Messages in this thread | | | Subject | Re: [PATCH] reiserfs v3 fixes and features | From | Chris Mason <> | Date | Tue, 06 Apr 2004 17:06:27 -0400 |
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On Tue, 2004-04-06 at 16:14, Marc-Christian Petersen wrote: > On Tuesday 06 April 2004 20:03, Chris Mason wrote: > > Hi Chris, > > > If anyone is interested in experimenting with the block allocator stuff, > > please let me know. > > I am :)
There are a few different sides to the block allocator work.
1) don't ruin what the current allocator is good at (desktop esp). A sequential tree read of freshly copied data is really fast right now. It could be a little better with some metadata readahead, I'm still trying to safely revive that code.
The patch tries to keep performance for a full tree read by with the -o packing_groups option. The basic idea is to reuse bitmap groups for new subdirectories until the bitmap group is full. This is done by checking to see how full a given part of the btree is.
2) Improve the fragmentation under multiple writers. With 20 writers, the default allocator breaks down, fragmenting badly (20% or so). The patch with -o alloc=skip_busy:dirid_groups on makes things sane (3%).
So, to help test, you need some way of measuring fragmentation and a whole bunch of benchmarks. I like fibmap: (http://www.informatik.uni-frankfurt.de/~loizides/reiserfs/fibmap.html)
But Andrew has a fragmentation tool in the ext2 cvs I think.
-chris
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