Added -XX:[+|-]FlightRecorder` option - JFR #1471
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Sreekala-Gopakumar
added this to the Release 0.49 (Java 8, 11, 17, 21, 23) Jan refresh milestone
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docs/xxflightrecorder.md
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| `filename=...` specifies the name of the file where the recording must be saved. This parameter is optional. |
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What is the filename if filename= isn't specified?
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it uses the default defaultJ9recording.jfr file name
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Do we have to specify any directory location of this default file?
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The default file will be created in the process working directory
docs/xxflightrecorder.md
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| `filename=...` specifies the name of the file where the recording must be saved. This parameter is optional. | ||
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| `duration=..` specifies the duration of the recording. Units are seconds (s), minutes (m), hours (h), and days (d). This parameter is optional.  |
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What is the duration if duration= isn't specified?
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@tajila - Will it continue to record until the recording is manually stopped or the VM is shut down? Thanks!
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@tajila - Will it continue to record until the recording is manually stopped or the VM is shut down? Thanks!
Yes, this is the case
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| * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0 OR GPL-2.0-only WITH OpenJDK-assembly-exception-1.0 | ||
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I think we should add somewhere that this is a tech preview and all options may change in a future release
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What do you mean by "all options may change"? Which other options? Here we are only discussing the -XXFlightRecorder option, isn't it?
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Sorry, I should be more specific. The jcmd options may change
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Can we say "... JFR related jcmd options might change"?
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| `filename=...` specifies the name of the file where the recording must be saved. This parameter is optional. If a file name is not specified, the recording is saved in the `defaultJ9recording.jfr` file in the process working directory by default. | ||
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| `duration=..` specifies the duration of the recording. Units are seconds (s), minutes (m), hours (h), and days (d). This parameter is optional. If the duration is not specified, the tool continues to record until the recording is manually stopped or the VM is shut down.  |
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I think we should have an example. Can you specify, for example, both hours and minutes, how is this done? 1h30m?
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@tajila - Could you please provide an example of JFR jcmd command with both these parameters? Thanks!
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It only accepts 1 unit of time. Ie 12m, 1h, 54s or 2d
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eclipse-openj9#1469 New `-XX:[+|-]FlightRecorder` option and other related topics updated. Reviews comments incorporated. Closes eclipse-openj9#1469 Signed-off-by: Sreekala Gopakumar [email protected]
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@tajila @pshipton - I have made some changes based on the assumption that
We use < > to specify the parameter values in a command not [ ]. So for consistency's sake I have changed it. Please check and let me know if the changes are ok. Thanks! |
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It should be The |
| To start a recording, specify the following command: | ||
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| jcmd <JDK_ID> JFR.start filename=<file_name_with_path> duration=<time_with_unit_of_time> |
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To be consistent with https://eclipse.dev/openj9/docs/tool_jcmd/#java-diagnostic-command-jcmd-tool, it should be <vmid | display name | 0> rather than <JDK_ID>.
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| - `filename=<file_name_with_path>` specifies the name of the file and its location where the recording must be saved. The file name should have a `.jfr` extension. This parameter is optional. If a file name is not specified, the recording is saved in the `defaultJ9recording.jfr` file in the process working directory by default. |
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I suggest "where the recording is saved" rather than "must be saved".
#1469
New
-XX:[+|-]FlightRecorderoption and other related topics updated.Closes #1469
Signed-off-by: Sreekala Gopakumar [email protected]