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List: openjdk-serviceability-dev
Subject: Re: Low-Overhead Heap Profiling
From: Jeremy Manson <jeremymanson () google ! com>
Date: 2015-08-17 5:03:39
Message-ID: CAPYFHW2Eq696O1bm0JxemhFwoQjhWhQxxHD+t8e3iAP0ES1oDA () mail ! gmail ! com
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Working on it. I hope to have something to share in the next couple of
weeks.
Jeremy
On Wed, Aug 12, 2015 at 4:28 AM, Kees Jan Koster <kjkoster@gmail.com> wrote:
> Guys,
>
> This piqued my interest. Where can I find the draft JEP and the sources
> for this, please?
>
> Kees Jan
>
>
> > On 4 Aug 2015, at 23:22, Jeremy Manson <jeremymanson@google.com> wrote:
> >
> > Thanks, Staffan. I've been tinkering with a draft JEP, but it has been
> going slowly because of other craziness in my life. Some responses:
> >
> > 1) It was a fair bit of work to do it, mostly because it was the first
> time I had tinkered with c2. This was 5 years ago. Most of the work since
> then has been dealing with merge conflicts.
> >
> > 2) I did envision a JVMTI interface. More in the JEP.
> >
> > 3) We have some internal tests, but obviously, we'd have to figure out
> how to externalize them. For native code, it's much easier only to have to
> worry about building and running on Linux. Presumably, there's already
> code in there for JVMTI.
> >
> > I'll try to get a JEP going for real, although it might not happen in
> the next week or so, because I'm moving next week (+the JVMLS).
> >
> > Jeremy
> >
> > On Tue, Aug 4, 2015 at 4:04 AM, Staffan Larsen <
> staffan.larsen@oracle.com> wrote:
> > Hi,
> >
> > Sorry for being away for so long.
> >
> > If memory serves me right then the current AllocObjectInNewTLAB JFR
> event was written as a way to quickly get some allocation profiling
> information with a minimum of VM changes. It probably also carried over to
> Hotspot from JRockit. I agree that we can and should collect better
> information than what that event does.
> >
> > I like the approach of instrumenting the interpreter and compiler to do
> the sampling. I had thought it would be a lot of work to do it and was
> reluctant to go down that path. If the work is already done and Jeremy has
> maintained it for a few years without great problems, I think we should
> look at bringing it in. I am not worried about the overhead of a decrement
> and a compare in the allocation path, but of course we should benchmark
> that.
> >
> > It wasn't clear to me from the discussion how (or if) this was being
> exposed to end users. Was the proposal to just have the native entry points
> in the VM and have these be used by various agents? Would this be part of
> JVMTI?
> >
> > I think a draft JEP would be the logical next step and make it easier
> for us all to discuss what exactly the proposal should contain. Also, let's
> not forget the need for tests for the feature.
> >
> > Thanks,
> > /Staffan
> >
> >
> >
>
>
> --
> Kees Jan
>
> http://java-monitor.com/
> kjkoster@kjkoster.org
> +31651838192
>
> The secret of success lies in the stability of the goal. -- Benjamin
> Disraeli
>
>
[Attachment #3 (text/html)]
<div dir="ltr">Working on it. I hope to have something to share in the next couple \
of weeks.<div><br></div><div>Jeremy</div></div><div class="gmail_extra"><br><div \
class="gmail_quote">On Wed, Aug 12, 2015 at 4:28 AM, Kees Jan Koster <span \
dir="ltr"><<a href="mailto:kjkoster@gmail.com" \
target="_blank">kjkoster@gmail.com</a>></span> wrote:<br><blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex">Guys,<br> <br>
This piqued my interest. Where can I find the draft JEP and the sources for this, \
please?<br> <br>
Kees Jan<br>
<div><div class="h5"><br>
<br>
> On 4 Aug 2015, at 23:22, Jeremy Manson <<a \
href="mailto:jeremymanson@google.com">jeremymanson@google.com</a>> wrote:<br> \
><br> > Thanks, Staffan. I've been tinkering with a draft JEP, but it has \
been going slowly because of other craziness in my life. Some responses:<br> \
><br> > 1) It was a fair bit of work to do it, mostly because it was the first \
time I had tinkered with c2. This was 5 years ago. Most of the work since then \
has been dealing with merge conflicts.<br> ><br>
> 2) I did envision a JVMTI interface. More in the JEP.<br>
><br>
> 3) We have some internal tests, but obviously, we'd have to figure out how \
to externalize them. For native code, it's much easier only to have to worry \
about building and running on Linux. Presumably, there's already code in there \
for JVMTI.<br> ><br>
> I'll try to get a JEP going for real, although it might not happen in the \
next week or so, because I'm moving next week (+the JVMLS).<br> ><br>
> Jeremy<br>
><br>
> On Tue, Aug 4, 2015 at 4:04 AM, Staffan Larsen <<a \
href="mailto:staffan.larsen@oracle.com">staffan.larsen@oracle.com</a>> wrote:<br> \
> Hi,<br> ><br>
> Sorry for being away for so long.<br>
><br>
> If memory serves me right then the current AllocObjectInNewTLAB JFR event was \
written as a way to quickly get some allocation profiling information with a minimum \
of VM changes. It probably also carried over to Hotspot from JRockit. I agree that we \
can and should collect better information than what that event does.<br> ><br>
> I like the approach of instrumenting the interpreter and compiler to do the \
sampling. I had thought it would be a lot of work to do it and was reluctant to go \
down that path. If the work is already done and Jeremy has maintained it for a few \
years without great problems, I think we should look at bringing it in. I am not \
worried about the overhead of a decrement and a compare in the allocation path, but \
of course we should benchmark that.<br> ><br>
> It wasn't clear to me from the discussion how (or if) this was being exposed to \
end users. Was the proposal to just have the native entry points in the VM and have \
these be used by various agents? Would this be part of JVMTI?<br> ><br>
> I think a draft JEP would be the logical next step and make it easier for us all \
to discuss what exactly the proposal should contain. Also, let's not forget the need \
for tests for the feature.<br> ><br>
> Thanks,<br>
> /Staffan<br>
><br>
><br>
><br>
<br>
<br>
</div></div>--<br>
Kees Jan<br>
<br>
<a href="http://java-monitor.com/" rel="noreferrer" \
target="_blank">http://java-monitor.com/</a><br> <a \
href="mailto:kjkoster@kjkoster.org">kjkoster@kjkoster.org</a><br> <a \
href="tel:%2B31651838192" value="+31651838192">+31651838192</a><br> <br>
The secret of success lies in the stability of the goal. -- Benjamin Disraeli<br>
<br>
</blockquote></div><br></div>
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