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/* @file dur_commitjob.h used by dur.cpp */
/**
* Copyright (C) 2009 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/db/cmdline.h"
#include "mongo/db/d_concurrency.h"
#include "mongo/db/dur.h"
#include "mongo/db/durop.h"
#include "mongo/db/taskqueue.h"
#include "mongo/util/alignedbuilder.h"
#include "mongo/util/concurrency/synchronization.h"
#include "mongo/util/mongoutils/hash.h"
namespace mongo {
namespace dur {
void assertLockedForCommitting();
/** Declaration of an intent to write to a region of a memory mapped view
* We store the end rather than the start pointer to make operator< faster
* since that is heavily used in set lookup.
*/
struct WriteIntent { /* copyable */
WriteIntent() : p(0) { }
WriteIntent(void *a, unsigned b) : p((char*)a+b), len(b) { }
void* start() const { return (char*)p - len; }
void* end() const { return p; }
unsigned length() const { return len; }
bool operator < (const WriteIntent& rhs) const { return end() < rhs.end(); }
bool overlaps(const WriteIntent& rhs) const { return (start() <= rhs.end() && end() >= rhs.start()); }
bool contains(const WriteIntent& rhs) const { return (start() <= rhs.start() && end() >= rhs.end()); }
// merge into me:
void absorb(const WriteIntent& other);
friend ostream& operator << (ostream& out, const WriteIntent& wi) {
return (out << "p: " << wi.p << " end: " << wi.end() << " len: " << wi.len);
}
private:
void *p; // intent to write up to p
unsigned len; // up to this len
};
/** try to remember things we have already marked for journaling. false negatives are ok if infrequent -
we will just log them twice.
*/
template<int Prime>
class Already : boost::noncopyable {
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.
automatically upgrades the length if the length was shorter previously.
@return true if already indicated.
*/
bool checkAndSet(void* p, int len) {
unsigned x = mongoutils::hashPointer(p);
pair<void*, int>& nd = nodes[x % N];
if( nd.first == p ) {
if( nd.second < len ) {
nd.second = len;
return false; // haven't indicated this len yet
}
return true; // already indicated
}
nd.first = p;
nd.second = len;
return false; // a new set
}
private:
enum { N = Prime }; // this should be small the idea is that it fits in the cpu cache easily
pair<void*,int> nodes[N];
};
/** our record of pending/uncommitted write intents */
class IntentsAndDurOps : boost::noncopyable {
public:
vector<WriteIntent> _intents;
Already<127> _alreadyNoted;
vector< shared_ptr<DurOp> > _durOps; // all the ops other than basic writes
/** reset the IntentsAndDurOps structure (empties all the above) */
void clear();
void insertWriteIntent(void* p, int len) {
_intents.push_back(WriteIntent(p,len));
wassert( _intents.size() < 2000000 );
}
#if defined(DEBUG_WRITE_INTENT)
map<void*,int> _debug;
#endif
};
/** so we don't have to lock the groupCommitMutex too often */
class ThreadLocalIntents {
enum { N = 21 };
std::vector<dur::WriteIntent> intents;
bool condense();
public:
ThreadLocalIntents() : intents(N) { intents.clear(); }
~ThreadLocalIntents();
void _unspool();
void unspool();
void push(const WriteIntent& i);
int n_informational() const { return intents.size(); }
static AtomicUInt nSpooled;
};
/** A commit job object for a group commit. Currently there is one instance of this object.
concurrency: assumption is caller is appropriately locking.
for example note() invocations are from the write lock.
other uses are in a read lock from a single thread (durThread)
*/
class CommitJob : boost::noncopyable {
void _committingReset();
~CommitJob(){ verify(!"shouldn't destroy CommitJob!"); }
/** record/note an intent to write */
void note(void* p, int len);
// only called by :
friend class ThreadLocalIntents;
public:
SimpleMutex groupCommitMutex;
CommitJob();
/** note an operation other than a "basic write". threadsafe (locks in the impl) */
void noteOp(shared_ptr<DurOp> p);
vector< shared_ptr<DurOp> >& ops() {
dassert( Lock::isLocked() ); // a rather weak check, we require more than that
groupCommitMutex.dassertLocked(); // this is what really makes the below safe
return _intentsAndDurOps._durOps;
}
/** this method is safe to call outside of locks. when haswritten is false we don't do any group commit and avoid even
trying to acquire a lock, which might be helpful at times.
*/
bool hasWritten() const { return _hasWritten; }
public:
/** these called by the groupCommit code as it goes along */
void commitingBegin();
/** the commit code calls this when data reaches the journal (on disk) */
void committingNotifyCommitted() {
groupCommitMutex.dassertLocked();
_notify.notifyAll(_commitNumber);
}
/** we use the commitjob object over and over, calling reset() rather than reconstructing */
void committingReset() {
groupCommitMutex.dassertLocked();
_committingReset();
}
public:
/** we check how much written and if it is getting to be a lot, we commit sooner. */
size_t bytes() const { return _bytes; }
/** used in prepbasicwrites. sorted so that overlapping and duplicate items
* can be merged. we sort here so the caller receives something they must
* keep const from their pov. */
const vector<WriteIntent>& getIntentsSorted() {
groupCommitMutex.dassertLocked();
sort(_intentsAndDurOps._intents.begin(), _intentsAndDurOps._intents.end());
return _intentsAndDurOps._intents;
}
bool _hasWritten;
private:
NotifyAll::When _commitNumber;
IntentsAndDurOps _intentsAndDurOps;
size_t _bytes;
public:
NotifyAll _notify; // for getlasterror fsync:true acknowledgements
unsigned _nSinceCommitIfNeededCall; // for asserts and debugging
};
extern CommitJob& commitJob;
#if defined(DEBUG_WRITE_INTENT)
void assertAlreadyDeclared(void *, int len);
#else
inline void assertAlreadyDeclared(void *, int len) { }
#endif
}
}
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