Re: Processes vs Threads
Date: 1 Nov 1994 22:06:11 -0600
Message-ID: <39737j$81_at_tamsun.tamu.edu>
In article <3962g6$8c0_at_news.inbe.net>, Nick Price <nick_at_falstaff> wrote:
>The Oracle architecture is highly process centric, in that a typical
>instance architecture utiises (at least on UNIX) seperate processes to
>accomplish discrete tasks.
>
>The lightweight process/thread execution model (ie Pthreads) where
>therads execute within the address space of the parent process would seem
>to offer scope for considerable parallelism. How if at all could this
>model be used for a DBMS system such as Oracle ?
>
>Nick
>--
The main advantage of multi-threading is the increased speed of computation
due to parallelism . This is because context switching required to execute a
different thread is considerably less than the context switching overhead to
execute a different process.(BTW A context switch is the process by which a
CPU which is running one process save the status of the process in its memory
loads another process from memory and starts running it.) This makes a lot
of sense where Oracle is used as a server in a client-server application.
Instead of forking new Oracle server processes to service clients now only
one Server process with multiple threads needs to be available. This saves
a lot of context switching time on the server thereby increasing throughput.
Consider this example : There are two Oracle clients requesting services from
a server. Instead of spawning two server process to service this two clients
we use one server with two threads to service these clients.
The thread model which u described is the threads in user space. Current
generation operating systems like Solaris provide kernel multi-threading
wherein the O/S takes control of threads. But User Space threads is the
way to go.
A big "thread" on this issue-multi-threading is/was going on comp.os.research.
Oracle is server multi-threaded. The SQLDBA menu has some parameters which can
be used to configure the Oracle multi-threaded server. RTFM should give u
some interesting Information on threads.
If u have futher questions e-mail me.
Thanks
Mahesh Vallampati
M.S. In EE
Dept.of Electrical Engineering,
Texas A & M University.
Ph:(409)862-1070
// The only standard thing about Unix system is the message of the day asking users to clean up their files. Received on Wed Nov 02 1994 - 05:06:11 CET