Date   : Fri, 07 Jun 1996 11:53:26 +0100
From   : angus@...
Subject: DFS buffer sizes?

Mark de Weger writes:
>  How large are the read and write buffers the BBC DFSs (DFS1.2
>  would be all right; I don't guess there's a lot of difference
>  between the different DFSs) set aside for bget/bput file 
>  operations.

256 bytes. Don't use bget/bput. They have *far* too much overhead associated
with them. Use OSGBPB, then you'll only have the overhead once, for whatever
buffer size you want to use.

Data from my benchmarking tests when writing HDFS:

Times are in seconds. Out indicates file opened for output only, Up indicates
opened for update. Fast indicates using second processor fast bput call. IO
indicates IO processor, Tube indicates second 6502 processor. All tests
include disc spin-up time:

		HDFS	HDFS	HDFS	DNFS
BPUT 32K	Root	Subdir	Acorn	1.20
Out            	54.32	54.36	54.33	55.02
Up             	76.04	75.75	76.28	76.03
Fast, Out      	28.80	29.23	28.42	29.41
Fast, Update   	49.92	49.75	50.46	50.0


		HDFS	HDFS	HDFS	DNFS
BGET 32K	Root	Subdir	Acorn	1.20
Get            	52.70	52.50	52.71	52.8

 
		HDFS	HDFS	HDFS	DNFS
GBPB		Root	Subdir	Acorn	1.20
Read, IO       	29.11	29.17	29.12	29.24
Read, Tube     	29.14	29.17	29.11	29.24
Write, IO      	29.28	29.40	29.28	29.27
Write, Tube    	29.27	29.39	29.27	29.2

The columns are:
	HDFS Root	HDFS format disc, operating in root directory
	HDFS Subdir	HDFS format disc, operating in sub-directory
	HDFS Acorn	HDFS operating on DFS format disc
	DNFS 1.20	Acorn DNFS 1.20 operating on DFS format disc

(HDFS format is *very* similar to DFS format.)

a.
--
Angus Duggan, Harlequin Ltd., Barrington Hall,	| INET: angus@...            
Barrington, Cambridge CB2 5RG, U.K.		| FAX: +44(0)1223 873873