Subject: Re: Proposed new syscalls: pread and pwrite
To: None <>
From: Stefan Grefen <>
List: tech-kern
Date: 12/05/1995 05:41:41
In message <>  "J.T. Conklin" wrote:
> My officemate Stu was reading the Solaris manual last Friday and
> noticed the syscalls pread() and pwrite().  Those calls are like
> read() and write() but also take an offset argument like lseek().
> He mentioned that TOPS-20 had something similar, and it resulted 
> in a 10-15% performance improvement on database like applications.

What you see is the systemcall overhead for the lseek. Make syscalls
faster and the benefit becomes smaller and smaller ...


> Although the type of applications that benefit from this new syscall
> is small, I think the performance improvement warrants the inclusion
> of these new syscalls in NetBSD.  Even such things as mundane as DB
> would seem to benefit from the new functionality.

Every program would benefit from faster syscalls ...

I'm working for a company building 'scalable' system. Most time the 
scalabilty is limited by poorly designed/implemented basic functions.
That's why I'm stressing the 'basics' here.
(For SLOWARIS compatibility the syscall is of course needed and on a
 multi-cpu system it's mandatory or atomic seek/writes become a very
 complicated and slow function).



> 	--jtc

Stefan Grefen                          Convex Computer GmbH, Frankfurt, Germany		       Phone: +49-69-665270
fortune: "You can't make a program without broken egos."