Asynch socket IO

Asynch socket IO

Post by Thomas Paul Anders » Tue, 23 Aug 1994 05:11:47

I am trying to port an application to Linux and am having trouble when
I go to set the process group ( i.e. ioctl( sd, SIOCSPGRP, -getpid() )
to receive a SIGIO/SIGPOLL when there is data on the socket.  The above
call always seems to return with -1 and a "invalid parameter" errno.

Since this is the last in a string of calls ( getsockopt, setsockopt, ioctl,
etc.) that manipulate the socket I feel confident that the descriptor is
valid, so what is the "invalid parameter"??

I have also tried to use "fcntl(sd, F_SETOWN, getpid())" with the same



1. Asynch IO and Oracle


I was wondering what a good value for asynchronous IO on AIX
would be. The default was 1 min 10 max (number of servers). I
read somewhere that on a 4 disk system values of 10 min 40 max
was recommended.

I have a 6 CPU S80 server with 8 GB of RAM and 8 drawers of
SSA disks (128 disks of 9 GB). I am running 16 Oracle databases
on it. Most are small but I have 4 large databases with 50
datafiles each. Each of the 4 large databases has 4 database
writer processes (dbw0 dbw1 dbw2 dbw3).

I set min to 100 and max to 1000 in 'smit aio'. 4*4*50 also
implies a value of that size. If I use 'ps -Af|grep kproc'
there are 1017 processes, so all AIO processes are started
and being used. However I am not seeing much performance
improvement from back when the maximum was set to 100.

Except that occasionally the system seemed to freeze, with
uptime and ps showing almost nothing running, while users were
complaining about slow queries. I contributed that to lack of
AIO processes and upped it to 1000.

What is a good value for those AIO parameters ? Or is 1000
excessive and hurting performance ? Should I use 4 database
writers for each database on a 6 CPU system with asynch IO,
or just one ?


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