February 2018 - core-libs-dev

Draft JEP: Enhanced pseudo-random number generators
by Guy Steele 23 May '19

23 May '19

Please check out a new draft JEP https://bugs.openjdk.java.net/browse/JDK-8193209 <https://bugs.openjdk.java.net/browse/JDK-8193209> that proposes new interface types and implementations for pseudo-random number generators. —Guy

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Re: RFR: 8198526: getAnnotatedOwnerType does not handle static nested classes correctly
by Liam Miller-Cushon 20 Dec '18

20 Dec '18

(replying to edit the subject) On Wed, Feb 21, 2018 at 2:18 PM, Liam Miller-Cushon <cushon(a)google.com> wrote: > Hello, > > Please review this fix to the handling of static nested classes > in getAnnotatedOwnerType. > > webrev: http://cr.openjdk.java.net/~cushon/8198526/webrev.00/ > bug: https://bugs.openjdk.java.net/browse/JDK-8198526 >

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The new optimized version of Dual-Pivot Quicksort
by Vladimir Yaroslavskiy 20 Nov '18

20 Nov '18

Hi team, In Sept 2009 Josh Bloch, Jon Bentley and I introduced new sorting algorithm, Dual-Pivot Quicksort, for primitives in JDK 7 and later I suggested several improvements of Dual-Pivot Quicksort, which were integrated into JDK 8. Now I have more optimized and faster version of Dual-Pivot Quicksort. I have been working on it for the last 5 years. Please, find the summary of changes below and sources / diff at webrev [1]. All tests and benchmarking were run on the most recent build of JDK 10, jdk-10-ea+39. The new version shows the better performance on different inputs and guarantees n*log(n) on any data. The new implementation of Dual-Pivot Quicksort is 'all-in-one' version: it contains one code for both parallel and sequential sorting algorithms. Suggested version is 10-20% faster on random data, 1.5-4 times faster on nearly structured arrays, 1.5-2 times faster on period inputs. Parallel Dual-Pivot Quicksort is 1.5-3 times faster than current algorithm based on merge sort. Benchmarking on the test suite, suggested by Jon Bentley, shows the boost of performance in 1.4 times. This test suite contains several types of inputs, such as random data, nearly structured arrays, data with period and so on. Also there are several modifications of inputs and parameters which are used in data building. We run sorting on all combinations to compare two algorithms. Please let me know if you have any questions / comments. Summary of changes: DualPivotQuicksort class ------------------------ * Pivots are chosen with another step, the 1-st and 5-th candidates are taken as pivots instead of 2-nd and 4-th. * Splitting into parts is related to the golden ratio * Pivot candidates are sorted by combination of 5-element network sorting + insertion sort * New backwards partitioning is simpler and more efficient * Quicksort tuning parameters were updated * Merging sort is invoked on each iteration from Quicksort * Additional steps for float/double were fully rewritten * Heap sort is invoked on the leftmost part * Heap sort is used as a guard against quadratic time * Parallel sorting is based on Dual-Pivot Quicksort instead of merge sort SortingAlgorithms class ----------------------- * Merging sort and pair insertion sort were moved from DualPivotQuicksort class * Pair insertion sort was simplified and optimized * New nano insertion sort was introduced for tiny arrays * Merging sort was fully rewritten * Optimized merging partitioning is used * Merging parameters were updated * Merging of runs was fully rewritten * Fast version of heap sort was introduced * Parallel merging sort was also provided Sorting / ParallelSorting classes --------------------------------- * New test cases were added * Sources of these classes were unified Arrays class ------------ * Calls of Dual-Pivot Quicksort were updated * Parallel sorting of primitives was switched to parallel Dual-Pivot Quicksort * Javadoc was modified ArraysParallelSortHelpers class ------------------------------- * Old implementation of parallel sorting for primitives was removed * Javadoc was updated Thank you, Vladimir -------------------------------------------------------------------- [1] http://cr.openjdk.java.net/~alanb/DualPivotSortUpdate/webrev.01/ --------------------------------------------------------------------

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Reactive Streams utility API
by James Roper 28 Sep '18

28 Sep '18

Hi all, This is an email to give people a heads up that we'd like to look at creating an API, in the same vein as the JDK8 Streams API, for building reactive streams (a la JDK9 juc.Flow). Our goals for this are: * To fill a gap in the JDK where if a developer wants to do even the simplest of things with a JDK9 juc.Flow, such as map or filter, they need to bring in a third party library that implements that. * To produce an API that can build Publishers, Subscribers, Processors, and complete graphs, for the purposes of consuming APIs that use reactive streams (for example, JDK9 Http Client). * To produce an API that aligns closely with ju.stream.Stream, using it for inspiration for naming, scope, general API shape, and other aspects. The purpose of this goal is to ensure familiarity of Java developers with the new API, and to limit the number of concepts Java developers need to understand to do the different types of streaming offered by the JDK. * To produce an API that can be implemented by multiple providers (including an RI in the JDK itself), using the ServiceLoader mechanism to provide and load a default implementation (while allowing custom implementations to be manually provided). There are a lot of concerns that each different streams implementation provides and implements, beyond streaming, for example monitoring/tracing, concurrency modelling, buffering strategies, performance aspects of the streams handling including fusing, and context (eg thread local) propagation. This will allow libraries to use and provide contracts based on this API without depending on a particular implementation, and allows developers to select the implementation that meets their needs. Non goals: * To produce a kitchen sink of utilities for working with reactive streams. There already exist a number of reactive streams implementations that seek to meet this goal (eg, Akka Streams, Reactor, RxJava), and once you go past the basics (map, filter, collect), and start dealing with things like fan in/out, cycles, restarting, etc, the different approaches to solving this start to vary greatly. The JDK should provide enough to be useful for typical every day streaming use cases, with developers being able to select a third party library for anything more advanced. We will update this list when we have something ready for public review. This probably won't be far off. Our hope is that we can propose this as a JEP. Regards, James -- *James Roper* *Senior Octonaut* Lightbend <https://www.lightbend.com/> – Build reactive apps! Twitter: @jroper <https://twitter.com/jroper>

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RFR 7183985: Class.getAnnotation() throws an ArrayStoreException when the annotation class not present
by Liam Miller-Cushon 15 Jun '18

15 Jun '18

Hello, Please consider this fix for JDK-7183985. bug: https://bugs.openjdk.java.net/browse/JDK-7183985 webrev: http://cr.openjdk.java.net/~cushon/7183985/webrev.01/ I started a CSR for the change: https://bugs.openjdk.java.net/browse/JDK-8198584 We have been using the fix at Google for about two years, and there has been no compatibility impact. I found very few places ArrayStoreException was being explicitly handled, and none that were depending on the current behaviour of getAnnotation(). There was some previous discussion of the bug on core-libs-dev: * http://mail.openjdk.java.net/pipermail/core-libs-dev/2016-April/040590.html * http://mail.openjdk.java.net/pipermail/core-libs-dev/2013-October/021798.ht… Thanks, Liam

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Patch fixing JDK-8176553
by Jan Kalina 04 Apr '18

04 Apr '18

Hi, I has prepared trivial patch for bug JDK-8176553, which I has reported. I will welcome if it could be merged into JDK. (The bug is present in JDK9 and JDK8 too.) I am covered by Red Hat OCA. The patch is attached, bug reproducer is already in JIRA: https://bugs.openjdk.java.net/browse/JDK-8176553 Thanks, Jan Kalina

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[10?] RFR: 8193128: Reduce number of implementation classes returned by List/Set/Map.of()
by Claes Redestad 26 Mar '18

26 Mar '18

Hi, please help review this patch to consolidate the number of implementation classes returned by the static collection factories: http://cr.openjdk.java.net/~redestad/8193128/open.00/ I set out to explore options for addressing small inefficiencies we've been running into, the latest after replacing use of @Stable arrays in java.lang.invoke with List.of() (JDK-8184777): - List.indexOf deferred to the iterator in AbstractList, which check for concurrent modification - Warmup takes a bit longer due to having to warm up four different classes and associated methods - Slowdowns in certain code paths attributable to certain calls becoming megamorphic Microbenchmark: http://cr.openjdk.java.net/~redestad/scratch/less_immutables/ListMorphism.j… http://cr.openjdk.java.net/~redestad/scratch/less_immutables/benchmarks.jar The benchmark explores how call-sites behave when performing some naive operations on a few different Lists. For every benchmark using List.of() there's a variant using ArrayList for comparison: Baseline: Benchmark Mode Cnt Score Error Units ListMorphism.finalGetFromArrayList thrpt 25 92.659 ± 3.058 ops/us ListMorphism.finalGetFromList thrpt 25 335.245 ± 0.244 ops/us # 3.6x ListMorphism.finalSumSizesArrayList thrpt 25 245.020 ± 0.106 ops/us ListMorphism.finalSumSizesList thrpt 25 335.107 ± 0.439 ops/us # 1.4x ListMorphism.getFromArrayList thrpt 25 70.343 ± 0.972 ops/us ListMorphism.getFromList thrpt 25 37.121 ± 0.135 ops/us # 0.53x ListMorphism.getFromArrayList12 thrpt 25 109.890 ± 0.286 ops/us ListMorphism.getFromList12 thrpt 25 109.552 ± 6.972 ops/us # 1.0x ListMorphism.sumSizesArrayList thrpt 25 131.467 ± 4.672 ops/us ListMorphism.sumSizesList thrpt 25 57.877 ± 0.102 ops/us # 0.45x ListMorphism.sumSizesArrayList12 thrpt 25 208.652 ± 11.294 ops/us ListMorphism.sumSizesList12 thrpt 25 227.269 ± 0.961 ops/us # 1.1x The good: When dealing with List literals (the final* benchmarks), List.of() allows really nice speed-ups compared to ArrayList. The bad: When not used as a literal, List.of() implementations at call-sites can cause a substantial slowdown (megamorphic dispatch) The ugly: After some explorations[1], I narrowed in on the following experiment: http://cr.openjdk.java.net/~redestad/scratch/less_immutables/webrev/ Basically: Merge List1 and List2 into a single class, List12, merge List0 into ListN (List0 has a singleton instance, so might as well be an instance of ListN). Same for Set0,1,2,N. Map0 is merged into MapN. This strikes a balance between throughput, footprint and slightly better startup/warmup behavior. According to jol estimates[2] the size of List12 is the same as both List1 and List2 in the current JDK implementation. Set12 is footprint neutral compared to Set2 on all platforms but lose a few bytes on 64-bit VMs compared to Set1. Benchmark Mode Cnt Score Error Units ListMorphism.finalGetFromArrayList thrpt 25 93.046 ± 0.569 ops/us ListMorphism.finalGetFromList thrpt 25 335.280 ± 0.154 ops/us # 3.6x ListMorphism.finalSumSizesArrayList thrpt 25 244.595 ± 1.085 ops/us ListMorphism.finalSumSizesList thrpt 25 303.351 ± 0.182 ops/us # 1.2x ListMorphism.getFromArrayList thrpt 25 70.631 ± 0.070 ops/us ListMorphism.getFromList thrpt 25 73.258 ± 2.955 ops/us # 1.04x ListMorphism.getFromArrayList12 thrpt 25 109.921 ± 0.096 ops/us ListMorphism.getFromList12 thrpt 25 127.392 ± 0.088 ops/us # 1.16x ListMorphism.sumSizesArrayList thrpt 25 131.393 ± 4.882 ops/us ListMorphism.sumSizesList thrpt 25 107.686 ± 5.286 ops/us # 0.82x ListMorphism.sumSizesArrayList12 thrpt 25 212.350 ± 0.134 ops/us ListMorphism.sumSizesList12 thrpt 25 198.778 ± 0.479 ops/us # 0.94x The experiment has a flag to change number of specialized List/Set/Map classes (-Djdk.ImmutableCollections.specializations=0|1|2, default=2). 1 specialization (List1 + ListN, Set1 + SetN) is more or less the same as 2, some ~1-2% improvements, mainly in sumSizes micros. 0 specializations (List-, Set, MapN only) achieves a small increase in throughput on some micros by ensuring callsites stay monomorphic, but it's not very substantial by my measures (~5%, but mostly in sumSizes micros). Keeping the footprint more or less the same, while evening out a few rough edges and improving startup and static footprint seems like the overall best option. An alternative would be to keep the experimental flag, but I don't think a 5% gain on micros warrants the extra maintenance burden and testing that entails. The proposed patch is more or less this experiment with 2 specializations, but having removed the flag and code movement needed to support it removed (along with a fix in the writeReplace methods of List12/Set12) Thanks! /Claes [1] Older experiments: http://cr.openjdk.java.net/~redestad/immutable/list12N.0/ -- simply merge L0 into LN (still have L1, L2 and LN) - nothing really changed, though http://cr.openjdk.java.net/~redestad/immutable/list1N.0/ -- L0 merged into LN, drop L2. Substantial performance boost on micros. Footprint drop for 2-element lists. http://cr.openjdk.java.net/~redestad/immutable/listNdouble.0/ -- L0+L1+L2+LN merged into one implementation. Same footprint with a single class, but loses a lot on throughput in micros. http://cr.openjdk.java.net/~redestad/immutable/listNsingle.0/ -- L0+L1+LN merged, drop L2. Simplification of the previous. Like the list1N.0 experiment in footprint, but a loss in throughput on all measures. No approach seemed a win across the board here: we either had to accept a footprint reduction, or see throughput suffer dramatically. [2] http://openjdk.java.net/projects/code-tools/jol/

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RFR of 8180451: ByteArrayInputStream should override readAllBytes, readNBytes, and transferTo
by Brian Burkhalter 23 Mar '18

23 Mar '18

https://bugs.openjdk.java.net/browse/JDK-8180451 http://cr.openjdk.java.net/~bpb/8180451/webrev.00 1. Add overrides of readAllBytes(), readNBytes(), and transferTo(). 2. Simplify parameter checks in read(byte[],int,int). 3. Change <code>foo</code> to {@code foo}. Thanks, Brian

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Re: RFR 8181594: Efficient and constant-time modular arithmetic
by Adam Petcher 20 Mar '18

20 Mar '18

+core-libs-dev On 1/26/2018 4:06 PM, Adam Petcher wrote: > JBS: https://bugs.openjdk.java.net/browse/JDK-8181594 > Webrev: http://cr.openjdk.java.net/~apetcher/8181594/webrev.00/ > > This is a code review for the field arithmetic that will be used in > implementations of X25519/X448 key agreement, the Poly1305 > authenticator, and EdDSA signatures. I believe that the library has > all the features necessary for X25519/X448 and Poly1305, and I expect > at most a couple of minor enhancements will be required to support > EdDSA. There is no public API for this library, so we can change it in > the future to suit the needs of new algorithms without breaking > compatibility with external code. Still, I made an attempt to clearly > structure and document the (internal) API, and I want to make sure it > is understandable and easy to use. > > This is not a general-purpose modular arithmetic library. It will only > work well in circumstances where the sequence of operations is > restricted, and where the prime that defines the field has some useful > structure. Moreover, each new field will require some field-specific > code that takes into account the structure of the prime and the way > the field is used in the application. The initial implementation > includes a field for Poly1305 and the fields for X25519/X448 which > should also work for EdDSA. > > The benefits of using this library are that it is much more efficient > than using similar operations in BigInteger. Also, many operations are > branch-free, making them suitable for use in a side-channel resistant > implementation that does not branch on secrets. > > To provide some context, I have attached a code snippet describing how > this library can be used. The snippet is the constant-time Montgomery > ladder from my X25519/X448 implementation, which I expect to be out > for review soon. X25519/X448 only uses standard arithmetic operations, > and the more unusual features (e.g. add modulo a power of 2) are > needed by Poly1305. > > The field arithmetic (for all fields) is implemented using a 32-bit > representation similar to the one described in the Ed448 paper[1] (in > the "Implementation on 32-bit platforms" section). Though my > implementation uses signed limbs, and grade-school multiplication > instead of Karatsuba. The argument for correctness is essentially the > same for all three fields: the magnitude of each 64-bit limb is at > most 2^(k-1) after reduction, except for the last limb which may have > a magnitude of up to 2^k. The values of k are between 26 to 28 > (depending on the field), and we can calculate that the maximum > magnitude for any limb during an add-multiply-carry-reduce sequence is > always less than 2^63. Therefore, no overflow occurs and all > operations are correct. > > Process note: this enhancement is part of JEP 324 (Key Agreement with > Curve25519 and Curve448). When this code review is complete, nothing > will happen until all other work for this JEP is complete, and the JEP > is accepted as part of some release. This means that this code will be > pushed to the repo along with the X25519/X448 code that uses it. > > [1] https://eprint.iacr.org/2015/625.pdf > > >

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Re: [PATCH] Reduce Chance Of Mistakenly Early Backing Memory Cleanup
by Ben Walsh 12 Mar '18

12 Mar '18

Hi Paul, Following up with the requested loop and vectorization benchmarks ... (Do the vectorization benchmark results imply that the Hotspot compiler has been unable to perform the vectorization optimisation due to the presence of the reachabilityFence ?) ----------------------------------------------------------------------------------------------------------------------- Loop Benchmarking ---- ------------ package org.sample; import org.openjdk.jmh.annotations.Benchmark; import org.openjdk.jmh.annotations.Level; import org.openjdk.jmh.annotations.Param; import org.openjdk.jmh.annotations.Scope; import org.openjdk.jmh.annotations.Setup; import org.openjdk.jmh.annotations.State; import java.nio.ByteBuffer; @State(Scope.Benchmark) public class ByteBufferBenchmark { @Param({"1", "10", "100", "1000", "10000"}) public int L; @State(Scope.Benchmark) public static class ByteBufferContainer { ByteBuffer bb; @Setup(Level.Invocation) public void initByteBuffer() { bb = ByteBuffer.allocateDirect(10000); } ByteBuffer getByteBuffer() { return bb; } } @Benchmark public ByteBuffer benchmark_byte_buffer_put(ByteBufferContainer bbC) { ByteBuffer bb = bbC.getByteBuffer(); for (int i = 0; i < L; i++) { bb.put((byte)i); } return bb; } } Without Changes Benchmark (L) Mode Cnt Score Error Units ByteBufferBenchmark.benchmark_byte_buffer_put 1 thrpt 200 29303145.752 ± 635979.750 ops/s ByteBufferBenchmark.benchmark_byte_buffer_put 10 thrpt 200 24260859.017 ± 528891.303 ops/s ByteBufferBenchmark.benchmark_byte_buffer_put 100 thrpt 200 8512366.637 ± 136615.070 ops/s ByteBufferBenchmark.benchmark_byte_buffer_put 1000 thrpt 200 1323756.037 ± 21485.369 ops/s ByteBufferBenchmark.benchmark_byte_buffer_put 10000 thrpt 200 145965.305 ± 1301.469 ops/s With Changes Benchmark (L) Mode Cnt Score Error Units Impact ByteBufferBenchmark.benchmark_byte_buffer_put 1 thrpt 200 28893540.122 ± 754554.747 ops/s -1.398% ByteBufferBenchmark.benchmark_byte_buffer_put 10 thrpt 200 15317696.355 ± 231621.608 ops/s -36.863% ByteBufferBenchmark.benchmark_byte_buffer_put 100 thrpt 200 2546599.578 ± 32136.873 ops/s -70.084% ByteBufferBenchmark.benchmark_byte_buffer_put 1000 thrpt 200 288832.514 ± 3854.522 ops/s -78.181% ByteBufferBenchmark.benchmark_byte_buffer_put 10000 thrpt 200 29747.386 ± 214.831 ops/s -79.620% ----------------------------------------------------------------------------------------------------------------------- Vectorization Benchmarking ------------- ------------ package org.sample; import org.openjdk.jmh.annotations.Benchmark; import org.openjdk.jmh.annotations.Level; import org.openjdk.jmh.annotations.Param; import org.openjdk.jmh.annotations.Scope; import org.openjdk.jmh.annotations.Setup; import org.openjdk.jmh.annotations.State; import java.nio.ByteBuffer; @State(Scope.Benchmark) public class ByteBufferBenchmark { @Param({"1", "10", "100", "1000", "10000"}) public int L; @State(Scope.Benchmark) public static class ByteBufferContainer { ByteBuffer bb; @Setup(Level.Invocation) public void initByteBuffer() { bb = ByteBuffer.allocateDirect(4 * 10000); for (int i = 0; i < 10000; i++) { bb.putInt(i); } } ByteBuffer getByteBuffer() { return bb; } } @Benchmark public int benchmark_byte_buffer_put(ByteBufferContainer bbC) { ByteBuffer bb = bbC.getByteBuffer(); bb.position(0); int sum = 0; for (int i = 0; i < L; i++) { sum += bb.getInt(); } return sum; } } Without Changes Benchmark (L) Mode Cnt Score Error Units ByteBufferBenchmark.benchmark_byte_buffer_put 1 thrpt 200 29677205.748 ± 544721.142 ops/s ByteBufferBenchmark.benchmark_byte_buffer_put 10 thrpt 200 18219951.454 ± 320724.793 ops/s ByteBufferBenchmark.benchmark_byte_buffer_put 100 thrpt 200 7767650.826 ± 121798.910 ops/s ByteBufferBenchmark.benchmark_byte_buffer_put 1000 thrpt 200 1646075.010 ± 9804.499 ops/s ByteBufferBenchmark.benchmark_byte_buffer_put 10000 thrpt 200 183489.418 ± 1355.967 ops/s With Changes Benchmark (L) Mode Cnt Score Error Units Impact ByteBufferBenchmark.benchmark_byte_buffer_put 1 thrpt 200 15230086.695 ± 390174.190 ops/s -48.681% ByteBufferBenchmark.benchmark_byte_buffer_put 10 thrpt 200 8126310.728 ± 123661.342 ops/s -55.399% ByteBufferBenchmark.benchmark_byte_buffer_put 100 thrpt 200 1582699.233 ± 7278.744 ops/s -79.624% ByteBufferBenchmark.benchmark_byte_buffer_put 1000 thrpt 200 179726.465 ± 802.333 ops/s -89.082% ByteBufferBenchmark.benchmark_byte_buffer_put 10000 thrpt 200 18327.049 ± 9.506 ops/s -90.012% NB : For reference - for this and previous benchmarking results ... "Without Changes" and "With Changes" - java -version ... openjdk version "10-internal" 2018-03-20 OpenJDK Runtime Environment (build 10-internal+0-adhoc.walshbp.jdk) OpenJDK 64-Bit Server VM (build 10-internal+0-adhoc.walshbp.jdk, mixed mode) ----------------------------------------------------------------------------------------------------------------------- Regards, Ben Walsh From: Ben Walsh/UK/IBM To: Paul Sandoz <paul.sandoz(a)oracle.com> Cc: core-libs-dev <core-libs-dev(a)openjdk.java.net> Date: 05/02/2018 16:47 Subject: Re: [PATCH] Reduce Chance Of Mistakenly Early Backing Memory Cleanup Running with the following test under the JMH benchmark framework (never used this before, so please do point out any issues with the test) ... ------------------------------------------------------------------------------------------------------------------- package org.sample; import org.openjdk.jmh.annotations.Benchmark; import org.openjdk.jmh.annotations.Level; import org.openjdk.jmh.annotations.Scope; import org.openjdk.jmh.annotations.Setup; import org.openjdk.jmh.annotations.State; import java.nio.ByteBuffer; public class ByteBufferBenchmark { @State(Scope.Benchmark) public static class ByteBufferContainer { ByteBuffer bb; @Setup(Level.Invocation) public void initByteBuffer() { bb = ByteBuffer.allocateDirect(1); } ByteBuffer getByteBuffer() { return bb; } } @Benchmark public void benchmark_byte_buffer_put(ByteBufferContainer bbC) { bbC.getByteBuffer().put((byte)42); } } ------------------------------------------------------------------------------------------------------------------- ... I get the following results with and without the changes ... [9walsbp@dolphin ~]$ ./build_with/jdk/bin/java -jar benchmarks.jar WARNING: An illegal reflective access operation has occurred WARNING: Illegal reflective access by org.openjdk.jmh.util.Utils (file:/home/9walsbp/benchmarks.jar) to field java.io.Console.cs WARNING: Please consider reporting this to the maintainers of org.openjdk.jmh.util.Utils WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations WARNING: All illegal access operations will be denied in a future release # JMH version: 1.20 # VM version: JDK 10-internal, VM 10-internal+0-adhoc.walshbp.jdk # VM invoker: /home/9walsbp/build_with/jdk/bin/java # VM options: <none> # Warmup: 20 iterations, 1 s each # Measurement: 20 iterations, 1 s each # Timeout: 10 min per iteration # Threads: 1 thread, will synchronize iterations # Benchmark mode: Throughput, ops/time # Benchmark: org.sample.ByteBufferBenchmark.benchmark_byte_buffer_put # Run progress: 0.00% complete, ETA 00:06:40 # Fork: 1 of 10 # Warmup Iteration 1: 28572294.700 ops/s # Warmup Iteration 2: 33102015.934 ops/s # Warmup Iteration 3: 32883031.968 ops/s # Warmup Iteration 4: 32875302.586 ops/s # Warmup Iteration 5: 33708018.941 ops/s # Warmup Iteration 6: 34107603.885 ops/s # Warmup Iteration 7: 31615123.362 ops/s # Warmup Iteration 8: 34306874.876 ops/s # Warmup Iteration 9: 32615070.232 ops/s # Warmup Iteration 10: 34268641.323 ops/s # Warmup Iteration 11: 32209257.766 ops/s # Warmup Iteration 12: 34111408.999 ops/s # Warmup Iteration 13: 33527360.187 ops/s # Warmup Iteration 14: 34331726.136 ops/s # Warmup Iteration 15: 34325119.218 ops/s # Warmup Iteration 16: 31562168.904 ops/s # Warmup Iteration 17: 33227878.358 ops/s # Warmup Iteration 18: 34151154.273 ops/s # Warmup Iteration 19: 29264381.793 ops/s # Warmup Iteration 20: 30308058.560 ops/s Iteration 1: 33502237.659 ops/s Iteration 2: 33591469.068 ops/s Iteration 3: 29330487.674 ops/s Iteration 4: 31401627.173 ops/s Iteration 5: 32346391.980 ops/s Iteration 6: 34106932.868 ops/s Iteration 7: 29961218.721 ops/s Iteration 8: 31166503.731 ops/s Iteration 9: 34180826.531 ops/s Iteration 10: 34436432.202 ops/s Iteration 11: 28003272.167 ops/s Iteration 12: 30947688.218 ops/s Iteration 13: 33727404.696 ops/s Iteration 14: 33794727.241 ops/s Iteration 15: 34089932.945 ops/s Iteration 16: 30229615.627 ops/s Iteration 17: 32747950.250 ops/s Iteration 18: 34195332.494 ops/s Iteration 19: 34225966.793 ops/s Iteration 20: 30253949.366 ops/s # Run progress: 10.00% complete, ETA 00:27:45 # Fork: 2 of 10 # Warmup Iteration 1: 28189458.524 ops/s # Warmup Iteration 2: 33385943.637 ops/s # Warmup Iteration 3: 31474459.740 ops/s # Warmup Iteration 4: 32994555.969 ops/s # Warmup Iteration 5: 33580210.619 ops/s # Warmup Iteration 6: 34030937.323 ops/s # Warmup Iteration 7: 31891882.950 ops/s # Warmup Iteration 8: 34277935.152 ops/s # Warmup Iteration 9: 31636968.061 ops/s # Warmup Iteration 10: 34376216.983 ops/s # Warmup Iteration 11: 31790184.297 ops/s # Warmup Iteration 12: 34069806.835 ops/s # Warmup Iteration 13: 31737398.413 ops/s # Warmup Iteration 14: 34450863.223 ops/s # Warmup Iteration 15: 34568522.458 ops/s # Warmup Iteration 16: 30029081.882 ops/s # Warmup Iteration 17: 32092783.620 ops/s # Warmup Iteration 18: 33063366.197 ops/s # Warmup Iteration 19: 27694130.000 ops/s # Warmup Iteration 20: 31264525.792 ops/s Iteration 1: 33330874.247 ops/s Iteration 2: 34150690.011 ops/s Iteration 3: 28497705.592 ops/s Iteration 4: 31877639.021 ops/s Iteration 5: 33367324.280 ops/s Iteration 6: 34472176.807 ops/s Iteration 7: 29032738.714 ops/s Iteration 8: 31544864.097 ops/s Iteration 9: 33752028.095 ops/s Iteration 10: 34473732.353 ops/s Iteration 11: 29982974.569 ops/s Iteration 12: 30603336.272 ops/s Iteration 13: 32481117.249 ops/s Iteration 14: 33393570.191 ops/s Iteration 15: 34358979.713 ops/s Iteration 16: 27617909.839 ops/s Iteration 17: 30833802.394 ops/s Iteration 18: 32004461.408 ops/s Iteration 19: 34074910.495 ops/s Iteration 20: 34346053.320 ops/s # 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Run complete. Total time: 00:27:27 Benchmark Mode Cnt Score Error Units ByteBufferBenchmark.benchmark_byte_buffer_put thrpt 200 33100911.857 ± 747461.951 ops/s [9walsbp@dolphin ~]$ ./build_without/jdk/bin/java -jar benchmarks.jar WARNING: An illegal reflective access operation has occurred WARNING: Illegal reflective access by org.openjdk.jmh.util.Utils (file:/home/9walsbp/benchmarks.jar) to field java.io.Console.cs WARNING: Please consider reporting this to the maintainers of org.openjdk.jmh.util.Utils WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations WARNING: All illegal access operations will be denied in a future release # JMH version: 1.20 # VM version: JDK 10-internal, VM 10-internal+0-adhoc.walshbp.jdk # VM invoker: /home/9walsbp/build_without/jdk/bin/java # VM options: <none> # Warmup: 20 iterations, 1 s each # Measurement: 20 iterations, 1 s each # Timeout: 10 min per iteration # Threads: 1 thread, will synchronize iterations # Benchmark mode: Throughput, ops/time # Benchmark: org.sample.ByteBufferBenchmark.benchmark_byte_buffer_put # Run progress: 0.00% complete, ETA 00:06:40 # Fork: 1 of 10 # Warmup Iteration 1: 29113219.200 ops/s # Warmup Iteration 2: 38390854.347 ops/s # Warmup Iteration 3: 37576196.805 ops/s # Warmup Iteration 4: 38517882.972 ops/s # Warmup Iteration 5: 38838678.528 ops/s # Warmup Iteration 6: 38722019.753 ops/s # Warmup Iteration 7: 30279515.339 ops/s # Warmup Iteration 8: 37301591.985 ops/s # Warmup Iteration 9: 38937014.242 ops/s # Warmup Iteration 10: 38446665.693 ops/s # Warmup Iteration 11: 35988668.446 ops/s # Warmup Iteration 12: 37681609.419 ops/s # Warmup Iteration 13: 38993187.956 ops/s # Warmup Iteration 14: 37414379.929 ops/s # Warmup Iteration 15: 38753712.247 ops/s # Warmup Iteration 16: 38753551.189 ops/s # Warmup Iteration 17: 33767765.399 ops/s # Warmup Iteration 18: 37450537.087 ops/s # Warmup Iteration 19: 39118737.402 ops/s # Warmup Iteration 20: 39031101.838 ops/s Iteration 1: 32912027.168 ops/s Iteration 2: 37597695.079 ops/s Iteration 3: 37116802.899 ops/s Iteration 4: 37425452.741 ops/s Iteration 5: 31759009.838 ops/s Iteration 6: 37428294.033 ops/s Iteration 7: 38607838.742 ops/s Iteration 8: 34858025.193 ops/s Iteration 9: 36273653.347 ops/s Iteration 10: 38886985.073 ops/s Iteration 11: 38684265.699 ops/s Iteration 12: 30418949.886 ops/s Iteration 13: 36510488.388 ops/s Iteration 14: 37732064.835 ops/s Iteration 15: 37907332.810 ops/s Iteration 16: 38640267.003 ops/s Iteration 17: 31545863.662 ops/s Iteration 18: 36326351.514 ops/s Iteration 19: 37504107.281 ops/s Iteration 20: 36925861.540 ops/s # 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Run complete. Total time: 00:27:51 Benchmark Mode Cnt Score Error Units ByteBufferBenchmark.benchmark_byte_buffer_put thrpt 200 35604933.518 ± 654975.515 ops/s ... So a performance degradation of roughly 7%. Regards, Ben Walsh From: Paul Sandoz <paul.sandoz(a)oracle.com> To: Ben Walsh <ben_walsh(a)uk.ibm.com> Cc: core-libs-dev <core-libs-dev(a)openjdk.java.net> Date: 01/02/2018 22:50 Subject: Re: [PATCH] Reduce Chance Of Mistakenly Early Backing Memory Cleanup Hi Ben, I don?t think you require the fence in all the cases you have currently placed it e.g. here for example $memtype$ y = $toBits$(x); UNSAFE.put$Memtype$Unaligned(null, a, y, bigEndian); + Reference.reachabilityFence(this); return this; since ?this? is being returned it will be kept live during the unsafe access. Would you mind providing a JMH benchmark and results for the performance with and without the fence for say a put and/or a get. I would like to understand the performance impact on HotSpot, this is one reason why we have yet to add such fences as it will likely impact performance. At the moment we are relying on the method not being inlined, which is an expedient technique to make it functional and keep a reference alive but not necessarily optimal for usages in DBB. For more details see: https://bugs.openjdk.java.net/browse/JDK-8169605 https://bugs.openjdk.java.net/browse/JDK-8149610 Thanks, Paul. On Feb 1, 2018, at 6:55 AM, Ben Walsh <ben_walsh(a)uk.ibm.com> wrote: This contribution forms a partial solution to the problem detailed here - http://thevirtualmachinist.blogspot.ca/2011/07/subtle-issue-of-reachability… . In this context, this contribution provides "markers" such that a suitably "aware" compiler can reduce the chances of such a problem occurring with each of the Direct<Type>Buffer<RW><BO> objects and MappedByteBuffer object. The reachabilityFences may prevent crashes / exceptions due to cleaning up the backing memory before the user has finished using the pointer. Any compiler not suitably "aware" could be modified to make use of the "markers". I would like to pair with a sponsor to contribute this patch ... ------------------------------------------------------------------------------------------------------------------- diff -r d51e64840b4f src/java.base/share/classes/java/nio/Direct-X-Buffer-bin.java.template --- a/src/java.base/share/classes/java/nio/Direct-X-Buffer-bin.java.template Wed Jan 31 12:04:53 2018 +0800 +++ b/src/java.base/share/classes/java/nio/Direct-X-Buffer-bin.java.template Thu Feb 01 11:30:10 2018 +0000 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it @@ -33,15 +33,21 @@ private $type$ get$Type$(long a) { $memtype$ x = UNSAFE.get$Memtype$Unaligned(null, a, bigEndian); - return $fromBits$(x); + $type$ y = $fromBits$(x); + Reference.reachabilityFence(this); + return y; } public $type$ get$Type$() { - return get$Type$(ix(nextGetIndex($BYTES_PER_VALUE$))); + $type$ y = get$Type$(ix(nextGetIndex($BYTES_PER_VALUE$))); + Reference.reachabilityFence(this); + return y; } public $type$ get$Type$(int i) { - return get$Type$(ix(checkIndex(i, $BYTES_PER_VALUE$))); + $type$ y = get$Type$(ix(checkIndex(i, $BYTES_PER_VALUE$))); + Reference.reachabilityFence(this); + return y; } #end[rw] @@ -50,6 +56,7 @@ #if[rw] $memtype$ y = $toBits$(x); UNSAFE.put$Memtype$Unaligned(null, a, y, bigEndian); + Reference.reachabilityFence(this); return this; #else[rw] throw new ReadOnlyBufferException(); diff -r d51e64840b4f src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template --- a/src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template Wed Jan 31 12:04:53 2018 +0800 +++ b/src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template Thu Feb 01 11:30:10 2018 +0000 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it @@ -28,6 +28,7 @@ package java.nio; import java.io.FileDescriptor; +import java.lang.ref.Reference; import jdk.internal.misc.VM; import jdk.internal.ref.Cleaner; import sun.nio.ch.DirectBuffer; @@ -312,6 +313,7 @@ public $Type$Buffer put($type$ x) { #if[rw] UNSAFE.put$Swaptype$(ix(nextPutIndex()), $swap$($toBits$(x))); + Reference.reachabilityFence(this); return this; #else[rw] throw new ReadOnlyBufferException(); @@ -321,6 +323,7 @@ public $Type$Buffer put(int i, $type$ x) { #if[rw] UNSAFE.put$Swaptype$(ix(checkIndex(i)), $swap$($toBits$(x))); + Reference.reachabilityFence(this); return this; #else[rw] throw new ReadOnlyBufferException(); @@ -347,6 +350,7 @@ if (srem > rem) throw new BufferOverflowException(); UNSAFE.copyMemory(sb.ix(spos), ix(pos), (long)srem << $LG_BYTES_PER_VALUE$); + Reference.reachabilityFence(this); sb.position(spos + srem); position(pos + srem); } else if (src.hb != null) { @@ -413,6 +417,7 @@ int rem = (pos <= lim ? lim - pos : 0); UNSAFE.copyMemory(ix(pos), ix(0), (long)rem << $LG_BYTES_PER_VALUE$); + Reference.reachabilityFence(this); position(rem); limit(capacity()); discardMark(); @@ -505,6 +510,7 @@ void _put(int i, byte b) { // package-private #if[rw] UNSAFE.putByte(address + i, b); + Reference.reachabilityFence(this); #else[rw] throw new ReadOnlyBufferException(); #end[rw] diff -r d51e64840b4f src/java.base/share/classes/java/nio/MappedByteBuffer.java --- a/src/java.base/share/classes/java/nio/MappedByteBuffer.java Wed Jan 31 12:04:53 2018 +0800 +++ b/src/java.base/share/classes/java/nio/MappedByteBuffer.java Thu Feb 01 11:30:10 2018 +0000 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it @@ -26,6 +26,7 @@ package java.nio; import java.io.FileDescriptor; +import java.lang.ref.Reference; import jdk.internal.misc.Unsafe; @@ -164,6 +165,7 @@ // is computed as we go along to prevent the compiler from otherwise // considering the loop as dead code. Unsafe unsafe = Unsafe.getUnsafe(); + Reference.reachabilityFence(this); int ps = Bits.pageSize(); int count = Bits.pageCount(length); long a = mappingAddress(offset); ------------------------------------------------------------------------------------------------------------------- Regards, Ben Walsh Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU

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