }
void clear() { memset(this, 0, sizeof(*this)); }
/* see if we have Already recorded/indicated our write intent for this region of memory.
@return true if already indicated.
*/
bool checkAndSet(const WriteIntent& w) {
unsigned x = mongoutils::hashPointer(w.p);
WriteIntent& nd = nodes[x % N];
if( nd.p != w.p || nd.len < w.len ) {
nd = w;
return false;
}
return true;
}
};
static Already<127> alreadyNoted;
/* our record of pending/uncommitted write intents */
static vector<WriteIntent> writes;
void* writingPtr(void *x, size_t len) {
//log() << "TEMP writing " << x << ' ' << len << endl;
void *p = x;
DEV p = MongoMMF::switchToPrivateView(x);
WriteIntent w(p, len);
if( !alreadyNoted.checkAndSet(w) ) {
// remember intent. we will journal it in a bit
writes.push_back(w);
wassert( writes.size() < 2000000 );
assert( writes.size() < 20000000 );
}
return p;
}
/** caller handles locking */
static bool PREPLOGBUFFER(BufBuilder& bb) {
if( writes.empty() )
return false;
bb.reset();
unsigned *lenInBlockHeader;
{
// JSectHeader
bb.appendStr("\nHH\n", false);
lenInBlockHeader = (unsigned *) bb.skip(4);
}
string lastFilePath;
{
scoped_lock lk(privateViews._mutex());
for( vector<WriteIntent>::iterator i = writes.begin(); i != writes.end(); i++ ) {
size_t ofs;
MongoMMF *mmf = privateViews._find(i->p, ofs);
if( mmf == 0 ) {
journalingFailure("view pointer cannot be resolved");
}
else {
if( mmf->filePath() != lastFilePath ) {
lastFilePath = mmf->filePath();
JDbContext c;
bb.appendStruct(c);
bb.appendStr(lastFilePath);
}
JEntry e;
e.len = i->len;
e.fileNo = mmf->fileSuffixNo();
bb.appendStruct(e);
bb.appendBuf(i->p, i->len);
}
}
}
{
JSectFooter f;
f.hash = 0;
bb.appendStruct(f);
}
{
unsigned L = (bb.len() + 8191) & 0xffffe000; // fill to alignment
dassert( L >= (unsigned) bb.len() );
*lenInBlockHeader = L;
unsigned padding = L - bb.len();
bb.skip(padding);
dassert( bb.len() % 8192 == 0 );
}
writes.clear();
alreadyNoted.clear();
return true;
}
static void WRITETOJOURNAL(const BufBuilder& bb) {
journal(bb);
}
static void _go(BufBuilder& bb) {
PREPLOGBUFFER(bb);
// todo: add double buffering so we can be (not even read locked) during WRITETOJOURNAL
WRITETOJOURNAL(bb);
}
static void go(BufBuilder& bb) {
{
readlocktry lk("", 1000);
if( lk.got() ) {
_go(bb);
return;
}
}
// starvation on read locks could occur. so if read lock acquisition is slow, try to get a
// write lock instead. otherwise writes could use too much RAM.
writelock lk;
_go(bb);
}
static void durThread() {
Client::initThread("dur");
const int HowOftenToGroupCommitMs = 100;
BufBuilder bb(1024 * 1024 * 16); // reuse to avoid any heap fragmentation
while( 1 ) {
try {
int millis = HowOftenToGroupCommitMs;
{
Timer t;
journalRotate(); // note we do this part outside of mongomutex
millis -= t.millis();
if( millis < 5 || millis > HowOftenToGroupCommitMs )
millis = 5;
}
sleepmillis(millis);
go(bb);
}
catch(std::exception& e) {
log() << "exception in durThread " << e.what() << endl;
}
}
}
void startup() {
journalMakeDir();
boost::thread t(durThread);
}
} // namespace dur
void clear() {
_alreadyNoted.clear();
_writes.clear();
}