Speculative execution is an optimization technique where a computer system performs some task that may not be needed. Work is done before it is known whether it is actually needed, so as to prevent a delay that would have to be incurred by doing the work after it is known that it is needed.
What is speculative execution explain with the help of an example?
Speculative execution is a technique used by modern CPUs to speed up performance. The CPU may execute certain tasks ahead of time, “speculating” that they will be needed. … For example, the Meltdown security vulnerability affects some Intel CPUs due to a flaw in their speculative execution.
Does ARM have speculative execution?
On impacted processors, Arm says that while computing operations in advance part of the speculative execution process, when there’s a change in the Arm CPU’s instruction control flow, the CPU reacts by executing instructions found linearly in its memory, past the change in the control flow — an unwanted scenario.
What is the primary advantage of speculative execution?
Along with multiple branch prediction (used to predict the instructions most likely to be needed in the near future) and dataflow analysis (used to align instructions for optimal execution, as opposed to executing them in the order they came in), speculative execution delivered a dramatic performance improvement over …
Can Spectre and Meltdown be exploited remotely?
Researchers from Graz University of Technology, including one of the original Meltdown discoverers, Daniel Gruss, have described NetSpectre: a fully remote attack based on Spectre. With NetSpectre, an attacker can remotely read the memory of a victim system without running any code on that system.
Who discovered Spectre and Meltdown?
Spectre was independently discovered and reported by two people: Jann Horn (Google Project Zero) and.
How the Spectre and Meltdown hacks really worked?
Meltdown, Spectre, and their variants all follow the same pattern. First, they trigger speculation to execute code desired by the attacker. This code reads secret data without permission. Then, the attacks communicate the secret using Flush and Reload or a similar side channel.
Why speculative execution is important in Hadoop environment in particular?
Hadoop MapReduce Speculative execution is beneficial in some cases because in a Hadoop cluster with 100s of nodes, problems like hardware failure or network congestion are common and running parallel or duplicate task would be better since we won’t be waiting for the task in the problem to complete.
Why is speculative execution important in Hadoop?
The main goal of the speculative execution is to reduce job execution time. But this will come at the cost of the Hadoop cluster efficiency. On a busy Hadoop cluster, this may reduce the overall throughput because the redundant tasks are being executed in order to reduce the execution time for the single job.
What is speculative execution in hive?
In simple words, a speculative execution means that Hadoop in overall doesn’t try to fix slow tasks as it is hard to detect the reason (misconfiguration, hardware issues, etc), instead, it just launches another parallel/backup task for each task that is performing slower than the expected, on faster nodes.
Which of the following allows speculative execution?
8. Which of the following allows speculative execution? Explanation: The direct mapped cache has the advantage of allowing a simple and fast speculative execution.
What is the purpose of speculative execution Why is it usually restricted to the map phase?
The goal of speculative execution is to reduce job’s response time. But on a busy cluster it may affect the overall throughput of data and wastage of cluster resources.
What is speculative execution delaying execution?
Speculative execution in Hadoop MapReduce is an option to run a duplicate map or reduce task for the same input data on an alternative node. This is done so that any slow running task doesn’t slow down the whole job.
Is Spectre patched?
While patched systems are protected against Spectre, the nature of Spectre patches and the resulting impact on performance means that a large number of systems have not been patched.. That leaves many key systems vulnerable to Spectre. Worse, a new publicly accessible exploit for Spectre has just been published.
Are AMD processors affected by Spectre or Meltdown?
The Meltdown flaw, also called Spectre variant 3, affected both Intel and ARM CPUs. … Spectre affects virtually all out-of-order CPUs that use speculative execution to increase performance, including AMD and Arm’s processors.
What did Project Zero found out in today’s CPU?
Last year, Google’s Project Zero team discovered serious security flaws caused by “speculative execution,” a technique used by most modern processors (CPUs) to optimize performance.
Does CPU affect Meltdown and Spectre?
Meltdown mostly affects Intel processors and at the moment, it is unclear whether AMD processors are also affected. ARM says some of its processors are also affected. Spectre is much more widespread, however. Almost every system is affected by Spectre, including desktops, laptops, cloud servers, and even smartphones.
What is Meltdown and Spectre vulnerabilities?
In the most basic definition, Spectre is a vulnerability allowing for arbitrary locations in the allocated memory of a program to be read. Meltdown is a vulnerability allowing a process to read all memory in a given system.
What is meant by superscalar execution?
A superscalar processor allows multiple unrelated instructions to start on the same clock cycle on separate hardware units or pipelines. …
Is arm out of order execution?
According to Wikipedia, the Cortex-A9 uses out-of-order execution, whereas the Cortex-A8 does not; however, both implement the same ARM architecture (ARMv7-A).
How is branch prediction related to speculative execution?
Branch prediction is done by the processor to try to determine where the execution will continue after a conditional jump, so that it can read the next instruction(s) from memory. Speculative execution goes one step further and determines what the result would be from executing the next instruction(s).