Meltdown and Spectre bugs: Difference between revisions

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Meltdown and Spectre are bugs related to speculative execution in a variety of CPU architectures developed during the past ten to fifteen years and which affect in particular processors from Intel and AMD, including those in use on Compute Canada clusters. A detailed discussion of the two bugs can be found on [https://arstechnica.com/gadgets/2018/01/meltdown-and-spectre-every-modern-processor-has-unfixable-security-flaws/ this page] and Compute Canada personnel are currently patching systems deemed sensitive to this vulnerability. What sort of performance degradation users will observe as a consequence of the patches is dependent on the software you are using and how it interacts with the operating system but in general the more filesystem activity and other input/output operations that a program performs during its execution, the more likely it is to suffer from a slowdown. Some benchmarks of the performance loss for AI and machine learning codes are publicly [https://medium.com/implodinggradients/meltdown-c24a9d5e254e available] and we recommend that users consider running some simple tests of their own to see if there is any substantial loss of performance with their own code(s).
Meltdown and Spectre are bugs related to speculative execution in a variety of CPU architectures developed during the past ten to fifteen years and which affect in particular processors from Intel and AMD, including those in use on Compute Canada clusters. A detailed discussion of the two bugs can be found on [https://arstechnica.com/gadgets/2018/01/meltdown-and-spectre-every-modern-processor-has-unfixable-security-flaws/ this page]. Compute Canada personnel are currently patching systems deemed sensitive to this vulnerability.  


== What are the impacts ? ==
== What are the impacts ? ==
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=== Performance impacts ===
=== Performance impacts ===
Many groups around the world, including within Compute Canada, are running various benchmarks. Certain figures that have been cited are alarming (up to a 30% or even 50% performance hit), while others are very minimal. Programs which do a lot of input/output (reading and writing files) seem to be most heavily affected by the patches released thus far. Examples of such software include databases or performing a file transfer (e.g. rsync). In general a typical high performance computing job should not be affected nearly as much since the vast majority of the runtime is spent computing rather than doing input and output. Different processor generations are also affected to different degrees, with older processors being those with the most notable performance degradation. If you suspect your jobs may incur a large performance penalty, we recommend that you compare its performance before and after. You can also contact our [[Technical support]] to get help, but keep in mind that code modification may be required to lessen the performance impact on any given code.  
Many groups around the world, including within Compute Canada, are running benchmarks to evaluate the effects of the operating system patches on performance. Certain figures that have been cited are alarming (up to a 30% or even 50% performance hit), while others are very minimal.


Below, you will find various links pointing to performance benchmarks. Keep in mind that those were not necessarily run on hardware and operating system similar to what Compute Canada clusters are running.
Tasks which involve a lot of input/output (reading and writing files) seem to be most heavily affected. Examples include databases, or file transfers (e.g. rsync). Most high performance computing jobs should be minimally affected since the vast majority of the run time is spent computing rather than doing input and output. Different processor generations are also affected to different degrees, with the most notable performance degradation reported for older processors. If you suspect your jobs may incur a large performance penalty, we recommend that you compare its performance before and after. (Naturally, this will only be useful if you have performance measurements which were taken before the patches were applied.) You can also contact our [[Technical support]] to get help, but keep in mind that code modification may be required to lessen the performance impact on any given code.
 
Below, you will find various links pointing to performance benchmarks. Keep in mind that those were not necessarily run on hardware and operating systems similar to what Compute Canada clusters are running.


== What is Compute Canada doing about it ? ==
== What is Compute Canada doing about it ? ==
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