Re: Ext2 Directory Index - Delete Performance

[Rik van Riel]

On Thu, 19 Apr 2001, Daniel Phillips wrote:
> Jan Harkes wrote:
> > On Thu, Apr 19, 2001 at 02:27:48AM +0200, Daniel Phillips wrote:
> > > more memory.  If you have enough memory, the inode cache won't thrash,
> > > and even when it does, it does so gracefully - performance falls off
> > > nice and slowly.  For example, 250 Meg of inode cache will handle 2
> > > million inodes with no thrashing at all.
> > 
> > What inode cache are you talking about? According to the slabinfo output
> > on my machine every inode takes up 480 bytes in the inode_cache slab. So
> > 250MB is only able to hold about half a million inodes in memory.           
>                                                                  
> Sorry, I was a little loose with terminology there.  I should have
> said "inode blocks in cache".  The inode cache is related.  When an
> Ext2 inode is pushed out of the inode cache it gets transfered to a
> dirty block in memory, where it shrinks to 128 bytes and shares the
> block with 31 other inodes.  These blocks are in the buffer cache, and
> this is the cache I'm talking about.

Hmmm, considering this, it may be wise to limit the amount of
inodes in the inode cache to, say, 10% of RAM ... because we
can cache MORE inodes if we store them in the buffer cache
instead!

regards,

Rik
--
Virtual memory is like a game you can't win;
However, without VM there's truly nothing to lose...

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