net_instaweb::SharedMemVariable Class Reference

#include "shared_mem_statistics.h"

Inheritance diagram for net_instaweb::SharedMemVariable:

Public Member Functions
	SharedMemVariable (StringPiece name, Statistics *stats)
virtual StringPiece	GetName () const
Public Member Functions inherited from net_instaweb::MutexedScalar
int64	Get () const
void	Set (int64 value)
int64	SetReturningPreviousValue (int64 value)
int64	AddHelper (int64 delta)

Protected Member Functions
virtual AbstractMutex *	mutex () const
virtual int64	GetLockHeld () const
	Get/Setters that may only be called if you already hold the mutex.
virtual int64	SetReturningPreviousValueLockHeld (int64 value)
Protected Member Functions inherited from net_instaweb::MutexedScalar
void	SetLockHeld (int64 value)
int64	AddLockHeld (int64 delta)

Friends
class	SharedMemStatistics
class	SharedMemTimedVariable

Detailed Description

An implementation of Statistics using our shared memory infrastructure. These statistics will be shared amongst all processes and threads spawned by our host. Note that we will be obtaining a per-variable mutex for every read and write to these variables. Since this may be expensive, we may need each thread to keep a local cache and infrequently write through to this Statistics object.

Todo:

TODO(abliss): actually do this.

Because we must allocate shared memory segments and mutexes before any child processes and threads are created, all AddVariable calls must be done in the host before it starts forking/threading. Once all variables are added, you must call InitVariables(true), and then InitVariables(false) in every kid.

If a variable fails to initialize (due to either its mutex or the shared memory segment not working), it will not increment in that process (and a warning message will be logged). If the variable fails to initialize in the process that happens to serve a statistics page, then the variable will show up with value -1.

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The documentation for this class was generated from the following file:

• pagespeed/kernel/sharedmem/shared_mem_statistics.h