[igt-dev] FW: [PATCH i-g-t] lib: Incrementally mlock()

[Caz Yokoyama]

Chris,
I dropped v2. Therefore, I replied on v1.

Do you have any idea which achieve 1) not killed, 2) faster,
3) test purpose?
-caz

On Tue, 2019-02-26 at 21:31 +0000, Chris Wilson wrote:
> Quoting Caz Yokoyama (2019-02-26 20:34:01)
> > On Tue, 2019-02-26 at 17:42 +0000, Chris Wilson wrote:
> > > Quoting Yokoyama, Caz (2019-02-26 17:42:51)
> > > > Chris,
> > > > I am OK to give "Reviewed by: XXXX" to your patch.
> > > > However, I want to add following comment/modification which
> > > > does
> > > > not
> > > > affect the effect of your patch.
> > > > 
> > > > +                               /*
> > > > +                                * This is a bug which mlocks
> > > > far
> > > > beyond memory,
> > > > +                                * i.e. there is a hole between
> > > > 3/4
> > > > of
> > > > avail and
> > > > +                                * (bytes * sizeof(*can_mlock))
> > > > where
> > > > +                                * sizeof(*can_mlock)=8.
> > > > Because of
> > > > the
> > > > hole, mlock()
> > > > +                                * may fail and get out of
> > > > while
> > > > loop.
> > > > +                                * However, We need the hole.
> > > > Otherwise
> > > > OOM kills parent
> > > > +                                * process. Another mlock()
> > > > below
> > > > is
> > > > same.
> > > > +                                */
> > > > +                               if (mlock((void *)can_mlock +
> > > > (bytes *
> > > > sizeof(*can_mlock)),
> > > 
> > > But that's a bug in our code, not mlock(). If we try to mlock
> > > more
> > > memory than is available on the system, quite understandably
> > > mlock
> > > fails.
> > > 
> > > So what you are saying here is that you purposely want to not
> > > find
> > > the
> > > limits of mlockable memory.
> > > 
> > > The bug as far as I am concerned was that a subsequent mlock
> > > could
> > > not
> > > claim the same amount of memory as a previous one -- that feels
> > > like
> > > the
> > > mm is not reclaiming everything it can after killing the child,
> > > or at
> > > least not making that available again immediately.
> > > -Chris
> > 
> > Even there was this bug in original code. We have to fix the bug.
> > However, Fixing the bug makes the test die. I proposed a solution.
> > But
> > it destroys the purpose of the test. I have no idea how to achieve
> > both
> > fixing the bug and test porpose.
> 
> You are replying to v1 not v2...
> -Chris