BMC
The code for the NSDI'21 paper "BMC: Accelerating Memcached using Safe In-kernel Caching and Pre-stack Processing".
BibTex entry available here.
BMC (BPF Memory Cache) is an in-kernel cache for memcached. It enables runtime, crash-safe extension of the Linux kernel to process specific memcached requests before the execution of the standard network stack. BMC does not require modification of neither the Linux kernel nor the memcached application. Running memcached with BMC improves throughput by up to 18x compared to the vanilla memcached application.
Requirements
Linux kernel v5.3 or higher is required to run BMC.
Other software dependencies are required to build BMC and Memcached-SR (see Building BMC and Building Memcached-SR).
Build instructions
Building BMC
BMC must be compiled with libbpf and other header files obtained from kernel sources. The project does not include the kernel sources, but the kernel-src-download.sh and kernel-src-prepare.sh scripts automate the download of the kernel sources and prepare them for the compilation of BMC.
These scripts require the following software to be installed:
gpg curl tar xz make gcc flex bison libssl-dev libelf-dev
The project uses llvm and clang version 9 to build BMC, but more recent versions might work as well:
llvm-9 clang-9
Note that libelf-dev is also required to build libbpf and BMC.
With the previous software installed, BMC can be built with the following:
$ ./kernel-src-download.sh
$ ./kernel-src-prepare.sh
$ cd bmc && make
After BMC has been successfully built, kernel sources can be removed by running the kernel-src-remove.sh script from the project root.
Building Memcached-SR
Memcached-SR is based on memcached v1.5.19. Building it requires the following software:
clang-9 (or gcc-9) automake libevent-dev
Either clang-9 or gcc-9 is required in order to compile memcached without linking issues. Depending on your distribution, you might also need to use the -Wno-deprecated-declarations compilation flag.
Memcached-SR can be built with the following:
$ cd memcached-sr
$ ./autogen.sh
$ CC=clang-9 CFLAGS='-DREUSEPORT_OPT=1 -Wno-deprecated-declarations' ./configure && make
The memcached binary will be located in the memcached-sr directory.
Further instructions
TC egress hook
BMC doesn't attach the tx_filter eBPF program to the egress hook of TC, it needs to be attached manually.
To do so, you first need to make sure that the BPF is mounted, if it isn't you can mount it with the following command:
# mount -t bpf none /sys/fs/bpf/
Once BMC is running and the tx_filter program has been pinned to /sys/fs/bpf/bmc_tx_filter, you can attach it using the tc command line:
# tc qdisc add dev
clsact
# tc filter add dev
egress bpf object-pinned /sys/fs/bpf/bmc_tx_filter
After you are done using BMC, you can detach the program with these commands:
# tc filter del dev
egress
# tc qdisc del dev
clsact
And unpin the program with # rm /sys/fs/bpf/bmc_tx_filter
License
Files under the bmc directory are licensed under the GNU Lesser General Public License version 2.1.
Files under the memcached-sr directory are licensed under the BSD-3-Clause BSD license.
Cite this work
BibTex:
@inproceedings{265047,
title = {{BMC}: Accelerating Memcached using Safe In-kernel Caching and Pre-stack Processing},
author = {Yoann Ghigoff and Julien Sopena and Kahina Lazri and Antoine Blin and Gilles Muller},
year = 2021,
month = apr,
booktitle = {18th {USENIX} Symposium on Networked Systems Design and Implementation ({NSDI} 21)},
publisher = {{USENIX} Association},
pages = {487--501},
isbn = {978-1-939133-21-2},
url = {https://www.usenix.org/conference/nsdi21/presentation/ghigoff}
}
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