[dm-devel] Re: [PATCH 2 of 2] DM Snapshot: dont insert before existing chunk

[Mikulas Patocka]

On Thu, 24 Sep 2009, Alasdair G Kergon wrote:

> On Wed, Sep 23, 2009 at 10:25:08AM -0500, Jon Brassow wrote:
> > Don't insert into hash before an existing chunk.
> > Most inserts are after an existing extent anyway so this code is used
> > very rarely.
>  
> Again, I'm not particularly keen on taking this one.  Some systems are very
> short of memory and everything we can save matters and we have no statistics
> about how "rare" this actually is.
> 
> Is it really that difficult to split into two when removing?

It is code bloat --- it would increase coding/reviewing/testing time (the 
splitting would have to be simulated because it happens rarely).

Also, it could lead to the situation that memory consumption starts 
growing when merging.

Mikulas

> Alasdair
>