diff options
| -rw-r--r-- | lib/hipe/doc/src/hipe_app.xml | 62 |
1 files changed, 52 insertions, 10 deletions
diff --git a/lib/hipe/doc/src/hipe_app.xml b/lib/hipe/doc/src/hipe_app.xml index fc42ecd97d..4d40db086c 100644 --- a/lib/hipe/doc/src/hipe_app.xml +++ b/lib/hipe/doc/src/hipe_app.xml @@ -35,6 +35,14 @@ <app>HiPE</app> <appsummary>The HiPE Application</appsummary> <description> + <note> + <p> + HiPE and execution of HiPE compiled code only have limited support by + the OTP team at Ericsson. The OTP team only does limited maintenance + of HiPE and does not actively develop HiPE. HiPE is mainly supported + by the HiPE team at Uppsala University. + </p> + </note> <p> The normal way to native-compile an Erlang module using HiPE is to include the atom native in the Erlang compiler options, as in:</p> @@ -108,7 +116,7 @@ queue when the reference was created will be bypassed, as they cannot possibly contain the reference. HiPE currently has an optimization similar this, but it is not guaranteed to - bypass all messages. In the worst case scenario it, cannot + bypass all messages. In the worst case scenario, it cannot bypass any messages at all. </p> <p> @@ -117,21 +125,55 @@ </p> </item> + <tag>Garbage collection after BIFs</tag> + <item> + <p> + The condition for determining whether a garbage collection + is needed or not has changed in later releases. HiPE has not + been updated regarding this which may cause premature garbage + collections after BIF calls. + </p> + </item> + </taglist> </section> <section> <title>Stability Issues</title> <taglist> - <tag>Not yielding in <c>receive</c> statements</tag> + <tag>Not checking reduction count on function returns</tag> <item> - <p>HiPE will not yield in <c>receive</c> statements where - appropriate. If a process have lots of signals in its signal - queue and execute a HiPE compiled <c>receive</c> statement, - the scheduler thread performing the execution may be stuck - in the <c>receive</c> statement for a very long time. This - can in turn cause various severe issues such as for example - prevent the runtime system from being able to release - memory. + <p> + BEAM checks the reduction count and schedules out the executing + process if needed both when calling a function and when returning + from a function call that was not called using a tail call. + HiPE only checks the reduction count when calling a function. + </p> + <p> + The runtime system might need to schedule out a process + in order to reclaim memory. If the process isn't scheduled + out soon after the process has entered this state, memory + consumption will quickly grow. Maintaining this state is also + quite expensive performance wise. + </p> + <p> + Processes executing code that performs large recursions and + produce data after returning from recursive calls may have to + be scheduled out when returning from a function call. Since + HiPE does not check reductions on returns, processes executing + such HiPE compiled code may cause huge peeks in memory + consumption as well as severe performance degradation. + </p> + </item> + + <tag>Not bumping appropriate amount of reductions in <c>receive</c> statements</tag> + <item> + <p> + The process signaling improvements made in ERTS version + 10.0 moved potentially significant amounts of work into the + receive statement from other places. In order to account for + this work, the reduction count should be bumped on the + executing process. Reductions are not bumped when entering + the <c>receive</c> statement from HiPE compiled code. </p> </item> </taglist> |