Kpart

KPart

KPart is a tool for partitioning the last-level cache (LLC) dynamically between co-running applications on an Intel multicore processor with <i>way-partitioning</i> support. KPart is designed to sidestep a key limitation of way-partitioning: coarse-grained partition sizes.

KPart profiles the cache needs of co-running applications periodically, then groups the applications based on their cache profiles into clusters and maps cache partitions to these clusters. Applications within a cluster share their assigned partition, while applications across clusters remain isolated. More details on how profiling, clustering, and cache assignments are done are available in our HPCA'18 paper.

Platform

KPart was developed and tested on an 8-core Intel Broadwell D-1540 processor which supports LLC way-partitioning. The system was running Ubuntu 14.04, Linux kernel version 4.2.3. The LLC size is 12MB and supports up to 12 partitions, each of size 1MB.

Prerequisites

KPart requires the following libraries:

• perfmon2: Performance Monitoring on Linux
• armadillo: C++ Linear Algebra Library
• Make sure Cache Allocation Technology (CAT) and Cache Monitoring Technology (CMT) are supported, otherwise the tools under kpart/lltools/cat will not be able to monitor or partition the shared cache.

Building KPart

• Step 1: Build the libraries needed to access Intel's CAT and CMT features (under /kpart/lltools):

kpart$ cd lltools 
kpart/lltools$ make 

• Step 2: Update the LIBPFMPATH path in the Makefile under /kpart/src/ to point to your local LIBPFMPATH directory, then build KPart:

kpart$ cd src 
kpart/src$ make 

Running KPart

Usage: ./kpart_cmt <comma-sep-events> <phase_len> <logfile/- for stdout> <warmup_period_B> <profile_period_B>-- <max_phases_1> <input_redirect_1/'-' for stdin>  <comma-sep-core-list> prog1 -- ...

Test Example

A testing script is available under kpart/tests/example.sh. The simple script is designed to demonstrate how to invoke KPart. It runs multiple copies of a microbenchmark app which traverses an array (available under kpart/lltools), then profiles their cache needs and partitions the last-level cache among them using KPart.

Intel Bug with LLC partition numbers 10, 11

We found that in Intel Broadwell D-1540 processor, the LLC partitions numbered 10 and 11 cannot be mapped to two different classes of service (COS); i.e. any COS mapping that includes one of these partitions will automatically include the other partition as well. Therefore, when assigning partitions to classes of service on this processor model, one must make sure that 10 and 11 are always assigned to the same COS.

Contributors

• Nosayba El-Sayed, CSAIL MIT/QCRI, HBKU
• Harshad Kasture, Oracle
• Anurag Mukkara, CSAIL MIT
• Daniel Sanchez, CSAIL MIT
• Po-An Tsai, CSAIL MIT

Publication

El-Sayed, Mukkara, Tsai, Kasture, Ma, and Sanchez, KPart: A Hybrid Cache Partitioning-Sharing Technique for Commodity Multicores, HPCA-24, Austria, 2018.

License

This project is licensed under the MIT License - see the LICENSE file for details