Revision 7103559f49b46b3287973045f741c0679e3e9e44 authored by Sagar Vemuri on 21 June 2018, 18:02:49 UTC, committed by Facebook Github Bot on 21 June 2018, 18:13:08 UTC
Summary: This PR extends the improvements in #3282 to also work when using Direct IO. We see **4.5X performance improvement** in seekrandom benchmark doing long range scans, when using direct reads, on flash. **Description:** This change improves the performance of iterators doing long range scans (e.g. big/full index or table scans in MyRocks) by using readahead and prefetching additional data on each disk IO, and storing in a local buffer. This prefetching is automatically enabled on noticing more than 2 IOs for the same table file during iteration. The readahead size starts with 8KB and is exponentially increased on each additional sequential IO, up to a max of 256 KB. This helps in cutting down the number of IOs needed to complete the range scan. **Implementation Details:** - Used `FilePrefetchBuffer` as the underlying buffer to store the readahead data. `FilePrefetchBuffer` can now take file_reader, readahead_size and max_readahead_size as input to the constructor, and automatically do readahead. - `FilePrefetchBuffer::TryReadFromCache` can now call `FilePrefetchBuffer::Prefetch` if readahead is enabled. - `AlignedBuffer` (which is the underlying store for `FilePrefetchBuffer`) now takes a few additional args in `AlignedBuffer::AllocateNewBuffer` to allow copying data from the old buffer. - Made sure not to re-read partial chunks of data that were already available in the buffer, from device again. - Fixed a couple of cases where `AlignedBuffer::cursize_` was not being properly kept up-to-date. **Constraints:** - Similar to #3282, this gets currently enabled only when ReadOptions.readahead_size = 0 (which is the default value). - Since the prefetched data is stored in a temporary buffer allocated on heap, this could increase the memory usage if you have many iterators doing long range scans simultaneously. - Enabled only for user reads, and disabled for compactions. Compaction reads are controlled by the options `use_direct_io_for_flush_and_compaction` and `compaction_readahead_size`, and the current feature takes precautions not to mess with them. **Benchmarks:** I used the same benchmark as used in #3282. Data fill: ``` TEST_TMPDIR=/data/users/$USER/benchmarks/iter ./db_bench -benchmarks=fillrandom -num=1000000000 -compression_type="none" -level_compaction_dynamic_level_bytes ``` Do a long range scan: Seekrandom with large number of nexts ``` TEST_TMPDIR=/data/users/$USER/benchmarks/iter ./db_bench -benchmarks=seekrandom -use_direct_reads -duration=60 -num=1000000000 -use_existing_db -seek_nexts=10000 -statistics -histogram ``` ``` Before: seekrandom : 37939.906 micros/op 26 ops/sec; 29.2 MB/s (1636 of 1999 found) With this change: seekrandom : 8527.720 micros/op 117 ops/sec; 129.7 MB/s (6530 of 7999 found) ``` ~4.5X perf improvement. Taken on an average of 3 runs. Closes https://github.com/facebook/rocksdb/pull/3884 Differential Revision: D8082143 Pulled By: sagar0 fbshipit-source-id: 4d7a8561cbac03478663713df4d31ad2620253bb
1 parent 524c6e6
make_package.sh
# shellcheck disable=SC1113
#/usr/bin/env bash
set -e
function log() {
echo "[+] $1"
}
function fatal() {
echo "[!] $1"
exit 1
}
function platform() {
local __resultvar=$1
if [[ -f "/etc/yum.conf" ]]; then
eval $__resultvar="centos"
elif [[ -f "/etc/dpkg/dpkg.cfg" ]]; then
eval $__resultvar="ubuntu"
else
fatal "Unknwon operating system"
fi
}
platform OS
function package() {
if [[ $OS = "ubuntu" ]]; then
if dpkg --get-selections | grep --quiet $1; then
log "$1 is already installed. skipping."
else
# shellcheck disable=SC2068
apt-get install $@ -y
fi
elif [[ $OS = "centos" ]]; then
if rpm -qa | grep --quiet $1; then
log "$1 is already installed. skipping."
else
# shellcheck disable=SC2068
yum install $@ -y
fi
fi
}
function detect_fpm_output() {
if [[ $OS = "ubuntu" ]]; then
export FPM_OUTPUT=deb
elif [[ $OS = "centos" ]]; then
export FPM_OUTPUT=rpm
fi
}
detect_fpm_output
function gem_install() {
if gem list | grep --quiet $1; then
log "$1 is already installed. skipping."
else
# shellcheck disable=SC2068
gem install $@
fi
}
function main() {
if [[ $# -ne 1 ]]; then
fatal "Usage: $0 <rocksdb_version>"
else
log "using rocksdb version: $1"
fi
if [[ -d /vagrant ]]; then
if [[ $OS = "ubuntu" ]]; then
package g++-4.8
export CXX=g++-4.8
# the deb would depend on libgflags2, but the static lib is the only thing
# installed by make install
package libgflags-dev
package ruby-all-dev
elif [[ $OS = "centos" ]]; then
pushd /etc/yum.repos.d
if [[ ! -f /etc/yum.repos.d/devtools-1.1.repo ]]; then
wget http://people.centos.org/tru/devtools-1.1/devtools-1.1.repo
fi
package devtoolset-1.1-gcc --enablerepo=testing-1.1-devtools-6
package devtoolset-1.1-gcc-c++ --enablerepo=testing-1.1-devtools-6
export CC=/opt/centos/devtoolset-1.1/root/usr/bin/gcc
export CPP=/opt/centos/devtoolset-1.1/root/usr/bin/cpp
export CXX=/opt/centos/devtoolset-1.1/root/usr/bin/c++
export PATH=$PATH:/opt/centos/devtoolset-1.1/root/usr/bin
popd
if ! rpm -qa | grep --quiet gflags; then
rpm -i https://github.com/schuhschuh/gflags/releases/download/v2.1.0/gflags-devel-2.1.0-1.amd64.rpm
fi
package ruby
package ruby-devel
package rubygems
package rpm-build
fi
fi
gem_install fpm
make static_lib
make install INSTALL_PATH=package
cd package
LIB_DIR=lib
if [[ -z "$ARCH" ]]; then
ARCH=$(getconf LONG_BIT)
fi
if [[ ("$FPM_OUTPUT" = "rpm") && ($ARCH -eq 64) ]]; then
mv lib lib64
LIB_DIR=lib64
fi
fpm \
-s dir \
-t $FPM_OUTPUT \
-n rocksdb \
-v $1 \
--prefix /usr \
--url http://rocksdb.org/ \
-m rocksdb@fb.com \
--license BSD \
--vendor Facebook \
--description "RocksDB is an embeddable persistent key-value store for fast storage." \
include $LIB_DIR
}
# shellcheck disable=SC2068
main $@
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