8274113: (fc) Tune FileChannel.transferFrom() #8644

bplb · 2022-05-10T23:05:19Z

This request proposes to change FileChannel.transferFrom() to add a fast path on Linux and a threshold for mapped transfers on all platforms.

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Issue

JDK-8274113: (fc) Tune FileChannel.transferFrom()

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Alan Bateman (@AlanBateman - Reviewer)

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bplb · 2022-05-10T23:06:23Z

To transferFrom() a direct transfer path is added by the method transferFromDirectly() for the case where the source ReadableByteChannel is a FileChannel. If a native fast transfer function is available, then it will be used for the transfer between FileChannels. Currently the only such platform function is copy_file_range() on Linux. If no such function is available, this path will be attempted only once. This direct path was measured to improve throughput by from 25% to 300%.

A threshold is added for all platforms such that a mapped transfer is attempted only when the number of bytes to transfer is greater than the threshold. Below this threshold a read-write copy is performed.

The test Transfers.java is modified not to require that transferFrom() return a value equal to its count parameter which is not required by the specification:

Fewer than the requested number of bytes will be transferred [...]

Instead, transferFrom() is called in a loop until the cumulative number of bytes equals the expected value or an error occurs.

bridgekeeper · 2022-05-10T23:06:48Z

👋 Welcome back bpb! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2022-05-10T23:08:25Z

@bplb The following label will be automatically applied to this pull request:

nio

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mlbridge · 2022-05-10T23:12:19Z

Webrevs

src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java

src/java.base/unix/native/libnio/ch/FileChannelImpl.c

AlanBateman

Overall I think this looks good. It would be useful to add some performance data to the PR to demonstrate the improvement.

openjdk · 2022-05-11T13:08:43Z

@bplb This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8274113: (fc) Tune FileChannel.transferFrom()

Reviewed-by: alanb

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 80 new commits pushed to the master branch:

cc7560e: 8286287: Reading file as UTF-16 causes Error which "shouldn't happen"
82aa045: 8286015: JFR: Remove jfr.save.generated.asm
1904e9d: 8286423: Destroy password protection in the example code in KeyStore
e4439ca: 8284283: javac crashes when several transitive supertypes are missing
752ad1c: 8286422: Add OIDs for RC2 and Blowfish
36bdd25: 8286573: Remove the unnecessary method Attr#attribTopLevel and its usage
dea6e88: 8284680: sun.font.FontConfigManager.getFontConfig() leaks charset
40f43c6: 8286601: Mac Aarch: Excessive warnings to be ignored for build jdk
be97b4b: 8278348: [macos12] javax/swing/JTree/4908142/bug4908142.java fails in macos12
ff17f49: 8284888: [macos] javax/swing/JInternalFrame/8146321/JInternalFrameIconTest.java failed with "NimbusLookAndFeel] : ERROR: icon and imageIcon not same."
... and 70 more: https://git.openjdk.java.net/jdk/compare/97a983526b41d26fcd1caa162a089690119874b0...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

bplb · 2022-05-11T17:34:18Z

Overall I think this looks good. It would be useful to add some performance data to the PR to demonstrate the improvement.

Throughput on macOS showing the change due to the mapped transfer threshold:

Before (mapped transfer)

Benchmark                  (length)   Mode  Cnt      Score     Error  Units
TransferFrom.transferFrom      8000  thrpt   10  83171.694 ± 394.409  ops/s
TransferFrom.transferFrom     12000  thrpt   10  78985.812 ± 405.395  ops/s
TransferFrom.transferFrom     14000  thrpt   10  74194.782 ± 387.265  ops/s
TransferFrom.transferFrom     16000  thrpt   10  74117.711 ± 301.495  ops/s
TransferFrom.transferFrom     17000  thrpt   10  70074.672 ± 562.279  ops/s
TransferFrom.transferFrom     18000  thrpt   10  69862.113 ± 348.783  ops/s
TransferFrom.transferFrom     19000  thrpt   10  69742.800 ± 264.864  ops/s
TransferFrom.transferFrom     20000  thrpt   10  69017.441 ± 208.591  ops/s
TransferFrom.transferFrom     22000  thrpt   10  65326.088 ± 281.195  ops/s
TransferFrom.transferFrom     24000  thrpt   10  64996.134 ± 254.554  ops/s

After (read-write transfer up to 16K length)

Benchmark                  (length)   Mode  Cnt       Score      Error  Units
TransferFrom.transferFrom      8000  thrpt   10  178033.028 ± 1048.081  ops/s
TransferFrom.transferFrom     12000  thrpt   10   99595.963 ± 1044.993  ops/s
TransferFrom.transferFrom     14000  thrpt   10   97869.683 ±  548.820  ops/s
TransferFrom.transferFrom     16000  thrpt   10   94392.964 ±  827.057  ops/s
TransferFrom.transferFrom     17000  thrpt   10   67670.339 ±  735.683  ops/s
TransferFrom.transferFrom     18000  thrpt   10   68161.273 ±  384.360  ops/s
TransferFrom.transferFrom     19000  thrpt   10   68453.820 ±  632.199  ops/s
TransferFrom.transferFrom     20000  thrpt   10   68701.903 ± 1042.648  ops/s
TransferFrom.transferFrom     22000  thrpt   10   65713.451 ±  497.990  ops/s
TransferFrom.transferFrom     24000  thrpt   10   66525.251 ± 1017.672  ops/s

The threshold could probably be a little higher but is left at 16K for consistency with transferTo().

Throughput on Linux showing the change due to direct transfer:

Before (mapped transfer)

Benchmark                  (length)   Mode  Cnt      Score      Error  Units
TransferFrom.transferFrom     16384  thrpt    5  95885.876 ± 1153.982  ops/s
TransferFrom.transferFrom    131072  thrpt    5  30699.784 ±  653.334  ops/s
TransferFrom.transferFrom   1000000  thrpt    5   6840.268 ±  162.586  ops/s

After (copy_file_range())

Benchmark                  (length)   Mode  Cnt       Score      Error  Units
TransferFrom.transferFrom     16384  thrpt    5  236198.847 ± 2070.598  ops/s
TransferFrom.transferFrom    131072  thrpt    5   59197.335 ± 1596.413  ops/s
TransferFrom.transferFrom   1000000  thrpt    5    8135.444 ±  758.260  ops/s

src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java

bplb · 2022-05-12T18:49:28Z

/integrate

openjdk · 2022-05-12T18:50:12Z

Going to push as commit 986d87d.
Since your change was applied there have been 89 commits pushed to the master branch:

61cb4b7: 8285951: Replace Algorithms.eatMemory(...) with WB.fullGC() in vmTestbase_vm_gc_ref tests
5ff1d22: 8286386: Address possibly lossy conversions in java.net.http
7118343: 8278262: JFR: TestPrintXML can't handle missing timestamps
74eee28: 8286560: Remove user parameter from jdk.internal.perf.Perf.attach()
160944b: 8286615: Small refactor to SerializedLambda
17c5278: 8286378: Address possibly lossy conversions in java.base
0a6832b: 8286617: Improve parameter names in javax.lang.model utility visitors
2c5d136: 8282191: Implementation of Foreign Function & Memory API (Preview)
3be394e: 8275535: Retrying a failed authentication on multiple LDAP servers can lead to users blocked
cc7560e: 8286287: Reading file as UTF-16 causes Error which "shouldn't happen"
... and 79 more: https://git.openjdk.java.net/jdk/compare/97a983526b41d26fcd1caa162a089690119874b0...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-05-12T18:50:29Z

@bplb Pushed as commit 986d87d.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

openjdk bot added the rfr Pull request is ready for review label May 10, 2022

openjdk bot added the nio nio-dev@openjdk.org label May 10, 2022

8274113: (fc) Tune FileChannel.transferFrom()

df436ab

bplb force-pushed the FileChannel-transferFrom-8274113 branch from 4ea9b94 to df436ab Compare May 10, 2022 23:28

AlanBateman reviewed May 11, 2022

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src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java Outdated Show resolved Hide resolved

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8274113: Invert transferXXXSupported

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AlanBateman reviewed May 12, 2022

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src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java Outdated Show resolved Hide resolved

8274113: Remove volatile write of false to transferXXXNotSupported

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AlanBateman approved these changes May 12, 2022

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openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels May 12, 2022

bplb deleted the FileChannel-transferFrom-8274113 branch May 12, 2022 19:01

bplb mentioned this pull request May 16, 2022

8286763: [REDO] (fc) Tune FileChannel.transferFrom() #8733

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