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From Dean Gaudet <dgau...@arctic.org>
Subject Re: [PATCH] make SVSEM default on Solaris
Date Tue, 04 Nov 1997 07:57:59 GMT


On Mon, 3 Nov 1997, Roy T. Fielding wrote:

> fielding@kiwi% time-SEM 160 1000
> accept_mutex_on: No space left on device
> accept_mutex_on: No space left on device
> accept_mutex_on: No space left on device
> accept_mutex_on: No space left on device
> WTF! shared_counter != num_child * num_iter!
>        3.268732

>From man semop:

     ENOSPC         The  limit  on  the  number   of   individual
                    processes  requesting  an  SEM_UNDO  would be
                    exceeded.

I wonder how you tune that limit.  I couldn't find anything obvious... 
it's probably one of those wonderfully documented /etc/system settings. 

FWIW, the limit seems to be 29 on one of the systems here.  This system
is an ultra 2 with dual 167MHz chips and 640Mb of RAM running 2.5.1.
Here's some timings:

% ./time-SEM 29 10000
       9.407788
% ./time-PTHREAD 29 10000
       1.309625
% ./time-PTHREAD 200 10000
       8.442355

I suspect there's a difference between UP and MP boxes just like there
is under IRIX, bleh.

Ok here's timings on a 2.5 system with 256Mb of RAM and a single 200Mhz
UltraSPARC:

% ./time-SEM 29 10000
       4.069612
% ./time-PTHREAD 29 10000
       1.687709
% ./time-PTHREAD 100 10000
       6.001535
% ./time-PTHREAD 200 10000
      11.638046

I dunno, I don't see the pthread problem you're seeing, that looks like
close to linear degredation for pthread.  Unlike, say, fcntl:

% =1/time-FCNTL 10 10000
       2.254160
% =1/time-FCNTL 30 10000
      17.364744
% =1/time-FCNTL 100 10000
      81.941647

Oh BTW Roy, if you're going to time fcntl then you should "cd /var/tmp"
or otherwise make sure your cwd is not NFS mounted ... 'cause that's
where the lock file will be created.  I just added a printf for that.

Dean


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