Changeset 970fa54 for doc/theses/thierry_delisle_PhD

Timestamp:

Jul 25, 2022, 11:47:36 AM (2 years ago)

Author:

Thierry Delisle <tdelisle@…>

Branches:

ADT, ast-experimental, master, pthread-emulation, qualifiedEnum

Children:

8fe35be

Parents:

6a6544d (diff), 24a3d2b (diff)
Note: this is a merge changeset, the changes displayed below correspond to the merge itself.
Use the (diff) links above to see all the changes relative to each parent.

Message:

Merge branch 'master' of plg.uwaterloo.ca:software/cfa/cfa-cc

File:

• doc/theses/thierry_delisle_PhD/thesis/text/practice.tex (modified) (2 diffs)

doc/theses/thierry_delisle_PhD/thesis/text/practice.tex

@@ -199 +199 @@
 Interestingly, general notification, \ie waking any idle processor versus a specific one, does not strictly require modifying the list.
 Here, contention can be reduced notably by having notifiers avoid the lock entirely by adding a pointer to the event @fd@ of the first idle \proc, as in Figure~\ref{fig:idle2}.
-To avoid contention among notifiers, notifiers atomically exchange it to @NULL@ so only one notifier contends on the system call.
-The first notifier will succeed the atomic exchange and obtain the @fd@ of an idle \proc.
-The notifier will the normally write to the @fd@, which will wake a \proc.
-The woken \proc can then update the atomic pointer while it is updating the head of the list.
-Notifiers that obtained a @NULL@ in the exchange simply move on, knowing that another notifier is already waking a \proc.
+To avoid contention among notifiers, notifiers atomically exchange the pointer with @NULL@.
+The first notifier succeeds on the exchange and obtains the @fd@ of an idle \proc;
+hence, only one notifier contends on the system call.
+This notifier writes to the @fd@ to wake a \proc.
+The woken \proc then updates the atomic pointer, while it is updating the head of the list, as it removes itself from the list.
+Notifiers that obtained a @NULL@ in the exchange simply move on knowing that another notifier is already waking a \proc.
 This behaviour is equivalent to having multiple notifier write to the @fd@ since reads consume all previous writes.
 Note that with and without this atomic pointer, bursts of notification can lead to an unspecified number of \procs being woken up, depending on how the arrival notification compares witht the latency of \procs waking up.
@@ -217 +218 @@
 
 The next optimization is to avoid the latency of the event @fd@, which can be done by adding what is effectively a binary benaphore\cit{benaphore} in front of the event @fd@.
-A simple three state flag is added beside the event @fd@ to avoid unnecessary system calls, as shown in Figure~\ref{fig:idle:state}.
+The benaphore over the event @fd@ logically provides a three state flag to avoid unnecessary system calls, where the states are expressed explicit in Figure~\ref{fig:idle:state}.
 A \proc begins its idle sleep by adding itself to the idle list before searching for an \at.
 In the process of adding itself to the idle list, it sets the state flag to @SEARCH@.