RFR(XS) 8031065: LowMemoryTest2.sh fails: OutOfMemoryError: Metaspace

[Mattias Tobiasson]

Daniel, could you please sponsor this fix?

Mattias

----- Original Message -----
From: daniel.fuchs at oracle.com
To: mattias.tobiasson at oracle.com, shanliang.jiang at oracle.com
Cc: serviceability-dev at openjdk.java.net
Sent: Friday, February 28, 2014 12:05:47 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
Subject: Re: RFR(XS) 8031065: LowMemoryTest2.sh fails: OutOfMemoryError: Metaspace

Hi Mattias,

The new version looks good!

best regards,

-- daniel

On 2/28/14 11:33 AM, Mattias Tobiasson wrote:
> Hi,
> I have updated the test and now stop allocating when we have reached the threshold.
> Since we now do all allocations first and then just wait for the notification, I have split the loop into two separate loops to make it clearer.
>
> To detect if we have reached the threshold I now check MemoryPoolMXBean.getUsageThresholdCount() > 0 instead of checking isUsageThresholdExceeded().
> The reason for that is because the notification event is not generated immediately when isUsageThresholdExceeded() = true. The notification is only generated at the next GC. So that is the reason for why the old test kept allocating after it had reached the threshold (to trigger another GC).
>
> getUsageThresholdCount() is updated at the same time as the event is generated. So after getUsageThresholdCount() > 0, I can just wait for the notification without more allocations.
>
> webrev:
> http://cr.openjdk.java.net/~mtobiass/8031065/webrev.01
>
> bug:
> https://bugs.openjdk.java.net/browse/JDK-8031065
>
> Mattias
>
> ----- Original Message -----
> From: shanliang.jiang at oracle.com
> To: mattias.tobiasson at oracle.com
> Cc: serviceability-dev at openjdk.java.net, daniel.fuchs at oracle.com
> Sent: Thursday, February 27, 2014 5:12:51 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
> Subject: Re: RFR(XS) 8031065: LowMemoryTest2.sh fails: OutOfMemoryError: Metaspace
>
>
> Mattias Tobiasson wrote:
>
> Hi, thanks for the fast reviews.
>
> I did think about stop calling loadNext() after the flag has been set. The main reason for not doing that was just because I wanted to change as little as possible. Now the test works as originally intended. I prefer to do like this too :)
>
>
> I do not mind removing the calls to loadNext(), but then we would need some timeout waiting for the callback. Currently the test "times out" with an OutOfMemory when we have allocated the remaining 20% of the space. You do not need to add a timeout, only change Line 151
> for(;;)
> to
> while(!listenerInvoked) {
>
> and remove 160 -- 162
>
> in case that an expected notification is not arrived, the testing harness has a timeout to stop the test.
>
> This way makes the test more robust, but I am OK with the current fix.
>
> Thanks,
> Shanliang
>
>
> About line 172, you are correct. I will just remove that line. Thanks!
>
> Mattias
>
> ----- Original Message -----
> From: shanliang.jiang at oracle.com To: daniel.fuchs at oracle.com Cc: mattias.tobiasson at oracle.com , serviceability-dev at openjdk.java.net Sent: Thursday, February 27, 2014 12:59:49 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
> Subject: Re: RFR(XS) 8031065: LowMemoryTest2.sh fails: OutOfMemoryError: Metaspace
>
> Daniel Fuchs wrote:
>
> On 2/27/14 11:43 AM, Mattias Tobiasson wrote:
>
> Hi,
> Could you please review this test fix.
>
> The test verifies that MemoryPoolMXBean sends a notification when
> used memory has reached the threshold.
> The flag thresholdExceeded marks if we have reached the memory
> threshold. When the flag is set, the test slows down to give time for
> the notification to be received.
> The problem is that thresholdExceeded is overwritten every time in
> the loop. Instead it should be set if any pool has reached the
> threshold. This means that the test continues to allocate memory at
> full speed, and we may get an OutOfMemory before we get the
> notification. Hi Mattias,
>
> I wonder whether you should also stop calling loadNext() once
> thresholdExceeded is true? Yes I am thinking this too.
>
> Line 172 is unnecessary, after thresholdExceeded becomes true, Line 170
> will always be skipped.
>
> Shanliang
>
> best regards,
>
> -- daniel
>
> bug: https://bugs.openjdk.java.net/browse/JDK-8031065 webrev: http://cr.openjdk.java.net/~ykantser/8031065/webrev.00/ Mattias
>

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