Ns2 project in New Jersey

    Ns2 project in New Jersey analysis that is performed by an individual sensor, which is then termed an extended sensor, reduces the sensor’s degree of interaction with its resident monitor, thereby reducing monitoring overhead. For simple ns2 project in New Jersey analyses that are relatively inexpensive compared to the cost of communication, extended sensors may be preferred. More complex analysis must be performed ns2 project in New Jersey elsewhere, so that needless perturbation of the  process being monitored is avoided. A second tradeoff involves computation within the resident monitor.

      If the analysis is performed ns2 project in New Jersey within a resident monitor, its interactions with the ns2 project in New Jersey central monitor are reduced. However, excessive analysis within a specific resident monitor may lead to an undue computational load and process switching overhead ns2 project in New Jersey being imposed on the same processor on which the application processes being monitored are executing. This may not be tolerable for certain multiprocessor or ns2 project in New Jersey real-time architectures , as shown below. Additional tradeoffs concern the central monitor.

       If the central ns2 project in New Jersey monitor does not perform analysis and simply forwards unanalyzed data to the agent that requires the monitoring information excessive communication may result between central monitor and the “user.” However, the agent itself may ns2 project in New Jersey decide what analyses should be performed; it retains complete freedom regarding the questions that may be asked about the data being collected Altematively, such freedom may ns2 project in New Jersey be sacrificed by performing analysis within the central monitor, thereby reducing the degree of interaction with the “user.”

Ns2 project in United Arab Emirates

      Ns2 project in United Arab Emirates the location of the resident monitor process in relation to the application process(es), either on the same processor or on a dedicated processor in the same multiprocessor. The cost of event record generation in the application process. The ns2 project in United Arab Emirates communication cost between the application process and the resident monitor, and between the resident and central monitors, expressed as a fixed overhead plus the cost per byte of event records sent.

       The ns2 project in United Arab Emirates latency constraint of evaluating the action predicate, as expressed in the CORRECTclause of the view. The notification latency constraint, as expressed in the WITHINns2 project in United Arab Emirates portion of the NOTIFYclause. The relationship between program variables referenced the ns2 project in United Arab Emirates action predicate of the view, specifically, whether one object or multiple objects are involved, the process or processor co-residency  of objects involved, an ns2 project in United Arab Emirates estimate of the selectivity of subexpressions in the action predicate, and the approximate evaluation cost for the target list and action predicate.

      Toillustrate ns2 project in United Arab Emirates the manner in which these considerations affect the decisions made during sensor generation, consider the distributed monitoring system in, consisting of ns2 project in United Arab Emirates sensors, probes, and central and resident monitors. In this system, ns2 project in United Arab Emirates the analysis of data being collected may be performed either by individual sensors, by the resident monitor, by the central monitor, or by any ns2 project in United Arab Emirates combination thereof. Several implementation tradeoffs result.One tradeoff is monitoring overhead versus communication ns2 project in United Arab Emirates cost.

Ns2 project in Saudi Arabia

      Ns2 project in Saudi Arabia important aspects like perturbation\ and latency may be expressed as constraints, rather than procedurally. This implies that programmers need not understand the details of information collection and analysis, of monitoring system setup and distribution, etc. However, it also ns2 project in Saudi Arabia requires that such declarative specifications be automatically mapped to the low level collection ns2 project in Saudi Arabia  and evaluation mechanisms discussed in by the monitoring system’s compiler. Such mappings must ensure that the information collection and analysis ns2 project in Saudi Arabia meet possibly stringent real-time constraints, while minimally perturbing the application as it executes. Fortunately, mappings may be varied along several dimensions.

        This ns2 project in Saudi Arabia section will describe how the monitoring system’s compiler may determine appropriate mappings. Where should each subexpression of the action predicate and the expressions ns2 project in Saudi Arabia in the target list be performed: in the relevant sensor, in the application code, in the resident monitor, or in the central monitor, Should ns2 project in Saudi Arabia ns2 project in Saudi Arabia the sensor send event records to the resident monitor, or directly to the central monitor How long should event records be queued in the application process, and in the ns2 project in Saudi Arabia resident monitor How long should notifications be queued Should notifications be generated only in the central monitor, or also in the resident monitor, or even in the application program, We emphasize that these decisions are not independent, and that ns2 project in Saudi Arabia some alternatives are not available for all views.

      For instance, if the action predicate mentions two attributes associated with objects residing on ns2 project in Saudi Arabia different processors served by separate resident monitors, then the analysis must be done in the central monitor, as neither the sensors nor the resident monitors have sufficient information .

Ns2 project in Iraq

         Ns2 project in Iraq note that the analysis phase of monitoring often requires the comparison of time fields among multiple events that may have occurred on ns2 project in Iraq different nodes of the distributed system. We have not explored any novel methods for event or time synchronization . For most of our applications, it has been ns2 project in Iraq sufficient to assume that processor clocks are synchronized to within tens of microseconds. In conclusion, views as defined above are useful for specifying dynamic monitoring for several reasons: The real-time attributes of program monitoring, such as maximum monitoring ns2 project in Iraq delays, etc., are easily specified.

         Performance specifications regarding monitoring are easily stated, which results in the generation of efficient collection and analysis using probes, extended sensors, and analysis code in resident and central monitors. In essence, the monitor ns2 project in Iraq can tailor its collection and analysis mechanisms to single applications or even single execution runs of applications. Language and system independence are achieved by ns2 project in Iraq expressing views in terms of attributes rather than in terms of program variables present ns2 project in Iraq in the application.

       In addition, any program described with the E-R model may be monitored, including operating system components and systems software for a ns2 project in Iraq more extensive discussion of language issues in the specification of monitoring. The attachment of graphical representations to monitoring views is the subject of other ns2 project in Iraq past and future research performed by our group. It should be apparent from the in the previous section that the attribute and view languages permit users to express application-dependent monitoring views in a high level, declarative fashion.

Ns2 project in Malaysia

        Ns2 project in Malaysia The CORRECTclause potentially further reduces monitoring perturbation by relaxing the timing constraints imposed ns2 project in Malaysia on the calculation of the active predicate. This clause allows users to express allowable tolerances in monitoring due to network delays and unsynchronized processor clocks. In this case, if the ns2 project in Malaysia queue size of each queue manager exceeded  within a window of, then the predicate is considered satisfied.

         If the CORRECTclause is omitted, then ns2 project in Malaysia the view is active only when both queue sizes are simultaneously4greater than The NOTIFYclause instructs the monitor to directly communicate in some manner ns2 project in Malaysia the new value  view’s attribute to the application or AC process at port address  on machine. eduwhenever the view becomes active. The maximum latency ns2 project in Malaysia of this notification can also be specified; here the process ns2 project in Malaysia expects to be notified within one second. Again, a long latency provides the monitor flexibility in reducing its overhead. Monitoring message traffic may be reduced by buffering values in user processes, resident monitors, or the central monitor.

    For example, the large value ns2 project in Malaysia specified here allows the central monitor to buffer ns2 projects in Malaysia multiple messages before performing a single message send to the AC with the buffered messages. One implementation used in our system simply “flushes” all buffers ns2 projects in Malaysia of any relevant resident monitors after some maximum permissible delay in reporting has occurred. If the NOTIFYclause is omitted, the monitor is instructed ns2 project in Malaysia to simply update the entry corresponding to the view’s attribute in the database when the view becomes active.

Ns2 project in Singapore

         Ns2 project in Singapore asindicated in, all attribute specifications are compiled into probes and into attributes of entities stored in the database. This is also the case for the attributes ofrelationships that can be monitored. Probe implementations ns2 project in Singapore are linked and loaded with the target application’s processes and resident monitors, and they are registered with the central monitor. Similar actions are taken for the sensor ns2 project in Singapore implementations and the analysis code derived from the view specifications explained next. Attributes that can be monitored constitute the basis from ns2 project in Singapore which the set of actual events to be monitored is drawn.

        That set is specified with the viewlanguageby programmers as a collection of monitoringviewsstated as entities, relationships, and sets ns2 project in Singapore in the database. The sample view below concerns the queue sizes of two QueueManagerobjects. The viewlanguagesyntax accepted by the ns2 project in Singapore prototype described later is similar to that ns2 project in Singapore appearing below. This view is defined to be activewhen the value of queue– Sizeis greater than 24 in both instantiations of QueueManager; this boolean expression on attributes is ns2 project in Singapore termed theACTIVEpredicate.

       When a view is active, the value of itsderived attributes, mentioned in the targetlistof the viewin this case, the target list consists of the single attributethisqueuesizecomputed by the expression QueueManager. are computed and made ns2 project in Singapore available by the monitor to other environment tools, such as the adaptation controller and the graphical display. Since the monitoring system need not collect, record, and ns2 project in Singapore display information at times at which the view is not active , the ACTIVE predicate reduces the amount of work themonitor must do, thereby reducing monitoring perturbation.

Ns2 project in jordan

       Ns2 project in Jordan regarding monitoring, the values of some attributes  may be supplied automatically by the parallel programming system. Other attributes must be defined by the programmer. For example, in the sample ns2 project in Jordan quicksort program, the user may wish to be notified when the size of the Queueobject exceeds some predefined threshold. In that case, the programmer’s monitoring specification ns2 project in Jordan would explicitly define the attribute queuesizeof the Queueobject. The queuesizeattribute may be mapped to a variable called “q-size” in the application’s code. However, ns2 project in jordan attributes may also be defined in terms of multiple variables used in the application program.

      In general, ns2 project in Jordan an attribute’s value is an expression over one or more variables. Attributes are typechecked by the PCS, through which the application was originally coded. again consider the Queueobject of the sample quicksort ns2 project in Jordan program. In order to evaluateworkload balancing among multiple processes performing thens2 project in Jordan sort of unsorted queue subranges, the user may wish to monitorthe attribute requestDurationfor ns2 project in Jordan each element of that queue.

     This attribute is not predefined and is not maintainedas a variable in the code and therefore, cannot be generated bythe PCS.Instead, such ns2 project in Jordan an attribute must be computed for each request from the source code variables beginRequestTime and endRequestTimewhich are maintained in the code in this case. Two ns2 project in jordan simple languages are used for the specification of program monitoring in the context of the E-R model: the attribute language and the view language. All nondefault, monitorable attributes of a parallel program must be explicitly defined with the attributelanguage.

Ns2 project in london

      Ns2 project in London specifically, in the Issos system, the program construction system generates an E-Rprogram description and records it in a main memory databaseaccessible to all system tools, based on the program’s languagens2 project in London specification and on its knowledge of the program’s run-time representation. Other system components The objective of this paper is not to describe and defend theE-R model, ns2 project in london the database supporting it, and their usefulness for tool integration.

      Elsewhere we provide details on the Issos system and describe a more efficient, persistent ns2 project in London anddistributed database implementation Other approaches to tool integration ns2 project in london also exist Here we simply describe a sample program represented with the E-R model, so that the reader may understand the monitor’s view of a parallel program. Consider a ns2 project in london parallel sort program like the various versions of parallel quicksort described in the literature .

             In the object-based Issos programming system, this program is represented ns2 project in London at run-time as objects interacting via invocation messages, much like the representation of distributed programs in Eden The sort program consists of several objects, including a Queue object which contains a process that maintains a queue of unsorted subranges of the ns2 project in london array being sorted and a Sort object which contains multiple internal processes performing the actual sorting of the array. While the Issos run-time system represents the ns2 project in London  program as a set of objects, the monitor views the program with the E-R model, thereby using ns2 project in London a description that is independent of the execution environment’s program representation. With the E-R model, this program.

Ns2 project in United States

       Ns2 project in United States however, note that\ post-execution analysis in our system is restricted to those queries that are possible to ns2 project in United States answer with the partially analyzed information contained in the database. Turn a particular sensor on or off. This operation is performed to trigger a sampled sensor, or to begin or end the trace of a specific program ns2 project in United States attribute, such as the values of one of its variables. The issuer of this command may request to be notified when a condition or set of conditions regarding the variable’s values becomes true. Probe the current value of a program attribute Retrieve the value of a program attribute which the monitor is or has been tracing.

         The value is ns2 project in United States retrievedfrom the monitor’s database. The next section presents a model of information for use by the monitoring system and shows that this model is an appropriate basis for monitoring specifications. Such specifications are compiled into efficient collection and analysis mechanisms that employ the operations just presented.

          In order to make the monitoring system independent of specific languages, compilers, operating systems, etc., we ns2 project in United States describe in terms of an abstract information model based on the information model  the programs for which monitoring is to be performed, the hardware and software environment in which the programs execute, the data to be collected, and ns2 project in United States the calculations to be performed.Our model includes typed entities, typed relationships between entities, and typed sets of both. The model can incorporate static information about parallel programs and about their execution environments , ns2 project in United States thus capturing compile- and load-time program information, hardware configuration, and others.

Ns2 project in Alberta

       Ns2 project in Alberta probes directly access the address spaces of individual processes on that node, thereby providing a convenient mechanism for amp ling.The main advantage of probes over sampled sensors is that the application code ns2 project in Alberta need not be changed for probing, so that the information to be probed may be defined dynamically. Furthermore, when monitoring parallel programs ns2 project in Alberta executing on shared memory machines, the use of probes versus sensors can reduce program perturbation due to monitoring Any monitoring system must address ns2 project in Alberta the storage of the program information it produces.

        Since the primary use of our monitor is dynamic monitoring, we first store all monitoring information in data structures mapped to main memory using the operating system’s virtual memory mechanisms, thereby reducing ns2 project in Alberta the latency of access to such information. For performance reasons, this ns2 project in Alberta collected data, termed the database, does not contain raw data. It contains analyzed data derived from the information collected using sensors and probes. All information stored in the database is tagged with time stamps and locations of occurrence, for use ns2 project in Alberta by dynamic and post-execution analysis of monitoring information.

     The data structures being used are straightforward template structures derived from the information model used for description of monitoring information. Although the virtual memory database can grow to significant size, for long-term persistent information storage, we currently use ad hoc ns2 project in Alberta file structures, but would prefer using a large-scale historical database in order to be able to perform efficient, additional post-execution analyses. Sample post-execution analysis of such stored information may concern additional analysis of interest to the ns2 project in Alberta programmer or the adaptation algorithms, or it may concern the reproduction or replay of program execution .