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Currently eviction is performed until occupancy of the whole region drops below the 85% threshold. This may take a while if region had high occupancy and is large. We could improve the situation by only evicting until occupancy of the sparsest segment drops below the threshold, as is done by this change. I tested this using a c-s read workload in which the condition triggers in the cache region, with 1G per shard: lsa-timing - Reclamation cycle took 12.934 us. lsa-timing - Reclamation cycle took 47.771 us. lsa-timing - Reclamation cycle took 125.946 us. lsa-timing - Reclamation cycle took 144356 us. lsa-timing - Reclamation cycle took 655.765 us. lsa-timing - Reclamation cycle took 693.418 us. lsa-timing - Reclamation cycle took 509.869 us. lsa-timing - Reclamation cycle took 1139.15 us. The 144ms pause is when large eviction is necessary. The change improves worst case latency. Reclamation time statistics over 30 second period after cache fills up, in microseconds: Before: avg = 1524.283148 stdev = 11021.021118 min = 12.934000 max = 144356.000000 sum = 257603.852000 samples = 169 After: avg = 1317.362414 stdev = 1913.542802 min = 263.935000 max = 19244.600000 sum = 175209.201000 samples = 133 Refs #1634. Message-Id: <1484730859-11969-1-git-send-email-tgrabiec@scylladb.com>
Scylla
Building Scylla
In addition to required packages by Seastar, the following packages are required by Scylla.
Submodules
Scylla uses submodules, so make sure you pull the submodules first by doing:
git submodule init
git submodule update --init --recursive
Building and Running Scylla on Fedora
- Installing required packages:
sudo dnf install yaml-cpp-devel lz4-devel zlib-devel snappy-devel jsoncpp-devel thrift-devel antlr3-tool antlr3-C++-devel libasan libubsan gcc-c++ gnutls-devel ninja-build ragel libaio-devel cryptopp-devel xfsprogs-devel numactl-devel hwloc-devel libpciaccess-devel libxml2-devel python3-pyparsing lksctp-tools-devel protobuf-devel protobuf-compiler systemd-devel libunwind-devel
- Build Scylla
./configure.py --mode=release --with=scylla --disable-xen
ninja-build build/release/scylla -j2 # you can use more cpus if you have tons of RAM
- Run Scylla
./build/release/scylla
- run Scylla with one CPU and ./tmp as data directory
./build/release/scylla --datadir tmp --commitlog-directory tmp --smp 1
- For more run options:
./build/release/scylla --help
Building Fedora RPM
As a pre-requisite, you need to install Mock on your machine:
# Install mock:
sudo yum install mock
# Add user to the "mock" group:
usermod -a -G mock $USER && newgrp mock
Then, to build an RPM, run:
./dist/redhat/build_rpm.sh
The built RPM is stored in /var/lib/mock/<configuration>/result directory.
For example, on Fedora 21 mock reports the following:
INFO: Done(scylla-server-0.00-1.fc21.src.rpm) Config(default) 20 minutes 7 seconds
INFO: Results and/or logs in: /var/lib/mock/fedora-21-x86_64/result
Building Fedora-based Docker image
Build a Docker image with:
cd dist/docker
docker build -t <image-name> .
Run the image with:
docker run -p $(hostname -i):9042:9042 -i -t <image name>