Suggestions on Avoiding syscall Overhead

Kris Kennaway kris at
Tue Apr 24 04:53:56 UTC 2007

On Mon, Apr 23, 2007 at 09:05:51PM -0700, Tim Kientzle wrote:
> >>>>We can have 3 type of pages mapped into one process's address map.
> >>>>1. System wide global readonly page which will help on these syscalls:
> >>>>gethostname,getdomainname,uname
> >>>>2. Per process Readonly page. (change will still through standard 
> >>>>syscall)
> >>>>help on the syscalls:
> >>>>getuid, geteuid, getpid,getgid, getegid, getpgrp,
> >>
> >>I don't really understand this suggestion.
> >>Do any real programs call these syscalls very often?
> >
> >There is indeed more and more programs calling some syscalls a
> >*lot* ....  MySQL calls gettimeofday() so much that changing
> >the timer used on a system can lead to a very observable performance
> >improvement.  Similarly, PostgreSQL calls setproctitle() a lot  ...
> Accelerating gettimeofday() makes a lot of sense; I've seen a
> lot of programs that call it very often.
> I'm not convinced about calls such as getuid() and gethostname(),
> though.  Putting this kind of information in userspace
> introduces forward-compatibility concerns. People do
> statically link against libc, so you have to make sure that libc can
> find this information even when running on future kernels.
> That makes each such call a tricky maintenance issue.

Well you will have to keep compatibility syscalls anyway, because not
everything even links to libc ;)


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