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From: evans@ditsyda.oz (Bruce Evans)
Newsgroups: comp.os.minix
Subject: Re: Disk performance under Minix
Message-ID: <2141@ditsyda.oz>
Date: 24 Aug 89 17:00:26 GMT
References: <21978@louie.udel.EDU>
Reply-To: evans@ditsyda.mq.oz (Bruce Evans)
Organization: CSIRO DIT Sydney, Australia
Lines: 42

In article <21978@louie.udel.EDU> HELMER%SDNET.BITNET@vm1.nodak.edu (Guy Helmer) writes:
>I removed the WRITE_IMMED's from buf.h and then re-tried my tests.  For
>the 256 1k block fopen/fwrite test, timings improved from
>...
>               fwrite                 write
>Test      Real  User  Sys        Real  User  Sys
>...
>  2       10.0   5.4  0.4         5.0   0.0  0.5	[slowest of 5]
>...

Some more reference points for fwriting 256K on Minix
(open, fwrite, close; sync; for 386, do 10 times and divide later by 10):

cpu		disk		O/S	stdio	cache	real	user	sys

8088/4.77	3:1/80ms	1.3	1.3	 30K	117.0	66.7	 7.2
8088/4.77	3:1/80ms	1.4b-	1.3	 30K#	 81.0	58.5	 9.5
8088/4.77	3:1/80ms	1.3	mine	 30K	 56.0	 0.5	 4.9
8088/4.77	3:1/80ms	1.3+	mine	 30K	 43.0	 0.3	 5.1
8088/4.77	3:1/80ms	1.4b-	mine	 30K#	 22.0	 0.2	10.8
386/20/16 bits	2:1/28ms	1.4b-	mine	 30K#	  6.6	  .02	  .79
386/20/16 bits	2:1/28ms	1.4b-	mine	 50K#	  6.2	  .02	  .77
386/20/32 bits	2:1/28ms	1.4b-	mine	 30K#	  3.2	  .02	  .59
386/20/32 bits	2:1/28ms	1.4b-	mine	 50K#	  2.7	  .02	  .59
386/20/32 bits	2:1/28ms	1.4b-	mine	320K#	  2.3	  .02	  .63

1.3+ is my old version of 1.3 (bests parts are in 286 posting).
'#' means my modified cache and drivers. The driver got NR_BUFS - 5 blocks
in most requests in these tests.

The 16-bit 386 times are consistent with Guy's times for write. A little
slower. The grouped writes are *not* helping. Yet they do help with 32-bits
and the same cache size, and read times are identical in 16 and 32-bit modes!
The reason is that there is little time to spare in keeping up with the
interleave (50 micrsosec for write and 150 microsec for read), and 16-bit
mode is a little slower (mainly from 32-bit divisions in 16-bit software).
This highlights the problem of keeping up on slower machines. 3:1 interleave
should be OK for AT's with only a little work on the driver.

I'll be happy with times of 4 sec for the 8088 and 1.5 sec for the 386.
-- 
Bruce Evans		evans@ditsyda.oz.au