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.
\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.
\item[\IX{Unteachable}:]
A topic, concept, method, or mechanism that the teacher does
not understand well is therefore uncomfortable teaching.
