Arch Linux

ermin

Member

Registered: 2009-02-21

Posts: 9

[Solved] Pacman is slow (I don't mean the download speed)

Imagine staring at the following console output for 4 minutes:

# pacman -Su
:: Starting full system upgrade...

The worst is that it causes a lot of I/O, making the whole system noticablly slower.
Same thing when I try to install/remove/query a package.
Running it a second time is faster, so I guess something is cached there.
Pacman-optimize does not help.

What could be the problem here?

(It has nothing to do with download speed. At that point nothing is being downloaded.)

Last edited by ermin (2009-09-18 04:23:41)

bangkok_manouel

Member

From: indicates a starting point

Registered: 2005-02-07

Posts: 1,556

Re: [Solved] Pacman is slow (I don't mean the download speed)

what's your file system?

ermin

Member

Registered: 2009-02-21

Posts: 9

Re: [Solved] Pacman is slow (I don't mean the download speed)

Filesystem is ext3

toofishes

Developer

From: Chicago, IL

Registered: 2006-06-06

Posts: 602

Website

Re: [Solved] Pacman is slow (I don't mean the download speed)

The pacman database is a bunch of scattered files in /var/lib/pacman/, and if your disk is particularly slow and the files aren't laid out well, it can require a lot of random access to pull all of these files into filesystem cache. RAM helps a lot here; it also helps if you aren't maxing out your memory in use by programs and have plenty left for the cache and buffers.

V01D

Member

Registered: 2006-07-18

Posts: 128

Re: [Solved] Pacman is slow (I don't mean the download speed)

try deadline scheduler, that will probably help as far as system responsiveness goes

ermin

Member

Registered: 2009-02-21

Posts: 9

Re: [Solved] Pacman is slow (I don't mean the download speed)

Thanks.
The deadline I/O scheduler really helped. I didn't have time to test it extensively, but it seems like the whole system is more responsive.

Here and here are links with more information on I/O schedulers and how to switch them.

Edit: Bonus points to the one who can give a simple explanation as to why it helped.

Last edited by ermin (2009-09-18 04:27:10)

sand_man

Member

From: Australia

Registered: 2008-06-10

Posts: 2,164

Re: [Solved] Pacman is slow (I don't mean the download speed)

Wasn't there a pacman db optimiser of some sort floating around?

btw: I guess this is a good idea to have /var on a separate partition

Last edited by sand_man (2009-09-18 06:32:47)

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quarkup

Member

From: Portugal

Registered: 2008-09-07

Posts: 497

Website

Re: [Solved] Pacman is slow (I don't mean the download speed)

could /var be stored in RAM ** safely ** ?

should I do something like this ?
http://wiki.archlinux.org/index.php/Ramdisk

thanks

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If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is.
Simplicity is the ultimate sophistication.

sand_man

Member

From: Australia

Registered: 2008-06-10

Posts: 2,164

Re: [Solved] Pacman is slow (I don't mean the download speed)

could /var be stored in RAM ** safely ** ?

should I do something like this ?
http://wiki.archlinux.org/index.php/Ramdisk

thanks

Sure why not.

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quarkup

Member

From: Portugal

Registered: 2008-09-07

Posts: 497

Website

Re: [Solved] Pacman is slow (I don't mean the download speed)

k thanks

---

If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is.
Simplicity is the ultimate sophistication.

kgas

Member

From: Qatar

Registered: 2008-11-08

Posts: 718

Re: [Solved] Pacman is slow (I don't mean the download speed)

I read nooms method to improve the pacman speed. Also using some download accelerator (XferCommand) will improve the pacman speed. The filesystem as mentioned by bangkok_manouel plays a role. In my experience resierfs is very nice for /var partition.

ataraxia

Member

From: Pittsburgh

Registered: 2007-05-06

Posts: 1,553

Re: [Solved] Pacman is slow (I don't mean the download speed)

I'm also using the "pacman DB in a file" AKA "pacman-cage" method, except I'm using reiserfs on my loopback image rather than plain ext2. You wouldn't think that would work so well, but it really does.

ermin

Member

Registered: 2009-02-21

Posts: 9

Re: [Solved] Pacman is slow (I don't mean the download speed)

I read nooms method to improve the pacman speed. Also using some download accelerator (XferCommand) will improve the pacman speed. The filesystem as mentioned by bangkok_manouel plays a role. In my experience resierfs is very nice for /var partition.

There is a script to automate the whole process here. It should be a bit more secure than doing it yourself.