Subject: Re: slowdown with MI scsi on pmax (ds5000/200)
To: None <tech-kern@netbsd.org, port-pmax@netbsd.org>
From: Toru Nishimura <nisimura@itc.aist-nara.ac.jp>
List: tech-kern
Date: 05/21/2001 17:03:57
Chuck Silvers <chuq@chuq.com> wrote;

> hi,
>
> I went back to run some benchmarks on my decstation 5000/200 again
> first the first time in about a month, and I find that scsi performance
> has dropped considerably.

I'm experiencing similars on my DECstation.

My 1.5V kernel for 33MHz R3000A DECstation brings strange SCSI
performance figures I've never seen before.

  NetBSD 1.5V (MAXINE) #0: Tue May  8 13:28:54 JST 2001
      nisimura@build:/usr/src/sys/arch/pmax/compile/MAXINE

iozone consistently shows WRITE runs half than READ.

  IOZONE performance measurements:
        869285 bytes/second for writing the file
        2111935 bytes/second for reading the file

The READ performance is restored as good as the one when I made pmax
MI SCSI driver years ago, but WRITE is the worst as long as I know.
iostat and vmstat indicate the kernel beats SCSI hardware par with the
data rate.

$ /usr/sbin/iostat -D 1
   KB xfr time 
  ...
  854  15 0.52 
  743  16 0.46 
  760  18 0.55 
  786  15 0.48    <------ write has finished here
 1311  33 0.63    <------ starts reading
 2039  34 0.70 
 2091  34 0.70 
 1904  34 0.72 
  ...

$ vmstat 1
 procs   memory     page                       disk faults      cpu
 r b w   avm   fre  flt  re  pi   po   fr   sr s0   in   sy  cs us sy id
 ...
 1 0 0 20860  1192    0   0   0  215    0    0 15    0    0   0  1 99  0
 1 0 0 21708   344    0   0   0  213    0    0 16    0    0   0  0 98  2
 1 0 0 21436   616    0   0   0  213    0    0 14    0    0   0  1 99  0
 1 0 0 21048  1008    0   0   0  182    0    0 16    0    0   0  1 92  7 <- W
 1 0 0 21572   464    0   0   0  213    0    0 38    0    0   0  1 83 16 <- R
 1 1 0 21276   780    0   1   0  257    0    0 34    0    0   0  2 91  7
 1 0 0 20960  1036    0   2   0  258    0    0 33    0    0   0  3 90  8
 1 0 0 20704  1292    0  14   0  393    0    0 32    0    0   0  2 66 32
 1 0 0 20768  1232    0   1   0  280    0    0 33    0    0   0  2 92  6
 ...

The NetBSD/pmax kernel has, UBC, "UBC fix for throttling", SCSIPI
integration and kthread fix.

Tohru Nishimura