[ntp:questions] Re: Locking memory in ntp

David Schwartz davids at webmaster.com
Fri Sep 26 20:40:51 UTC 2003

"Michael Sierchio" <kudzu at tenebras.com> wrote in message
news:peGdnSIEpemHyemiRVn-iw at speakeasy.net...

> Maarten Wiltink wrote:

> > Gopal wrote in message ...

> >>Ntpd has a mlockall() function call which locks all the current and
> >>future memory.  Why do we need to lock the memory.

> > To prevent page faults, which can cause unnecessary variation in
> > the response time to receiving timestamps.

> Does it help to point out that mlockall() is a wish and a prayer?
> There are per-process and per-machine limits on how many pages
> may be locked in memory...

> IOW the only guaranteed way of locking all pages in physmem is
> to run without swap.

    Running without swap doesn't guarantee that. In fact, it increases the
chances that pages will be discarded because rarely-used modified pages from
other programs can't be swapped out.


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