RFR(S): 8213086: Compiler thread creation should be bounded by available space in memory and Code Cache
martin.doerr at sap.com
Tue Oct 30 11:46:41 UTC 2018
added comment in place: "If SegmentedCodeCache is off, both values refer to the single heap (with type CodeBlobType::All)."
I have run some tests with -XX:+TraceCompilerThreads -XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI -XX:+UseJVMCICompiler
and also with -XX:-SegmentedCodeCache and all seems to work fine.
Waiting for a 2nd review.
Thanks and best regards,
From: Vladimir Kozlov <vladimir.kozlov at oracle.com>
Sent: Montag, 29. Oktober 2018 19:27
To: Doerr, Martin <martin.doerr at sap.com>; Tobias Hartmann (tobias.hartmann at oracle.com) <tobias.hartmann at oracle.com>
Cc: 'hotspot-compiler-dev at openjdk.java.net' <hotspot-compiler-dev at openjdk.java.net>
Subject: Re: RFR(S): 8213086: Compiler thread creation should be bounded by available space in memory and Code Cache
On 10/29/18 10:13 AM, Doerr, Martin wrote:
> Hi Vladimir,
> thank you for reviewing so quickly.
> unallocated_capacity() doesn't return 0. If SegmentedCodeCache is off, the code cache gets initialized for CodeBlobType::All (codeCache.cpp:1088). Given that, CodeHeap::accepts always returns true (heap.hpp:203) and CodeCache::get_code_heap returns the single heap correctly.
Good. Add comment to avoid confusion.
> But I'm not sure about AOT. Do you know if using CodeCache::unallocated_capacity(CodeBlobType::MethodNonProfiled) is ok if Graal is used?
Normal CodeCache will be present in all cases regardless if Graal or AOT are used.
AOT library code segments have CodeBlobType::AOT type:
So it will not affect your code.
> Best regards,
> -----Original Message-----
> From: Vladimir Kozlov <vladimir.kozlov at oracle.com>
> Sent: Montag, 29. Oktober 2018 17:48
> To: Doerr, Martin <martin.doerr at sap.com>; Tobias Hartmann (tobias.hartmann at oracle.com) <tobias.hartmann at oracle.com>
> Cc: 'hotspot-compiler-dev at openjdk.java.net' <hotspot-compiler-dev at openjdk.java.net>
> Subject: Re: RFR(S): 8213086: Compiler thread creation should be bounded by available space in memory and Code Cache
> So the issue was / 200*M vs correct / (200*M). Thank you for finding and fixing this.
> About taking into account sizes of segmented CodeCache. If segmentation is off (-XX:-SegmentedCodeCache)
> unallocated_capacity() will return 0:
> You need to take that into account.
> On 10/29/18 9:26 AM, Doerr, Martin wrote:
>> Hi Tobias,
>> thank you for filing https://bugs.openjdk.java.net/browse/JDK-8213086
>> I have changed the description because the available memory doesn't get respected due to missing braces. So I'd like to
>> fix this in addition.
>> My test machines have too much memory to hit this case. Maybe I should try to use a docker container for testing.
>> My initial proposal allows up to one compiler thread per 128kB of free code cache. I remember that Oracle wants to have
>> many threads (for some SPARC scenarios) so I have chosen a small size.
>> I'm currently ignoring that C1 also creates some small non-profiled nmethods.
>> Please review:
>> Best regards,
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