[Cluster-devel] [GFS2 PATCH] GFS2: Block reservation doubling scheme

[Bob Peterson <rpeterso@redhat.com>]

----- Original Message -----
> ----- Original Message -----
> > This patch introduces a new block reservation doubling scheme. If we
> 
> Maybe I sent this patch out prematurely. Instead of doubling the
> reservation, maybe I should experiment with making it grow additively.
> IOW, Instead of 32-64-128-256-512, I should use:
> 32-64-96-128-160-192-224-etc...
> I know other file systems using doubling schemes, but I'm concerned
> about it being too aggressive.

I tried an additive reservations algorithm. I basically changed the
previous patch from doubling the reservation to adding 32 blocks.
In other words, I replaced:

+				ip->i_rsrv_minblks <<= 1;
with this:
+				ip->i_rsrv_minblks += RGRP_RSRV_MINBLKS;

The results were not as good, but still very impressive, and maybe
acceptable:

Reservation doubling scheme:
EXTENT COUNT FOR OUTPUT FILES =  310103
EXTENT COUNT FOR OUTPUT FILES =  343990
EXTENT COUNT FOR OUTPUT FILES =  332818
EXTENT COUNT FOR OUTPUT FILES =  336852
EXTENT COUNT FOR OUTPUT FILES =  334820

Reservation additive scheme (32 blocks):
EXTENT COUNT FOR OUTPUT FILES =  322406
EXTENT COUNT FOR OUTPUT FILES =  341665
EXTENT COUNT FOR OUTPUT FILES =  341769
EXTENT COUNT FOR OUTPUT FILES =  348676
EXTENT COUNT FOR OUTPUT FILES =  348079

So I'm looking for opinions:
(a) Stick with the original reservation doubling patch, or
(b) Go with the additive version.
(c) Any other ideas?

Regards,

Bob Peterson
Red Hat File Systems