Home Tech AMD is preparing an extension of “Instruction-Based Sampling” Zen 4 IBS for...

AMD is preparing an extension of “Instruction-Based Sampling” Zen 4 IBS for Linux


AMD recently introduced the company’s qualifying instruction-based (IBS) capabilities for use in Linux perf subsystem and utility. This is a new presentation of the company – the first official patch for Zen 4 series processors.

Sampling support based on instructions for future AMD Zen 4 processors under Linux

The previous and current series of patches for the new AMD Zen 4 family had basic and vague terminology. With the latest fixes under consideration, users can be confident that support for Zen 4 Linux is now coming into effect and will be evident in brand new patches and updates to the open source operating system.

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Zen 4 is designed to improve instruction-based sampling by creating additional data source enhancements and a new ability to filter out Layer 3 cache misses.

The new features of Zen 4 IBS commented on the modifications with higher priority:

The DataSrc extension provides additional information about the data source for the specified download / store operations. Add support for these new bits in perf report / script raw-dump.

Filtering IBS L3 misses works by indicating an instruction to overflow the IBS counter and generating an NMI if the specified instruction causes an L3 miss. Samples without L3 miss are discarded, and the counter is reset with a random value (between 1-15 for pmu sampling and 1-127 for op pmu). This helps to reduce the overhead of the sample if the user is only interested in such samples. One way to use such filtered samples is to feed data to the page migration daemon in multilevel memory systems.

Add support for L3 miss filtering in the IBS driver via the new pmu attribute “l3missonly”.

Linux users will be able to read mailing list on the official Linux kernel website for new information on Zen 4 IBS patches.

Thus, outside of sampling based on perf instructions, the new feed for selection is also useful for gradually increasing the number of functions to compile to enable the transfer of sampling results to perf compiler hardware to aid in profile-based design. and optimized binaries. Intel has been more aggressive with functional and hardware performance counters developed under the future Linux operating system. Along with using for profiling possible optimizations and problems that require debugging, the inclusion by AMD of their IBS Zen 4 capabilities is great for the company.

Source: Phoronix


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