Suggestions on Avoiding syscall Overhead

David G Lawrence dg at
Tue Apr 24 04:48:46 UTC 2007

> >>>>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.

   gettimeofday(2) returns microsecond precision, so I don't see how this
could be made accelerated via a mapped global page. time(3) [which is
currently a wrapper for gettimeofday(2)], on the other had, could be put
into such a page since it only updates once a second.
   Generally, I think that there are enough commonly used syscalls that
would benefit from this that it is probably a good idea - at least a single
system read-only page. I don't think it would be worth wasting a page for
every process for process-specific data, however - the cost of allocating
it, initializing it, etc, for every fork() would be a pessimization in
most cases, I think.


David G. Lawrence
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