It also measures cache-to-cache data transfer latencies. A matrix of memory b/w values for requests originating from each of the sockets and addressed to each of the available sockets Peak memory b/w measured (assuming all accesses are to local memory) for requests with varying amounts of reads and writesģ. A matrix of idle memory latencies for requests originating from each of the sockets and addressed to each of the available socketsĢ. When the tool is launched without any argument, it automatically identifies the system topology and measures the following four types of information. If Intel® MLC can’t be run with root permissions, please consult the readme.pdf that can be found in the download package. On Windows, we have provided a signed driver that is used for this MSR access. So, Intel® MLC needs to be run as ‘root’ on Linux. The prefetcher control is exposed through MSR ( Disclosure of Hardware Prefetcher Control on Some Intel® Processors) and MSR access requires root level permission. Intel® MLC automatically disables these prefetchers while measuring the latencies and restores them to their previous state on completion. It is challenging to accurately measure memory latencies on modern Intel processors as they have sophisticated h/w prefetchers. By default AVX512 instructions won’t be used whether the processor supports it or not unless -Z argument is added explicitly to the command line. With MLC v3.7 release onwards, only one binary is provided which supports SSE2, AVX2 and AVX512 instructions. mlc_avx512 was compiled with newer tool chain to support AVX512 instructions while mlc binary supported SSE2 and AVX2 instructions. Previous releases of MLC s/w provided two sets of binaries (mlc and mlc_avx512). The mlcdrv.sys driver is used to modify the h/w prefetcher settings. Copy mlc.exe and mlcdrv.sys driver to the same directory.This can typically be done with 'modprobe msr' command if it is not already included. MSR driver (not part of the install package) should be loaded.Refer readme documentation on running without root privileges Root privileges are required to run this tool as the tool modifies the H/W prefetch control MSR to enable/disable prefetchers for latency and b/w measurements.Intel® MLC dynamically links to GNU C library (glibc/lpthread) and this library must be present on the system.Copy the mlc binary to any directory on your system.Intel® MLC supports both Linux and Windows*. New option -memory_bandwidth_scan (supported only on Linux*) to be able to measure memory bandwidth over the entire address range in 1 GB chunks.Support for 3rd Generation Intel® Xeon® Scalable Processors.It also provides several options for more fine-grained investigation where b/w and latencies from a specific set of cores to caches or memory can be measured as well. Intel® Memory Latency Checker (Intel® MLC) is a tool used to measure memory latencies and b/w, and how they change with increasing load on the system. So, measuring these latencies and b/w is important to establish a baseline for the system under test, and for performance analysis. Besides latency, bandwidth (b/w) also plays a big role in determining performance. In a multi-socket system where Non-Uniform Memory Access (NUMA) is enabled, local memory latencies and cross-socket memory latencies will vary significantly. Vish Viswanathan, Karthik Kumar, Thomas Willhalm, Patrick Lu, Blazej Filipiak, Sri Sakthivelu IntroductionĪn important factor in determining application performance is the time required for the application to fetch data from the processor’s cache hierarchy and from the memory subsystem.
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