LiveCDPerformance

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== Status ==

  * Created: [[Date(2005-04-23T03:04:58Z)]] by MattZimmerman[[BR]]
  * Priority: MediumPriority[[BR]]
  * People: MatthewGarrettLead, FabioDiNittoSecond[[BR]]
  * Contributors: MattZimmerman[[BR]]
  * Interested: JuanjeOjeda[[BR]]
  * Status: BreezyGoal, DraftSpec[[BR]]
  * Branch: [[BR]]
  * Malone Bug: [[BR]]
  * Packages: [[BR]]
  * Depends: [[BR]]
  * UduSessions: 2 [[BR]]		  * '''Launchpad Entry''': https://launchpad.net/distros/ubuntu/+spec/live-cd-performance
 * '''Created''': <<Date(2005-04-23T03:04:58Z)>> by MattZimmerman<<BR>>
 * '''Contributors''': TollefFogHeen, MattZimmerman
 * '''Packages affected''': casper
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== Scope and Use Cases ==
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Performance issues in two areas:  1. Instrumentation is required in order to identify bottlenecks. d-i logs stage 1, we can wrap init scripts to provide timing information on their startup. Bootchart would also be useful. Bootchart wraps init and would be used for instrumenting stage 2. It stores it information in the live cd system where it could be uploaded to a central location such as bugzilla.
 2. Enable DMA on livecd - it may not work on some systems, but it's effectively required
 3. Readahead may be a performance win with 256MB or more, but slower otherwise. Verify with different memory configurations, and ensure that readahead is only enabled when it's a performance benefit. http://unit.aist.go.jp/itri/knoppix/readahead/index-en.html has figures for Knoppix on cloop.
 4. Filesystem comparison - squashfs and unionfs may give a performance benefit. http://listas.hispalinux.es/pipermail/metadistros-dev/2005-April/000580.html suggests a 50 second improvement.
 5. Background network setup - this can be left for when the user has hit the desktop (NetworkMagic)
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1) Installer

 * Can generation of locales be made faster?

Generic CD required - we need to be able to ship them to the rest of the world.

 * Background things like network setup?

We don't actually need setup the network at the beginning

(trivial: get Colin to do it)

2) Post-di boot

 * Readahead configuration may be suboptimal
Seems not very helpful. See this experiment on Knoppix (the same compress filesystem: cloop):
http://unit.aist.go.jp/itri/knoppix/readahead/index-en.html

If we have more than 256Mb we enable readhead otherwise no. Needs implementation.
(high priority).

 * The dma activations help, but no so much.
(requires more investigation)

 * We need check out the filesystem compression (whichever we want to use: cloop, squashfs, unionfs...) performance. But seems this is not the main problem.
(unionfs is in the kernel but not for ppc - i386 is go for basic testing)

 * Somebody did a comparative between the official Kubuntu live CD and the same content of the image but compress with ''Squashfs'' instead of ''cloop'' and ''unionfs'' instead of ''device-mapper''. Also he used the [http://metadistros.hispalinux.es Metadistros] live system. The result was the second one takes 50 sec less than Kubuntu to boot.
http://listas.hispalinux.es/pipermail/metadistros-dev/2005-April/000580.html
(High priority: work in progress - unionfs is in the kernel - needs testing)

NEEDS INSTRUMENTATION - do we have detailed enough logfiles?

Use invoke-rc.d to timestamp runlevels, we have timestamped printk in the kernel
and d-i produces logs with enough details.

IMPLEMENTATION:

 1. Full timings for initial install and second-stage boot.
 2. For packages that spend an extended amount of time in configure, see if that can be improved
 3. Test different filesystems
 4. Investigate the interaction of readahead with the current compressed filesystem - are we spending more time seeking than we'd spend just loading the programs anyway?
 5. Speed up any d-i modules (locale generation?) that consume large amounts of time
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none. None.
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could be several. For instrumentation, init requires modification or bootchart, which will be a better choice. Performance issues in the first stage install will require d-i modifications. Any slow packages in second stage boot will need tweaks to improve performance.
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none. None.
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== Outstanding Issues ==

unionfs on ppc.

=== UDU BOF Agenda ===

 * d-i performance
 * casper performance
 * Ubuntu boot performance (FasterBoot)

=== UDU Pre-Work ===

 * Profile the live CD boot sequence to measure the time taken for each step
  * d-i startup (time-to-first-question)
  * Pre-casper d-i activity (measured per menu entry)
  * Casper d-i activity (measured per casper.d script)
  * Standard boot sequence		 ----
CategorySpec

Live CD Performance

Introduction

The boot time for the Ubuntu live CD should be comparable (or superior) to other popular live CDs.

Rationale

The better the load time, the better the live CD experience, the greater chance an end user will want to use it and move on to installing Ubuntu or another distro.

Implementation Plan

  1. Instrumentation is required in order to identify bottlenecks. d-i logs stage 1, we can wrap init scripts to provide timing information on their startup. Bootchart would also be useful. Bootchart wraps init and would be used for instrumenting stage 2. It stores it information in the live cd system where it could be uploaded to a central location such as bugzilla.
  2. Enable DMA on livecd - it may not work on some systems, but it's effectively required

  3. Readahead may be a performance win with 256MB or more, but slower otherwise. Verify with different memory configurations, and ensure that readahead is only enabled when it's a performance benefit. http://unit.aist.go.jp/itri/knoppix/readahead/index-en.html has figures for Knoppix on cloop.

  4. Filesystem comparison - squashfs and unionfs may give a performance benefit. http://listas.hispalinux.es/pipermail/metadistros-dev/2005-April/000580.html suggests a 50 second improvement.

  5. Background network setup - this can be left for when the user has hit the desktop (NetworkMagic)

Data Preservation and Migration

None.

Packages Affected

For instrumentation, init requires modification or bootchart, which will be a better choice. Performance issues in the first stage install will require d-i modifications. Any slow packages in second stage boot will need tweaks to improve performance.

User Interface Requirements

None.

CategorySpec

LiveCDPerformance (last edited 2008-08-06 16:14:57 by localhost)