On Sat, 20 Feb 2021 00:47:56 GMT, Hamlin Li <[email protected]> wrote:
>> BTW, we have three PRs related to `parallel=<n>`. I think it would be best
>> to hold off pushing any of them until they have all been reviewed and
>> approved. One reason is because the `parallel=<n>` output should be
>> consistent for all of them, and if there is a minor suggestion for a change
>> in one, it should be applied to all 3.
>
>> BTW, we have three PRs related to `parallel=<n>`. I think it would be best
>> to hold off pushing any of them until they have all been reviewed and
>> approved. One reason is because the `parallel=<n>` output should be
>> consistent for all of them, and if there is a minor suggestion for a change
>> in one, it should be applied to all 3.
>
> Sure, will hold off.
> Summarize the help messages as below:
> "Number of parallel threads to use for heap inspection. "
> "0: let the VM determine the number of threads to use. "
> "1: use one thread, i.e. disable parallelism. "
> "n: Request that threads be used. n must be positive. The VM will try to use
> n threads, but might use fewer threads than n."
For jmap -histo we have:
parallel=<number> parallel threads number for heap iteration:
parallel=0 default behavior, use predefined
number of threads
parallel=1 disable parallel heap iteration
parallel=<N> use N threads for parallel heap
iteration
It's a bit inconsistent here in that it says <number>, <N>, and N. I'd like to
see that cleaned up at some point along with a few other things (as part of a
separate PR). However, my point is that the value of the argument is given a
name, <number> in this case, so it can be referenced in the help output.
However, jmap help is done differently than jcmd help, which doesn't give names
to the value of options. For example, GC.heap_dump has:
Options: (options must be specified using the <key> or <key>=<value> syntax)
-all : [optional] Dump all objects, including unreachable objects
(BOOLEAN, false)
-gz : [optional] If specified, the heap dump is written in gzipped
format using the given compression level. 1 (recommended) is the fastest, 9 the
strongest compression. (INT, 1)
The -gz option is much like -parallel in that a value is given for it, but
there is no "name" for that value in the help output. So maybe we should avoid
calling it "n" or <n>, or anything like that:
"Number of parallel threads to use for heap inspection."
"0 (the default) means let the VM determine the number of threads to use. "
"1 means use one thread (disable parallelism). "
"For any other value the VM will try to use the specified number of threads,
but might use fewer."
I think we can leave out "Must be positive." It should be obvious, and I assume
an error is generated if negative number is given.
-------------
PR: https://git.openjdk.java.net/jdk/pull/2379
