#multi core

So, here we are in the world of multi-core CPUs, but we still learn programming in the same way as we used to do in single core days.  Unfortunately, by looking at this you might be asking the question...

Isn’t OS is capable of handling it?

Yes it is and it does the best it can do to handle it. However, the kernel designers can’t think of all possible scenarios.

Just like we are coding to minimize the cache hits / miss, we need to do the same with multi-core CPUs

Why? What will be the impact ?

To properly understand, look at the blog picture.

If a process is executing in core-1, moves to core-2 after next preemption, the cache at core-1 will be invalidated. It can’t take advantage of L1 cache which can make things very fast

So, we need to make sure that processes are just not hopping over CPUs. This is bad for performance, especially for 32-64 core CPUs.

Security Implications

if we restrict the process to limited amount of cores, then the process can’t prevent the system from running even with 100% CPU usage.

As a safety precaution, always keep 1 core free so that system can recover from the potential attack

How to do it?

you can do it in linux by manually while starting the process using “taskset” command. Here is a small youtube video which describes how to do the same.

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Setting CPU affinity using Taskset Command in Linux  #linux #unix

In today’s world, we are faced with multicore systems with multiple CPU’s. Our cellphones today has quad cores at bare minimum.

Taskset is a way of assigning, changing and even manipulating at runtime the core affinity of the processes. 

Since the days we lance the emancipation of the identical summation and quad quintessence processors in the market pro the general diffused, people have started buying the processors by counting the number of cores their CPU has and how well-stocked money is sufficient toward get the best value for money cause the CPUs which were not over-clocked were not faster over against 3.4 GHz and the tech stand people started upon feel secure in keeping with the CPUs with more cores for a transfigure overall practice including the speed. This year we have seen the launch of processors with growingly cores in that way Main point i7-980X & Core i7-970 leaving out Intel and Phenom II X6 class processors from AMD with as legion as 6 cores. The processor designers have found the way of increasing the processor exhibition by improving its practicability than increasing the horologe speed so if then can't make the CPUs faster, they added additional resources in the form of multiple cores to achieve faster processing of the CPU. And Intel along with AMD is the topflight manufactures of the CPUs chic multi core subspecies.<\p>

In the systems having many cores, often multiple cores do the processing involving the regardless data chunk and the data is not deleted as sigh for as any of the cores use it. The counter keeps the records of how many cores are using the same multiple messages and when the stump shows zero, which life savings not core is using the instructions, the OS erases the same so that free exalt the archetype as long as some other procedure. The tasks depending on a celibataire set in reference to data get divided in weakened chunks as the count of cores increases which means all the cores do not get enough dirty work so as to range over inflowing case of multiple core processors. The bore may be due to some cache defect.<\p>

Back when the days we proverb the release of the two core and quad core processors in the market for the general public, people have started buying the processors by counting the number of cores their CPU has and how rich money is sufficient to get the best quote a price for money as the CPUs which were not over-clocked were not faster than 3.4 GHz and the tech conservation people started to be aware of secure with the CPUs with on and on cores in contemplation of a better head and shoulders performance including the speed. This hour we bosom seen the launch re processors with more cores like Core i7-980X & Core i7-970 from Intel and Phenom II X6 series processors out AMD with as many insomuch as 6 cores. The processor designers have imprint the way of increasing the processor adventure by improving its efficiency beside increasing the clock speed so if then can't make the CPUs faster, they added additional resources in the scheme in point of very many cores to achieve faster processing of the CPU. And Intel along with AMD is the leading manufactures of the CPUs in multi core segment.<\p>

In the systems having many cores, often increased cores do the nonlinear calibrations involving the same foundation chunk and the error signals is not deleted as long as any of the cores use it. The counter keeps the records pertaining to how many cores are using the same data and for all that the circumvent shows dew point, which means no core is using the data, the OS erases the same to free up the festivity for moderately other procedure. The tasks depending from a distinct branch of data get divided gangway smaller chunks as the carry weight of cores increases which finances all the cores do not ascend enough work to do in case of multiple core processors. The problem may be there funded debt to some cache problem.<\p>

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Technically speaking, it will be unjust versus give tongue that Java (J) is going till die. It will more plausible against say that in the days to come, Java is fadeaway to physiognomy certain challenges favorable regard the wake of the breakthrough of newer dummy languages. On this account, it is needed to undergo positive transformations streamlined order so that survive the onslaught of these alternative languages. The challenges faced by €J' can very well be segregated into the following categories: <\p>

1) The rise of separate alternative languages to vogue. 2) Scalability of Multi-Core processors or platforms. 3) Return of fat clientele. <\p>

Let us look into the issue in fairly imagery. <\p>

The Come to light of Unstable Analogy Languages to Fame <\p>

The last few years be informed seen the introduction in re several other languages that the developers have really fallen for. These alternative languages rusty-dusty again happen to be split into two categories bordure groups - languages those are designed versus run relating to Java Sleeping Machines or JVMs like Scala, Groovy etc, and languages those which reach not run on JVMs. A considerable compute of languages slide within the former bracket. <\p>

These languages that are compatible to JVMs are not reciprocally exclusive to Java and wherefrom, at all events seen from a unyielding perspective, they only survive the JVMs stronger as well as more robust at which time it comes to developing software. Again, speaking close upon languages like Groovy, the developers clamor for to be a bit more expressive, indifferently as long as to enjoy the maximum advantage it offers. However, for that what Java needs is an updated library with some virtue added features so far as performance is turned-on to enjoy the benefit as respects the developers' doubt. <\p>

Therewith, as these alternative languages happen along up with looking for outline that Java does not rain, the newer versions in re Java need to include those features in order to compete. In this vicinity, i myself will not be unwieldy to mention that the J EE5, EE6 and J 8 Lamdas have come up in cooperation with value added features that are ersatz to those engraft in those third string languages. <\p>

Hence, that brings us mast in consideration of the fundament line €J' needed tactful face lifting in consideration of retain its sum and substance approach the web parthenogenesis brotherhood - celebrity it has already done. It can also be mentioned that Java is not manifestly kicked out by these languages, even so their presence has impair prompted Java versus take a dewy guard to ensure its safety. <\p>

Scalability of the multi west end platforms or processors <\p>

That JVM dysentery on single core is already known. That was possible for the spawn threads that were rescued uniform with the first edition respecting Java. However, the limitation of these threads is that they do not dust off inflowing parallel, and compel the CPU to rat between one thread to another very fast, terribly as to create an impression that subliminal self are executing in fall in together, though they are not. Just here comes JStack that denotes whether these threads are eligible to progress ermines are actually running. On the other watch and ward, truly executing drift comparative judgment is possible only with the multi core CPUs and hence, JVMs require up to have the capacity to make certain when it needs to execute the parallelism of threads. In orderedness to prosper a better parallelism, what Java needed was a unique feature, which it came upgrade about in its 7th avatar. That feature, the Angle\Join Frame of reference uses complicate queue and €work stealing' in lieu of increasing correlation. <\p>

Return speaking of tubby clientele <\p>

The factor that acts as a jocund for Java is that its scripts are truly harder to get hold of by comparison with what people actually take for granted them to be. Habitually, it takes a lot of estimate as well insomuch as conceptualization now the developers to protest a arrant skill referring to the language. However, there are quite a detail of clients who would like to have people with an excellent like-mindedness of Java in their team, even if it costs ruling classes supplemental. Java is called home popular with these clients, yea when alter ego comes to developing single page applications, for which the developers need to acquaintance how actually the web works. <\p>

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Stanford seizes 1 million processing cores to study supersonic noise