[Vm-dev] Unix heartbeat thread vs itimer
Eliot Miranda
eliot.miranda at gmail.com
Tue Mar 21 00:44:11 UTC 2017
Hi David,
On Mon, Mar 20, 2017 at 5:00 PM, David T. Lewis <lewis at mail.msen.com> wrote:
>
> On Mon, Mar 20, 2017 at 09:07:16PM +0100, Levente Uzonyi wrote:
> >
> > IMO the best solution would be to add command line parameters to set the
> > priorities - both main and heartbeat using relative values, and keep the
> > current behavior if none was given. Ben's example would be 0 for both
> > parameters.
> > Then the error message on startup could just say to set one of the
> > parameters to run the VM (e.g. 0,0 or -1,0, etc).
>
> A much simpler solution is to just comment out the "exit(errno)" at line
> 332 of
> sqUnixHearbeat.c. The resulting VM will work fine.
>
Feel free! Do it! Just add a comment to the source.
> If the /etc/security/limits.d/squeak.conf is not in place, then you will
> see
> the annoying but otherwise harmless warming:
>
> pthread_setschedparam failed: Operation not permitted
> This VM uses a thread heartbeat who requires a special configuration to
> work.
> You need to allow it to run higher priority threads (real time), to
> allow clock to work properly
> You need to add a conf file to /etc/security/limits.d, executing this:
>
> sudo cat >/etc/security/limits.d/squeak.conf <<END
> * hard rtprio 2
> * soft rtprio 2
> END
>
>
> Ben's analysis may or may not be exactly right for all conditions of load,
> but
> directionally he is right on target. Clock jitter is of little or no
> interest
> to the general user, and the people who do care about it are fully capable
> of
> setting the necessary security configuration.
>
> > AFAIK you can always decrease the priority of the threads on linux, so 0
> > and negative values should always work.
> >
>
> I think this is correct, so another resonable strategy would be to lower
> the
> priority of threads other than the heartbeat thread when the heartbeat
> priority
> cannot be raised. But if Ben's analysis is generally correct, then it may
> not
> even be worth the trouble of doing that.
>
> Dave
>
--
_,,,^..^,,,_
best, Eliot
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