On Tue, Dec 21, 2021 at 06:42:04AM +0800, Zhouyi Zhou wrote:
> Thanks Paul and Akira
>
> great improvement to perfbook's glossary!
>
> A question below ;-)
>
> On Tue, Dec 21, 2021 at 4:15 AM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
> >
> > On Mon, Dec 20, 2021 at 06:55:36PM +0900, Akira Yokosawa wrote:
> > > Hi Paul,
> > >
> > > While reading through Section 9.5.4, I noticed a few terms
> > > I'd like to see in perfbook's Glossary.
> > >
> > > - Reference Counter/Counting
> > > - Existence Guarantee
> > > - Type-safe Memory
> > >
> > > "Reference counter" is already mentioned in a couple of existing
> > > items in the glossary.
> > >
> > > "Existing guarantee" might be obvious enough and not worthy
> > > to be in the glossary.
> > >
> > > Thoughts?
> > >
> > > There were only a few minor nits in the section.
> > > Will post a patch taking care of them.
> >
> > Thank you for looking it over! Please see below for a proposed patch
> > to the glossary. Oh, and thank you for the checking utilities, very
> > nice to get explicit messages rather than subtlely broken formatting!!!
> >
> > utilities/punctcheck.sh
> > ./glossary.tex:547: Type-safe memory\cite{Cheriton96a} is provided by a
> > utilities/cleverefcheck.sh
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > commit a8f5948a1b8921941bf4039e278aa7929f64c322
> > Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
> > Date: Mon Dec 20 09:41:55 2021 -0800
> >
> > glossary: Add reference count, existence guarantee, and TSM
> >
> > Where "TSM" is type-safe memory.
> >
> > Reported-by: Akira Yokosawa <akiyks@xxxxxxxxx>
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> >
> > diff --git a/glossary.tex b/glossary.tex
> > index be10f703..31c09232 100644
> > --- a/glossary.tex
> > +++ b/glossary.tex
> > @@ -199,6 +199,14 @@
> > increase the overall cost of the computation, resulting in
> > linear speedups as threads are added (assuming sufficient
> > CPUs are available).
> > +\item[\IX{Existence Guarantee}:]
> > + An existence guarantee is provided by a synchronization mechanism
> > + that prevents a given dynamically allocated object from being
> > + freed for the duration of that guarantee.
> > + For example, RCU provides existence guarantees for the duration
> > + of RCU read-side critical sections.
> > + A similar but strictly weaker guarantee is provided by
> > + type-safe memory.
> here type-safe memory is called 'weaker'
Type-safe memory is weaker than existence guarantees ...
> > \item[\IXh{Exclusive}{Lock}:]
> > An exclusive lock is a mutual-exclusion mechanism that
> > permits only one thread at a time into the
> > @@ -469,6 +477,11 @@
> > A situation in which getting the correct result is not sufficient,
> > but where this result must also be obtained within a given amount
> > of time.
> > +\item[\IX{Reference Count}:]
> > + A counter that tracks the number of users of a given object or
> > + entity.
> > + Reference counters provide existence guarantees and are sometimes
> > + used to implement garbage collectors.
> > \item[\IX{Scalability}:]
> > A measure of how effectively a given system is able to utilize
> > additional resources.
> > @@ -531,6 +544,17 @@
> > A synchronization mechanism that gathers groups of memory
> > accesses so as to execute them atomically from the viewpoint
> > of transactions on other CPUs or threads.
> > +\item[\IX{Type-Safe Memory}:]
> > + Type-safe memory~\cite{Cheriton96a} is provided by a
> > + synchronization mechanism that prevents a given dynamically
> > + allocated object from changing to an incompatible type.
> > + Note that the object might well be freed and then reallocated, but
> > + the reallocated object is guaranteed to be of a compatible type.
> > + Within the Linux kernel, type-safe memory is provided within
> > + RCU read-side critical sections for memory allocated from slabs
> > + marked with the \co{SLAB_TYPESAFE_BY_RCU} flag.
> > + The strictly stronger existence guarantee also prevents freeing
> > + of the protected object.
>
> but why do we use "stronger" here (should not it be "weaker"?)
... Or, alternatively but equivalently, existence guarantees are stronger
than type-safe memory.
Is there a better way to word this?
Thanx, Paul
> > \item[\IX{Unteachable}:]
> > A topic, concept, method, or mechanism that the teacher does
> > not understand well is therefore uncomfortable teaching.
> Many thanks
> Zhouyi
