[Xenomai] Switching to secondary mode despite of use of mmap

Gilles Chanteperdrix gilles.chanteperdrix at xenomai.org
Tue Dec 15 14:59:34 CET 2015

On Tue, Dec 15, 2015 at 11:28:02AM +0000, Umair Ali wrote:
> Hello,
> I am reading a file of size 600 MB using the mmap function and
> mlockall(). My question is that is it possible that mmap has not
> loaded whole file in the memory and if the whole file is not
> loaded then is it changing to secondary mode while reading the
> file.

Unless you have not passed MCL_CURRENT | MCL_FUTURE to mlockall or
did not check mlockall return value and mlockall in fact failed, this
is impossible.

>The size of system heap is 256KB in the menuconfig for the
> compiling kernel.

The size of the system heap has nothing to do with mlockall.

> If the problem, i think, i have is true then how
> i can load the such big files using mmap. The output of slackspot
> is attached with this email. My system specs are Memory 3.1GiB and
> processor is intel P4 3.2GHz x 2.

The slackspot trace you show only contains calls to timerfd_create
and socket. Yes, timerfd_create and socket cause a switch to
secondary mode.


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