LinuxQuestions.org
Did you know LQ has a Linux Hardware Compatibility List?
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Software > Linux - Kernel
User Name
Password
Linux - Kernel This forum is for all discussion relating to the Linux kernel.

Notices



Reply
 
Search this Thread
Old 02-03-2008, 03:51 AM   #1
PankajDS
Member
 
Registered: Oct 2007
Posts: 38

Rep: Reputation: 15
How delayed allocation is done in xfs, ext4fs ?


Hi all,
How delayed allocation is done in xfs, ext4fs ?
Thank you...........
 
Old 02-08-2008, 08:36 AM   #2
unSpawn
Moderator
 
Registered: May 2001
Posts: 27,713
Blog Entries: 54

Rep: Reputation: 2967Reputation: 2967Reputation: 2967Reputation: 2967Reputation: 2967Reputation: 2967Reputation: 2967Reputation: 2967Reputation: 2967Reputation: 2967Reputation: 2967
From the ext2 docs (which should apply to ext3 and 4 as well as far as I've read Cao's and Tso's work):
Quote:
Basically delayed allocation defers allocation of blocks from prepare_write() and employs extent walking, together with the multiple block allocation feature (described in the next section), for clustering block allocations maximally into contiguous blocks. Instead of allocating the disk block in prepare_write(), the the page is marked as needing block reservation. The commit_write() function calculates the required number of blocks, and reserves them to make sure that there are enough free blocks in the filesystem to satisfy the write. When the pages get flushed to disk by writepage() or writepages(), these functions will walk all the dirty pages in the specified inode, cluster the logically contiguous ones, and submit the page or pages to the bio layer. After the block allocation is complete, the reservation is dropped. A single block I/O request (or BIO) is submitted for write out of pages processed whenever a new allocated extent (or the next mapped extent if already allocated) on the disk is not adjacent to the previous one, or when writepages() completes.
If you mean how it is done code-wise then read the code ;-p
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Delayed Greetings! Tieren LinuxQuestions.org Member Intro 1 01-16-2006 10:31 AM
allocation jhon Programming 3 08-31-2004 09:52 AM
kdebase not recognizing XFree86-xfs package as xfs mikeyt_333 Linux - Software 1 08-17-2004 02:50 PM
Delayed ACK Z-Ice Linux - Networking 4 05-24-2004 04:46 PM
Pentium 4 delayed jeremy General 0 09-29-2000 01:54 PM


All times are GMT -5. The time now is 05:14 AM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration