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<p>Hi Sebastien,</p>
<p>Thank you for providing your insights! Please see my response
in-line:</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 3/12/25 7:47 AM, Sebastien Deleuze
wrote:<br>
</div>
<blockquote type="cite" cite="mid:CAG5jep-yJfHLjzEhh30Kjs53ME58p2xnGvS3wFu=ARY5XD=j2Q@mail.gmail.com">
<div dir="ltr">Those 3 alternatives make sense from my POV and
look complementary:<br>
- JCMD could be used by sysops and for testing.<br>
- API could potentially be used by a Spring Boot actuator [1]
exposing a secured endpoint allowing to trigger the end of a
training run.<br>
- Commandline could be useful for platforms wanting to provide
AOT cache support with the knowledge of the frameworks used. For
example, it could be used to specify
`-XX:CDSEndTrainingOnEntry=org.springframework.web.servlet.DispatcherServlet#doService`
after 10000 invocations.<br>
<br>
If that's a new capability, would it make sense to only expose
it via `-XX:AOTEndTrainingOnEntry` instead of
`-XX:CDSEndTrainingOnEntry` to avoid too many options and some
confusion?<br>
<br>
</div>
</blockquote>
<p>Sorry I cut-and-pasted the text from the bug report without
updating it to use the new "AOT" terminology. In the Leyden repo,
this option is already changed to -XX:<span style="color: rgb(23, 43, 77); font-family: "DejaVu Sans", sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">AOTEndTrainingOnMethodEntry.
<br>
</span></p>
<p><br>
</p>
<blockquote type="cite" cite="mid:CAG5jep-yJfHLjzEhh30Kjs53ME58p2xnGvS3wFu=ARY5XD=j2Q@mail.gmail.com">
<div dir="ltr">Providing those capabilities will be very important
when AOT profiles and AOT compiled methods will be available as
they could allow target use cases where the production
environment is used to get profiling data (will be the most
popular use case IMO), and you would typically want to dump the
profiling data without killing the instance. That said, it could
maybe ease integrators' work to support those capabilities
earlier than AOT profiles and AOT compiled methods, if that
makes sense with the current feature set. For example, it could
allow platforms and frameworks to be "Leyden-ready" with a Java
25 minimal requirement if we consider those JCMD/API/Commandline
as a subset of "Leyden public API". AOT profiles and AOT
compiled methods support could come later and be almost an
implementation detail from platforms and frameworks POV.<br>
<br>
Since the creation of an AOT cache with Spring Petclinic was
pretty long and resource consuming last time I tried, I am
wondering if it could be possible to provide an option to
control what kind of output we expect at the end of the training
run. Generating directly the CDS/AOT archive makes sense, but on
production it could be potentially too resource consuming and
would produce too many side effects. Like the JEP 483
differentiates the AOT configuration recorded (app.aotconf) from
the cache (app.aot), would it be possible with AOT profiles and
AOT compiled methods to optionally generate an intermediate
format that would be fast to generate at the end of the
training, and defer the more involved creation of the archive at
a later point (keeping the constraints of same OS, Java version
and classpath)?<br>
</div>
<br>
</blockquote>
<p><br>
</p>
<p>We plan to support the intermediate form (app.aotconf) going
forward, so you will be able to record that on a small host. This
file can be transferred to a bigger development host to create the
final AOT cache (with metadata, profiles and compiled methods).<br>
</p>
<p>Thanks</p>
<p>- Ioi<br>
</p>
<p><br>
</p>
<p><br>
</p>
<blockquote type="cite" cite="mid:CAG5jep-yJfHLjzEhh30Kjs53ME58p2xnGvS3wFu=ARY5XD=j2Q@mail.gmail.com">
<div class="gmail_quote gmail_quote_container">
<div dir="ltr" class="gmail_attr">On Thu, Mar 6, 2025 at 9:23 PM
<<a href="mailto:ioi.lam@oracle.com" moz-do-not-send="true" class="moz-txt-link-freetext">ioi.lam@oracle.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p>With JEP 483 [1], the profiling data (AOT config file)
are captured when the training run exits. In the Leyden
repo, we have implemented a mechanism [2] to capture the
profiler data at an earlier point. Excerpt from [2]:</p>
<p><br>
</p>
<p>===</p>
<p><span style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">It
may be difficult for users to run to normal completion
for all training runs - some may prefer to only record
data until the application framework has started or
prior to some method being invoked.</span><br style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">
<br style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">
<span style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">This
RFE is to track other possible triggers for CDS data to
be collected and / or for the _assembly phase_ to being.</span><br style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">
<br style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">
<span style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">(a)
JCMD: a new jcmd can be developed to attach to a running
JVM and signal the training run has ended. For classic
CDS, this may be the point at which the classlist is
dumped to the file. For premain CDS, this may trigger
the start of the assembly phase and the creation of the
CDS archive.</span><br style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">
<br style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">
<span style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">(b)
API: a new Leyden-specific API may be created that
allows developers to indicate programatically the point
at which the training run should end. This could be as
simple as a static method `Leyden.endTraining()` or
something that exposes more state such as the name of
the CDS file. Details TBD based on need.</span><br style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">
<br style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial">
<span style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">(c)
Commandline: a new option could specify when to trigger
the end of the training run. ie:
`-XX:CDSEndTrainingOnEntry=org.foo.bar.someMethod`. This
can be extended beyond single entry to also include a
counted entry ie: the 1000 time this method is entered.</span></p>
<p><span style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">===<br>
</span></p>
<p><span style="color:rgb(23,43,77);font-family:"DejaVu Sans",sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;word-spacing:0px;white-space:normal;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><br>
</span></p>
<p>As of today, (a) and (c) have been implemented in the
Leyden repo. We have received positive feedback from
developers who found this mechanism to be useful and are
requesting for similar features in the JDK mainline.</p>
<p>I think now will be a good time to have a wider
discussion with the community about:</p>
<p>- The use case and requirements for such a mechanism</p>
<p>- The solution space -- besides the 3 options listed
above, are there other approaches? Pros & cons?</p>
<p>For example, an API might be more precise. However, many
apps are built with 3rd libraries that cannot be modified
easily, so an external mechanism would be preferable. JCMD
might be least intrusive, but it's timing dependent and
may not be available (in containers, etc).<br>
</p>
<p><br>
</p>
<p>--------------------------------------<br>
</p>
<p>[1] <a href="https://openjdk.org/jeps/483" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">https://openjdk.org/jeps/483</a><br>
</p>
<p>[2] <a href="https://bugs.openjdk.org/browse/JDK-8335358" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">https://bugs.openjdk.org/browse/JDK-8335358</a><br>
</p>
</div>
</blockquote>
</div>
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