Fix for 4.0.1 / 8M RAM slow disk writes

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2 total messages Started by R. Lamberts Thu, 24 Dec 1992 01:34

#28

Author: R. Lamberts
Date: Thu, 24 Dec 1992 01:34

32 lines
1461 bytes

OK guys, don't laugh. I still have 8 meg and IRIX 4.0.1,
and was getting sick of the slow disk write bug. If you
are in the same situation (8 meg / 4.0.1), this crazy
fix may be of interest to you.

It appears that doing a file system sync 20 times a second
increases disk write speed enormously, without giving too
much overhead. So compile something like this:

main()
{
  do
  {
    sync();
    sginap(5);
  }
  while (1);
}

(Please don't whine about this not being the best example
of software engineering. ;-)

If you use applications that write to disk at very high
rates, you may try to decrease the sginap argument, but
that results in a noticeable system load. Most tools
run at maximum write speed with the code shown above.

Run this thingy in the background and you'll actually start
enjoying large cp or file un-tar actions...

- Reinoud

Re: Fix for 4.0.1 / 8M RAM slow disk writes

#29

Author: Dave Olson
Date: Sat, 26 Dec 1992 02:44

48 lines
2329 bytes

In <1992Dec24.013446.26848@donau.et.tudelft.nl> reinoud@dutecai.et.tudelft.nl (R. Lamberts) writes:


| OK guys, don't laugh. I still have 8 meg and IRIX 4.0.1,
| and was getting sick of the slow disk write bug. If you
| are in the same situation (8 meg / 4.0.1), this crazy
| fix may be of interest to you.
| 
| It appears that doing a file system sync 20 times a second
| increases disk write speed enormously, without giving too
| much overhead. So compile something like this:
| 
| main()
| {
|   do
|   {
|     sync();
|     sginap(5);
|   }
|   while (1);
| }
| 
| (Please don't whine about this not being the best example
| of software engineering. ;-)
| 
| If you use applications that write to disk at very high
| rates, you may try to decrease the sginap argument, but
| that results in a noticeable system load. Most tools
| run at maximum write speed with the code shown above.
| 
| Run this thingy in the background and you'll actually start
| enjoying large cp or file un-tar actions...

The best fix is to get 4.0.5.  This bug was introduced in the last days
of 4.0.1, and fixed in 4.0.2 (after I found it (I wasn't the one who
introduced this one!) and all later releases.  The code has changed
enough since then that I don't want to invest the time to see  just
what else might help; certainly dropping BDFLUSHR to 1 would have
similar effects, without using up another process slot and causing
more context switches.  I seem to recall that increasing NBUF would help
prevent the situation from arising, but I may be remembering wrong.

Doing it ever 50 msecs (as your program does) seems just a *bit*
excessive though!
--
Let no one tell me that silence gives consent,  |   Dave Olson
because whoever is silent dissents.             |   Silicon Graphics, Inc.
    Maria Isabel Barreno                        |   olson@sgi.com

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