Difference between revisions of "Improve pacman performance"

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=== pacget (aria2) Mirror Script ===
 
=== pacget (aria2) Mirror Script ===
  
This script will greatly improve the download speed for broadband users. It uses the servers in {{ic|/etc/pacman.d/mirrorlist}} as mirrors in aria2. What happens is that aria2 downloads from multiple servers simultaneously which gives a huge boost in download speed.
+
This script will greatly improve the download speed for broadband users. It uses the servers in {{ic|/etc/pacman.d/mirrorlist}} as mirrors in aria2. What happens is that aria2 downloads a single package from multiple servers simultaneously which gives a huge boost in download speed.
  
 
{{Note|You have to put 'exec' before /usr/bin/pacget in the XferCommand. This is needed so that when you terminate pacget or aria2 (with process id used by pacget), pacman would also terminate. This would prevent inconvenience because Pacman would not persist downloading a file when you tell it not to.}}
 
{{Note|You have to put 'exec' before /usr/bin/pacget in the XferCommand. This is needed so that when you terminate pacget or aria2 (with process id used by pacget), pacman would also terminate. This would prevent inconvenience because Pacman would not persist downloading a file when you tell it not to.}}

Revision as of 20:48, 9 December 2012

Improving Database Access Speeds

Pacman stores all package information in a collection of small files, one for each package. Improving database access speeds reduces the time taken in database-related tasks, e.g. searching packages and resolving package dependencies. The safest and easiest method is to run as root:

# pacman-optimize

This will attempt to put all the small files together in one (physical) location on the hard disk so that the hard disk head does not have to move so much when accessing all the packages. This method is safe, but is not foolproof. It depends on your filesystem, disk usage and empty space fragmentation. Another more aggressive option would be to first remove uninstalled packages from cache and to remove unused repositories before database optimization:

# pacman -Sc && pacman-optimize

Improving Download Speeds

Note: If your download speeds have been reduced to a crawl, ensure you are using one of the many mirrors and not ftp.archlinux.org, which is throttled since March 2007.

Pacman's speed in downloading packages can be improved by using a different application to download packages instead of Pacman's built-in file downloader.

In all cases, make sure you have the latest Pacman before doing any modifications.

# pacman -Syu

Using Powerpill

Powerpill is a full wrapper for Pacman that uses parallel and segmented downloads to speed up the download process. Normally Pacman will download one package at a time, waiting for it to complete before beginning the next download. Powerpill takes a different approach: it tries to download as many packages as possible at once.

The Powerpill wiki page provides basic configuration and usage examples along with package and upstream links.

Using wget

This is also very handy if you need more powerful proxy settings than pacman's built-in capabilities.

To use wget, first install it with pacman -S wget and then modify /etc/pacman.conf by adding the following line to the [options] section:

XferCommand = /usr/bin/wget -c --passive-ftp -c %u

Instead of putting wget parameters in /etc/pacman.conf, you can also modify the wget configuration file directly (the system-wide file is /etc/wgetrc, per user files are $HOME/.wgetrc.

Using aria2

aria2 is a lightweight download utility with support for resumable and segmented HTTP/HTTPS and FTP downloads. aria2 allows for multiple and simultaneous HTTP/HTTPS and FTP connections to an Arch mirror, which should result in an increase in download speeds for both file and package retrieval.

Note: Using aria2c in Pacman's XferCommand will not result in parallel downloads of multiple packages. Pacman invokes the XferCommand with a single package at a time and waits for it to complete before invoking the next. To download multiple packages in parallel, see the powerpill section above.

Installation

Download and install aria2 and its dependencies:

# pacman -S aria2

Configuration

Edit /etc/pacman.conf by adding the following line to the [options] section:

XferCommand = /usr/bin/aria2c --allow-overwrite=true -c --file-allocation=none --log-level=error -m2 --max-connection-per-server=2 --max-file-not-found=5 --min-split-size=5M --no-conf --remote-time=true --summary-interval=60 -t5 -d / -o %o %u

Option Details

/usr/bin/aria2c
The full PATH to the aria2 executable.
--allow-overwrite=true
Restart download if a corresponding control file does not exist. (Default: false)
-c, --continue
Continue downloading a partially downloaded file if a corresponding control file exists.
--file-allocation=none
Do not pre-allocate file space before download begins. (Default: prealloc) 1
--log-level=error
Set log level to output errors only. (Default: debug)
-m2, --max-tries=2
Make 2 maximum attempts to download specified file(s) per mirror. (Default: 5)
--max-connection-per-server=2
Set a maximum of 2 connections to each mirror per file. (Default: 1)
--max-file-not-found=5
Force download to fail if a single byte is not received within 5 attempts. (Default: 0)
--min-split-size=5M
Only split the file if the size is larger than 2;5MB = 10MB. (Default: 20M)
--no-conf
Disable loading an aria2.conf file if it exists. (Default: ~/.aria2/aria2.conf)
--remote-time=true
Apply timestamps of the remote file(s) and apply them to the local file(s). (Default: false)
--summary-interval=60
Output download progress summary every 60 seconds. (Default: 60) 2
-t5, --timeout=5
Set a 5 second timeout per mirror after a connection is established. (Default: 60)
-d, --dir
The directory to store the downloaded file(s) as specified by pacman.
-o, --output
The output file name(s) of the downloaded file(s).
%o
Variable which represents the local filename(s) as specified by pacman.
%u
Variable which represents the download URL as specified by pacman.

Additional Notes

1 --file-allocation=falloc
Recommended for newer file systems such as ext4 (with extents support), btrfs or xfs as it allocates large files (GB) almost instantly. Do not use falloc with legacy file systems such as ext3 as prealloc consumes approximately the same amount of time as standard allocation would while locking the aria2 process from proceeding to download.
2 --summary-interval=0
Supresses download progress summary output and may improve overall performance. Logs will continue to be output according to the value specified in the log-level option.
3 XferCommand = /usr/bin/printf 'Downloading ' && echo %u | awk -F/ '{printf $NF}' && printf '...' && /usr/bin/aria2c -q --allow-overwrite=true -c --file-allocation=none --log-level=error -m2 --max-connection-per-server=2 --max-file-not-found=5 --min-split-size=5M --no-conf --remote-time=true --summary-interval=0 -t5 -d / -o %o %u && echo ' Complete!'
Using this XferCommand gives less useful, but much more readable, output.

Using powerpill-light

pacman2aria2 provides a script named "powerpill-light", which was a stopgap created after the deprecation of the original powerpill written in Perl. Now that Powerpill has been re-released, powerpill-light is deprecated.

pacget (aria2) Mirror Script

This script will greatly improve the download speed for broadband users. It uses the servers in /etc/pacman.d/mirrorlist as mirrors in aria2. What happens is that aria2 downloads a single package from multiple servers simultaneously which gives a huge boost in download speed.

Note: You have to put 'exec' before /usr/bin/pacget in the XferCommand. This is needed so that when you terminate pacget or aria2 (with process id used by pacget), pacman would also terminate. This would prevent inconvenience because Pacman would not persist downloading a file when you tell it not to.
Warning: You may experience some problems if the mirrors used are out-of-sync or are simply not up-to-date. Just use the Reflector script to generate a list of up-to-date and fast mirrors. Also, ftp.archlinux.org resolves to two IPs. You may want to choose only one of them and hard code ftp.archlinux.org and the chosen IP address to /etc/hosts.
/usr/bin/pacget
#!/bin/bash

msg() {
  echo ""
  echo -e "   \033[1;34m->\033[1;0m \033[1;1m${1}\033[1;0m" >&2
}

error() {
  echo -e "\033[1;31m==> ERROR:\033[1;0m \033[1;1m$1\033[1;0m" >&2
}

CONF=/etc/pacget.conf
STATS=/etc/pacget.stats
ARIA2=$(which aria2c 2> /dev/null)

# ----- do some checks first -----
if [ ! -x "$ARIA2" ]; then
  error "aria2c was not found or isn't executable."
  exit 1
fi

if [ $# -ne 2 ]; then
  error "Incorrect number of arguments"
  exit 1
fi

filename=$(basename $1)
server=${1%/$filename}
arch=$(grep ^Architecture /etc/pacman.conf | cut -d '=' -f2 | sed 's/ //g')
if [[ $arch = "auto" ]]; then
  arch=$(uname -m)
fi
# Determine which repo is being used
repo=$(awk -F'/' '$(NF-2)~/^(community|core|extra|testing|comunity-testing|multilib)$/{print $(NF-2)}' <<< $server)
[ -z $repo ] && repo="custom"

# For db files, or when using a custom repo (which most likely doesn't have any mirror),
# use only the URL passed by pacman; Otherwise, extract the list of servers (from the include file of the repo) to download from
url=$1
if ! [[ $filename = *.db || $repo = "custom" ]]; then
  mirrorlist=$(awk -F' *= *' '$0~"^\\["r"\\]",/Include *= */{l=$2} END{print l}' r=$repo /etc/pacman.conf)
  if [ -n mirrorlist ]; then
    num_conn=$(grep ^split $CONF | cut -d'=' -f2)
    url=$(sed -r '/^Server *= */!d; s/Server *= *//; s/\$repo'"/$repo/"'; s/\$arch'"/$arch/; s/$/\/$filename/" $mirrorlist | head -n $(($num_conn *2)) )
  fi
fi

msg "Downloading $filename"
cd /var/cache/pacman/pkg/

touch $STATS

$ARIA2 --conf-path=$CONF --max-tries=1 --max-file-not-found=5 \
  --uri-selector=adaptive --server-stat-if=$STATS --server-stat-of=$STATS \
  --allow-overwrite=true --remote-time=true --log-level=error --summary-interval=0 \
  $url --out=${filename}.pacget && [ ! -f ${filename}.pacget.aria2 ] && mv ${filename}.pacget $2 && chmod 644 $2

exit $?
/etc/pacget.conf
# The log file
log=/var/log/pacget.log
# Number of servers to download from
split=5
# Minimum file size that justifies a split, i.e. concurrent download (default 20M)
min-split-size=1M
# Maximum download speed (0 = unrestricted)
max-download-limit=0
# Minimum download speed (0 = do not care)
lowest-speed-limit=0
# Server timeout period
timeout=5
# 'none' or 'falloc'
file-allocation=none

Save this script as /usr/bin/pacget.

# chmod 755 /usr/bin/pacget

This makes the script an executable

In /etc/pacman.conf, in the [options] section, the following needs to be added:

XferCommand = exec /usr/bin/pacget %u %o
Note: If you use ftp.archlinux.org as the first server listed in your include files (/etc/pacman.d/*), some problems may occur when the mirrors you are using have not yet synced. To make great use of this script, choose a mirror (that syncs in a timely manner) that is more appropriate for you, then put that on top of the server lists. This is to prevent downloading only from ftp.archlinux.org when the mirrors have not yet synced. The rankmirrors script can be useful in this case.

Using other applications

There are other downloading applications that you can use with Pacman. Here they are, and their associated XferCommand settings:

  • snarf: XferCommand = /usr/bin/snarf -N %u
  • lftp: XferCommand = /usr/bin/lftp -c pget %u
  • axel: XferCommand = /usr/bin/axel -n 2 -v -a -o %o %u

Choosing the fastest mirror

When downloading packages pacman uses the mirrors in the order they are in /etc/pacman.d/mirrorlist.The mirror which is at the top of the list by default however may not be the fastest for you.

Note: This does not apply to powerpill-light, which connects to many servers simultaneously to increase the overall download speed. The speed of individual connections becomes less relevant, and powerpill-light can be configured to require minimum speeds per connection.

Choosing a local mirror

The simple way is to edit mirrorlist file by placing a local mirror at the top of the list. pacman will then use this mirror for preference.

Alternativley the pacman.conf file can be edited by placing a local mirror before the line sourcing the mirrorlist file, i.e. where it says "add your preferred servers here". It is safer if you use the same server for each repository.

Using rankmirrors

You can use rankmirrors to rank pacman mirrors by their connection and opening speed.

Using Reflector

You can also use Reflector to retrieve a customized list of mirrors sorted by download speed.

After changing mirrors

After changing your mirror it is a good idea to refresh the pacman database. Using two y's forces a download of a fresh copy of the master package list from the server even if they are thought to be up to date.

# pacman -Syy

Sharing packages over your LAN

If you happen to run several Arch boxes on your LAN, you can share packages so that you can greatly decrease your download times. Keep in mind you should not share between different architectures (i.e. i686 and x86_64) or you'll get into troubles.

See Pacman_Tips#Network_shared_pacman_cache.