The latency test at tesmyinternetspeed.org provides exclusive result displaying the statistics about your bandwidth that is rare to find with other speed tests. You can check other test tools like upload test, ping test, download test, jitter test, latency test, wifi speed test, dsl speed test, broadband speed test with internet speed test tool. Latency is the amount of time it takes for a computer or application to respond to your request. The less time it takes the better. This is a test where you want to score low and there's a theoretical limit to how low you can go. Meaning the response was instant. Absolute zero is impossible on this test.

Check latency from 12415 locations worldwide. ICMP PING Traceroute DNS Page load Http Get. Random probes on current map view. Nov 11, 2020 The 1.4 version of DPC Latency Checker is provided as a free download on our website. This free software is an intellectual property of Thesycon GmbH. The most popular versions of the tool 1.4 and 1.3. The default filename for the program's installer is dpclat.exe. The software is included in System Utilities.

Contributors

Vish Viswanathan, Karthik Kumar, Thomas Willhalm, Patrick Lu, Blazej Filipiak, Sri Sakthivelu

Introduction

An 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. In a multi-socket system where Non-Uniform Memory Access (NUMA) is enabled, local memory latencies and cross-socket memory latencies will vary significantly. Besides latency, bandwidth (b/w) also plays a big role in determining performance. So, measuring these latencies and b/w is important to establish a baseline for the system under test, and for performance analysis.

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. 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.

Installation

Intel® MLC supports both Linux and Windows.

Linux

Copy the mlc binary to any directory on your system
Intel® MLC dynamically links to GNU C library (glibc/lpthread) and this library must be present on the system
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. Refer readme documentation on running without root privileges
MSR driver (not part of the install package) should be loaded. This can typically be done with 'modprobe msr' command if it is not already included.

Windows

Copy mlc.exe and mlcdrv.sys driver to the same directory. The mlcdrv.sys driver is used to modify the h/w prefetcher settings.

Previous releases of MLC s/w provided two sets of binaries (mlc and mlc_avx512). mlc_avx512 was compiled with newer tool chain to support AVX512 instructions while mlc binary supported SSE2 and AVX2 instructions. With MLC v3.7 release onwards, only one binary is provided which supports SSE2, AVX2 and AVX512 instructions. 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.

HW Prefetcher Control

It is challenging to accurately measure memory latencies on modern Intel processors as they have sophisticated h/w prefetchers. Intel® MLC automatically disables these prefetchers while measuring the latencies and restores them to their previous state on completion. The prefetcher control is exposed through MSR (Disclosure of Hardware Prefetcher Control on Some Intel® Processors) and MSR access requires root level permission. So, Intel® MLC needs to be run as ‘root’ on Linux. On Windows, we have provided a signed driver that is used for this MSR access. If Intel® MLC can’t be run with root permissions, please consult the readme.pdf that can be found in the download package.

What Does the Tool Measure

When the tool is launched without any argument, it automatically identifies the system topology and measures the following four types of information. A screen shot is shown for each.

1. A matrix of idle memory latencies for requests originating from each of the sockets and addressed to each of the available sockets

2. Peak memory b/w measured (assuming all accesses are to local memory) for requests with varying amounts of reads and writes

3. A matrix of memory b/w values for requests originating from each of the sockets and addressed to each of the available sockets

4. Latencies at different b/w points

It also measures cache-to-cache data transfer latencies.

Intel® MLC also provides command line arguments for fine grained control over latencies and b/w that are measured.

Here are some of the things that are possible with command line arguments:

Measure latencies for requests addressed to a specific memory controller from a specific core
Measure cache latencies
Measure b/w from a subset of the cores/sockets
Measure b/w for different read/write ratios
Measure latencies for random address patterns instead of sequential
Change stride size for latency measurements
Measure cache-to-cache data transfer latencies

How Does It Work

One of the main features of Intel® MLC is measuring how latency changes as b/w demand increases. To facilitate this, it creates several threads where the number of threads matches the number of logical CPUs minus 1. These threads are used to generate the load (henceforth, these threads will be referred to as load-generation threads). The primary purpose of the load-generation threads is to generate as many memory references as possible. While the system is loaded like this, the remaining one CPU (that is not being used for load generation) runs a thread that is used to measure the latency. This thread is known as the latency thread and issues dependent reads. Basically, this thread traverses an array of pointers where each pointer is pointing to the next one, thereby creating a dependency in reads. The average time taken for each of these reads provides the latency. Depending on the load generated by the load-generation threads, this latency will vary. Every few seconds the load-generation threads automatically throttle the load generated by injecting delays, thus measuring the latency under various load conditions. Please refer to the readme file in the package that you download for more details.

Command Line Arguments

Launching Intel® MLC without any parameters measures several things as stated earlier. However, with command line arguments, each of the following specific actions can be performed in sequence:

mlc --latency_matrix

prints a matrix of local and cross-socket memory latencies

mlc --bandwidth_matrix

prints a matrix of local and cross-socket memory b/w

mlc --peak_injection_bandwidth

prints peak memory b/w (core generates requests at fastest possible rate) for various read-write ratios with all local accesses

mlc --max_bandwidth

prints maximum memory b/w (by automatically varying load injection rates) for various read-write ratios with all local accesses

mlc --idle_latency

prints the idle memory latency of the platform

mlc --loaded_latency

prints the loaded memory latency of the platform

mlc --c2c_latency

prints the cache-to-cache transfer latencies of the platform

mlc -e

Latency Checker Tool

do not modify prefetcher settings

There are more options for each of the commands above. Those are documented in the readme file in more detail and can be downloaded

Change Log

Version 1.0

Initial release

Latency Checker Download

Version 2.0

Support for b/w and loaded latencies added

Version 2.1

Latency Checker Download

Launch 'spinner' threads on remote node for measuring better remote memory b/w
Automatically disable numa balancing support (if present) to measure accurate remote memory latencies

Version 2.2

Fixed a bug in topology detection where certain kernels were numbering the cpus differently. In those cases, consecutive cpu numbers were assigned to the same physical core (like cpus 0 and 1 are on physical