Re: A question about slum and relocate

[Alex Zarochentsev <zam@namesys.com>]

On Tue, Nov 25, 2003 at 01:19:03PM +0300, Alex Zarochentcev wrote:
> On Mon, Nov 24, 2003 at 06:50:07PM -0500, Zhihui Zhang wrote:
> > Hi,
> > 
> > After reading some code, it seems to me that a slum does not have to be
> > relocated.  If a slum is small , it will use the overwrite strategy.  Is
> > this understanding correct?  
> 
> Not exactly.
> 
> If slum is big we set pos->leaf_relocate and always relocate leaf nodes.
> Except this, flush alg. makes relocate/overwrite decision individually for each
> node. Leaves can be relocated even if slum size < FLUSH_RELOCATE_THRESHOLD.
> 
> > Also, at the leaf level, if the number of
> > dirty nodes exceeds FLUSH_RELOCATE_THRESHOLD (64), they are always
> > relocated.  Is there any similar threshold for an internal level?  
> 
> no.
> 
> > Does Reiser4 relocate internal nodes separately (i.e. not as part of the slum
> > involving leaf nodes.  
> 
> yes.

Seems I did not understand your question correctly.

The flush position state has a "preceder" object.  It is used as a search start
when reiser4 relocates node and it is set to node's block number after
finishing node processing.  But the relocate/overwrite decision is made
individually for each node.  If there is enough free space all nodes will be
allocated close one to each other.

-- 
Alex.