Hi Daniel,
I'm not proposing to add any caching, or change anything about the Java side of
NetworkInterface, for exactly the reasons you state. This first patch is purely
a change to the native code to make it so that getAll only calls the Windows
API once instead of N + 1 times. createNetworkInterface actually already had
parameters for passing the previously fetched list of interfaces. getAll just
doesn't currently do that.
This would probably be easier to discuss if you could actually see the changes
I'm proposing. Should I attach a patch to an email, or is there a better way of
doing that?
Thanks,
Rich DiCroce
Senior Advanced Solutions Architect
Scientific Games
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-----Original Message-----
From: Daniel Fuchs <daniel.fu...@oracle.com>
Sent: Tuesday, February 7, 2023 3:52 PM
To: DiCroce, Richard <rich.dicr...@scientificgames.com>; net-dev@openjdk.org
Subject: Re: Performance of NetworkInterface methods on Windows
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unless you recognize the sender and know the content is safe.
Hi Richard,
Welcome to OpenJDK :-)
A NetworkInterface object has a state, of which a subset is a snapshot of some
information that was read and copied at the time the NetworkInterface object
was created. Typically, the list of addresses bound to the interface is a
snapshot.
Getting the entire NetworkInterface all over again ensures that the new
interface object has a new refreshed snapshot of this state. It may not be the
best implementation depending on what the calling code is trying to achieve,
but this is a long standing behavior (even though unspecified) that cannot be
changed without incurring high risk of regressions in existing applications.
I'm not sure what your patch is proposing to do - but I'm not sure it will be a
pure performance fix without any impact on observable behavior.
Naively caching interfaces created by a previous call would not work, for
instance.
There is certainly performance gains to be had, and making use of the new
foreign memory API to reduce the number of upcalls could be an avenue to
explore.
Backward compatibility is a concern to keep in mind though.
best regards,
-- daniel
PS: I see Alan has already replied on some other aspects
of your inquiry.
On 07/02/2023 20:06, DiCroce, Richard wrote:
> Hi everyone,
>
> I’d like to propose a patch to fix a performance issue with
> enumerating network interfaces on Windows. The problem stems from the
> fact that getAll calls createNetworkInterface for every interface, but
> does not pass the list of interfaces that it has already collected. As
> a result, createNetworkInterface gets the entire list all over again.
>
