Bug 527502 - collector should not sort the generated lists
Summary: collector should not sort the generated lists
Alias: None
Product: Fedora
Classification: Fedora
Component: readahead
Version: 12
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Harald Hoyer
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2009-10-06 17:00 UTC by Raphael Geissert
Modified: 2010-12-04 07:33 UTC (History)
1 user (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2010-12-04 07:33:07 UTC
Type: ---

Attachments (Terms of Use)
Preserve he order in which the files are used when writting the files lists (1.70 KB, patch)
2009-10-06 17:00 UTC, Raphael Geissert
no flags Details | Diff

Description Raphael Geissert 2009-10-06 17:00:40 UTC
Created attachment 363857 [details]
Preserve he order in which the files are used when writting the files lists

In the case of SSDs, it is not of much use to sort the files lists by block order. It is more important to readahead the files in the order they will be needed by the programs, so that readahead can be backgrounded.

As a first step, it is necessary to preserve the order in which the files are accessed. The attached (or to be attached, depending on whether bugzilla likes it or not) patch does exactly that.

Comment 1 Harald Hoyer 2009-10-06 17:04:48 UTC
Hmm, does it make sense for SSDs anyway?
Sorting is mainly because of seek time, which is the main gain from readahead.
For SSDs starting initscripts in parallel would make the most sense (like upstart does in newest Ubuntu).

Comment 2 Raphael Geissert 2009-10-07 00:53:24 UTC
Starting init scripts in parallel is helpful in all cases, on Debian we now use a dependencies-based rc which allows us to start scripts in "makefile" mode, i.e. as soon as their dependencies are satisfied. The boot time is reduced in all cases.
In the case of SSDs, using readahead as a backgrounded, low priority, preloading mechanism of the files still reduces the boot time. The trick in the case of SSDs is to preload in the order in which the files will be used. Ideally readahead will have preloaded the files needed by an application before the application requests it to the kernel.
In the case of HDDs the best performance is achieved by preloading by the blocks order[1] with a normal io priority, in the foreground, without having any other application that may request disk access running at the same time.

[1] I do have plans to make readahead work this way, but some major code structure changes are needed. Hope I can count on you to make that happen.

Comment 3 Bug Zapper 2009-11-16 13:19:12 UTC
This bug appears to have been reported against 'rawhide' during the Fedora 12 development cycle.
Changing version to '12'.

More information and reason for this action is here:

Comment 4 Bug Zapper 2010-11-04 09:37:21 UTC
This message is a reminder that Fedora 12 is nearing its end of life.
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Comment 5 Bug Zapper 2010-12-04 07:33:07 UTC
Fedora 12 changed to end-of-life (EOL) status on 2010-12-02. Fedora 12 is 
no longer maintained, which means that it will not receive any further 
security or bug fix updates. As a result we are closing this bug.

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