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https://issues.apache.org/jira/browse/CASSANDRA-1214?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12896571#action_12896571
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Folke Behrens commented on CASSANDRA-1214:
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{quote}
How does the JNA approach behave if there is no C library (Windows?) or
mlockall doesn't exist (OS X?)
{quote}
In case of Mac OS X an UnsatisfiedLinkError will be thrown. Windows? I don't
know. Maybe a JNA-specific exception, maybe a ULE, too. OS's can be easily
detected with Platform.isXXX() and dealt with accordingly.
{quote}
something as simple as "grab errno" became a holy mess of portability concerns.
{quote}
Yes, but errno is a particularly hard case. The "inventors" messed up big time
with this. That's why the JNA developers provide two ways to check errno: you
either mark your methods with "throws LastErrorException" or you ask
Native.getLastError(). This works under Windows, too.
{quote}
The proposed JNA patch seems to suffer from exactly this problem as far as I
can see, making assumptions about what the concrete values are of MCL_CURRENT
and MCL_FUTURE.
{quote}
Theoretically, you're right, in practice, however, I can't find a single POSIX
system that assigns different values to MCL_CURRENT or MCL_FUTURE, and I think
it's highly unlikely that these will change in the future. If so, Cassandra's
code can be adjusted.
{quote}
As far as I can tell, once one has gotten over the initial one-time hurdle of
using JNI and the associated building issues, you have a much more
correct/standards-compliant access to the native platform than through JNA
since you're in compile time with access to appropriate headers etc.
Please do correct me if I'm wrong, since the idea of avoiding compile
time/build issues is certainly very attractive and the reason why I tried to
find an acceptable solution with JNA in the past.
{quote}
You're absolutely right, and your JNI code is really superb. If Cassandra needs
to bind a couple more native functions I'd say JNI is the way to go. But not
just yet.
> Make standard IO the default
> ----------------------------
>
> Key: CASSANDRA-1214
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1214
> Project: Cassandra
> Issue Type: Bug
> Reporter: James Golick
> Attachments: mlockall-jna.patch.txt, Read Throughput with mmap.jpg,
> trunk-1214.txt
>
>
> The way mmap()'d IO is handled in cassandra is dangerous. It allocates
> potentially massive buffers without any care for bounding the total size of
> the program's buffers. As the node's dataset grows, this *will* lead to
> swapping and instability.
> This is a dangerous and wrong default for a couple of reasons.
> 1) People are likely to test cassandra with the default settings. This issue
> is insidious because it only appears when you have sufficient data in a
> certain node, there is absolutely no way to control it, and it doesn't at all
> respect the memory limits that you give to the JVM.
> That can all be ascertained by reading the code, and people should certainly
> do their homework, but nevertheless, cassandra should ship with sane defaults
> that don't break down when you cross some magic unknown threshold.
> 2) It's deceptive. Unless you are extremely careful with capacity planning,
> you will get bit by this. Most people won't really be able to use this in
> production, so why get them excited about performance that they can't
> actually have?
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