58 lines
2.9 KiB
Markdown
58 lines
2.9 KiB
Markdown
# Low Level Memory Benchmark
|
|
|
|
These are the results of a low level memory benchmark (written in C) on my [laptop](../architecture/README.md)
|
|
|
|
## Summary plots (details below)
|
|
|
|
|
|
|
|
## Benchmarks details:
|
|
|
|
- Bandwidth (read), [bw_mem_rd](http://lmbench.sourceforge.net/man/bw_mem_rd.8.html). Allocate the specified amount of memory, zero it, and then time the reading of that memory as a series of integer loads and adds. Each 4-byte integer is loaded and added to accumulator.
|
|
|
|
[Results](t14-bwr.csv) (block size in MB, bandwith in MB/s)
|
|
- Bandwidth (write),[bw_mem](http://lmbench.sourceforge.net/man/bw_mem.8.html). Allocate twice the specified amount of memory, zero it, and then time the copying of the first half to the second half.
|
|
|
|
[Results](t14-bww.csv) (block size in MB, bandwith in MB/s)
|
|
- Latency (sequential access), [lat_mem_rd](http://lmbench.sourceforge.net/man/lat_mem_rd.8.html). Run two nested loops. The outer loop is the stride size of 128 bytes. The inner loop is the block size. For each block size, create a ring of pointers that point backward one stride. Traverse the block by `p = (char **)*p` in a for loop and time the load ladency over block.
|
|
|
|
[Results](t14-lseq.csv) (block size in MB, latency in ns)
|
|
- Latency (random access). Like above, but with a stride size of 16 bytes.
|
|
|
|
[Results](t14-lrnd.csv) (block size in MB, latency in ns)
|
|
|
|
## Running the benchmarks on Linux:
|
|
- You need the [lmbench](http://lmbench.sourceforge.net/) library and [cpuset](https://github.com/SUSE/cpuset)
|
|
- All commands must be run as root after having killed as many processes/services as possible, so that the CPUs are almost idle
|
|
- Disable address space randomization:
|
|
```bash
|
|
echo 0 > /proc/sys/kernel/randomize_va_space
|
|
```
|
|
- Set scaling governor to performance for CPU0:
|
|
```bash
|
|
echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
|
|
```
|
|
- Reserve CPU 0 fro our benchmark, i.e. kick out (almost) all other processes
|
|
```bash
|
|
cset shield --cpu 0 --kthread=on
|
|
```
|
|
- If you are on INTEL and CPU0 is part of a SMT-pair (hyperthreading), disable the peer
|
|
```bash
|
|
echo 0 > /sys/devices/system/cpu/cpu1/online
|
|
```
|
|
- Disable turbo mode on INTEL:
|
|
```bash
|
|
echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
|
|
```
|
|
- Run the configuration script for lmbench. Select only the `HARDWARE` set of benchmarks and set the maximum amount of memory to something like 1024MB
|
|
```bash
|
|
cd /usr/lib/lmbench/scripts
|
|
# the following command will create the configuration file /usr/lib/lmbench/bin/x86_64-linux-gnu/CONFIG.<hostname>
|
|
cset shield --exec -- ./config-run
|
|
# run the benchmark
|
|
cset shield --exec -- /usr/bin/lmbench-run
|
|
# results are in /var/lib/lmbench/results/x86_64-linux-gnu/<hostname>
|
|
```
|
|
|
|
|