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<br>
Ramki,<br>
<br>
Thanks for the extra testing!<br>
<br>
Jon, John and Tony,<br>
<br>
Thanks for the reviews! Are you OK with pushing this (handle values
< 1 as never force full compaction):<br>
<a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~brutisso/7110718/webrev.03/">http://cr.openjdk.java.net/~brutisso/7110718/webrev.03/</a><br>
<br>
Instead of this (forbid values < 1):<br>
<a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~brutisso/7110718/webrev.02/">http://cr.openjdk.java.net/~brutisso/7110718/webrev.02/</a><br>
<br>
I think your review comments were more related to webrev.02, so I
would like to double check with you before I push my changes in
webrev.03.<br>
<br>
Thanks,<br>
Bengt<br>
<br>
<br>
On 2011-11-18 08:11, Srinivas Ramakrishna wrote:
<blockquote
cite="mid:CABzyjymetvJfuZF_bTAh_sTc3Kc8BrfQmfUDRTTwCVBtxyFPmw@mail.gmail.com"
type="cite">Hi Bengt -- this looks good to me. It also passed my
testing...<br>
I also confirmed what Jon indicated -- that VerifyUpdateClosure is
dead code, as far as my cscope<br>
navigation showed and can be deleted (in a separate CR as Jon
said).<br>
<br>
Rebiewed; thanks!<br>
-- ramki<br>
<br>
<div class="gmail_quote">On Thu, Nov 17, 2011 at 6:13 AM, Bengt
Rutisson <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:bengt.rutisson@oracle.com">bengt.rutisson@oracle.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div bgcolor="#ffffff" text="#000000"> <br>
Hi Ramki,<br>
<br>
Is this what you were considering?<br>
<a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Ebrutisso/7110718/webrev.03/"
target="_blank">http://cr.openjdk.java.net/~brutisso/7110718/webrev.03/</a><br>
<br>
I think it should interpret MarkSweepAlwaysCompactCount
<= 0 as "never force full compaction". It would be great
if you could do some testing. There is one assert in
PSParallelCompact::VerifyUpdateClosure::do_addr() that
worries me a bit:<br>
<br>
assert(HeapMaximumCompactionInterval > 1 ||
MarkSweepAlwaysCompactCount > 1 ||<br>
forwarding_ptr == new_pointer, "new location is
incorrect");<br>
<br>
I think this should be safe since
MarkSweepAlwaysCompactCount == 1 was an acceptable value
even before my change. But I have to admit that I don't
really understand what the assert is trying to verify.<br>
<font color="#888888"> <br>
Bengt</font>
<div>
<div class="h5"><br>
<br>
<br>
On 2011-11-16 19:01, Srinivas Ramakrishna wrote:
<blockquote type="cite">Hi Bengt, Not sure how much
customers use this option. Its useful for
"serviceability in production" kind of scenarios<br>
to have the code be more robust. I think it would be
useful. I appreciate the need for more testing<br>
of course, and I am happy to do that testing for you
-- just let me know and I'll grab yr patch and test<br>
here.<br>
<br>
thanks!<br>
-- ramki<br>
<br>
<div class="gmail_quote">On Tue, Nov 15, 2011 at 6:50
AM, Bengt Rutisson <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:bengt.rutisson@oracle.com"
target="_blank">bengt.rutisson@oracle.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0pt
0pt 0pt 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> <br>
Ramki,
<div><br>
<br>
On 2011-11-14 20:32, Srinivas Ramakrishna
wrote:
<blockquote type="cite"><br>
Thanks, Bengt, for the super-quick
turnaround!! A comment below on the choice
of <= 0 for the option value....<br>
</blockquote>
<br>
</div>
Thanks for the review! See comments below.
<div><br>
<br>
<blockquote type="cite">
<div class="gmail_quote">On Mon, Nov 14,
2011 at 1:25 AM, Bengt Rutisson <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:bengt.rutisson@oracle.com" target="_blank">bengt.rutisson@oracle.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0pt 0pt 0pt
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex"><br>
Hi all,<br>
<br>
Can I have a couple of reviews for this
small change?<br>
<a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Ebrutisso/7110718/webrev.01/"
target="_blank">http://cr.openjdk.java.net/~brutisso/7110718/webrev.01/</a><br>
<br>
It is a fix for the issue that Ramki
reported recently.
MarkSweepAlwaysCompactCount is used for
division and Hotspot crashes if it is
set to 0.<br>
<br>
I choose to log an error and exit the VM
if someone tries to start with
-XX:MarkSweepAlwaysCompactCount=0. An
alternative is to just log a warning and
set it to 1.<br>
<br>
I prefer the error way since it is not
really clear what one wants to achieve
with MarkSweepAlwaysCompactCount=0.
Always do full compactions or never do
full compactions? So I am not convinced
that 1 is an appropriate value.<br>
<br>
Also, since the VM, up until now, has
crashed if someone tried
-XX:MarkSweepAlwaysCompactCount=0 I
think we can be sure that there are no
customers that are running with that
setting. It should be safe to forbid it.<br>
</blockquote>
<div><br>
I agree with that statement. However,
given that the value 0 was producing
crashes, proving that no production code
would have been using that setting,<br>
and based on yr comment above that the 0
value could as well have been used to
denote "never force full compaction", it
seems as though an alternative to
exiting with<br>
an error, is now to define all values
<=0 to mean "never _force_ full
compaction" <br>
<br>
Especially since tolerating allowed
input values and mapping them to
specific non-exiting behaviours allows
us to modify production JVM's on the fly<br>
without causing loss of availability.
(Consider a future in which this option
becomes a "manageable"; you would then
be faced with the same<br>
question, and it seems as though making
this choice now would help maintain
consistency and robustness going forward
-- we could of course<br>
always throw a "illegal value exception"
or such at that point, but allowing the
specification of "never _force_ full
compaction" (unless the JVM<br>
otherwise chooses to) would appear to be
a choice to allow users; mapping
negative and 0 values to that setting
would avoid having to<br>
throw an error.) However, I understand
that this is somewhat subjective, so I
am willing to go with whatever the
majority consensus here<br>
mght be. It just seemed more pleasant
to:<br>
(1) allow the specification of
reasonable behaviour (i.e. never _force_
...)<br>
(2) map the full domain of the option to
a reasonable behaviour (i.e. allow <=
0 to map to never _force_ ..)<br>
<br>
Comments?<br>
</div>
</div>
</blockquote>
<br>
</div>
I see your point, and I think this should be
fairly straight forward to fix. However it will
require some more testing etc. I can do that,
but I don't think I know enough to say whether
or not the extra work is worth it. How important
is this option? Is it something that customers
use a lot?<br>
<br>
Thanks,<br>
<font color="#888888"> Bengt</font>
<div><br>
<br>
<blockquote type="cite">
<div class="gmail_quote">
<div><br>
-- ramki<br>
<br>
<br>
</div>
<blockquote class="gmail_quote"
style="margin:0pt 0pt 0pt
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex"> <br>
CR:<br>
<br>
7110718
-XX:MarkSweepAlwaysCompactCount=0
crashes the JVM<br>
<a moz-do-not-send="true"
href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7110718"
target="_blank">http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7110718</a><br>
<br>
Thanks,<br>
<font color="#888888"> Bengt<br>
</font></blockquote>
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