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Jayakrishnan Salim
Jayakrishnan Salim

Reputation: 987

What is the best size for a buffer in BlackBerry?

In my application I need to read data from an input stream. I have set the current buffer size for reading as 1024. But I have seen in some Android applications buffer size has been kept as 8192 (8 KB). Will there be any specific advantage if I increase the buffer size in my application to 8KB?

Any expert opinion will be much appreciated.

Edit: (I am using BB OS 6 and 7 and I am dealing with network inputstream.)

Upvotes: 1

Views: 176

Answers (2)

Peter Strange
Peter Strange

Reputation: 2650

This question was also asked in the official BlackBerry forum here:

http://supportforums.blackberry.com/t5/Java-Development/What-is-the-best-size-for-a-buffer-in-BlackBerry/td-p/2559417

The OP gave this clarification:

"I am reading from network. Once I establish socket connection with the server, the server will send me notifications one after the other. I need to read the notifications/data from the inputstream available in the socket connection. For this I have a background thread which checks anything is available in the inputstream and if something is available, it will read with the help of a buffer and then passes the read data to a StringBuffer."

Given this information, I have a different take, in that I think the BlackBerry network handling abstracts the Java application from the network buffer processing to the extent that the application buffer size will have little if any impact on the performance.

But be aware, this is only my opinion.

My response on that thread was as follows:

First thing to note is that the method "isAvailable()", in my experience, does not work correctly on OS 5.0 and earlier. It is fixed in OS 6 (at least from my testing).

Because isAvailable() was broken, (and for other application reasons) what I have implemented for a socket connection is that each message is preceded by a length. So in the socket connection, I read the length of the next message, and then the actual data. This is done with no blocking - in other words I read the entire message, regardless of size. I recommend you do the same. The message must exist in full somewhere so it makes no difference if it is in some memory managed by the socket connection, or in some memory managed by you.

Note also, until OS 6.0, when you did the read you would get all the data to fill the buffer you had - in other words it waited till the buffer was full. In OS 6.0 and later, the read can complete without giving you a full buffer.

In your case, you might be working in a post OS 6.0 only, so you could use isAvailable() - create a buffer of that size, and read everything. I can't see that it makes any difference whether you have the bytes in memory managed by the socket, or memory managed by you.

But in fact, I would argue that the best approach is the one that makes your processing simplest. So for example, if you know that the next message is 200 bytes, then read 200 bytes, and then process that message. Then read the next message.

You could spend a lot of time attempting to manage the buffers to match the underlying socket buffers. I don't know exactly how the underlying BlackBerry socket processing code works, but it doesn't put data directly into your buffers. So let it manage its buffer size to optimize the network, you manage your buffer size to optimize your processing. That will work best for everyone.

Upvotes: 1

Nate
Nate

Reputation: 31045

I can't say that I've found the universally best buffer size, but it seems to me that something in the range of 1KB to 8KB should be fine in most situations (for BlackBerry Java apps).

Keep in mind that if the amount of data is small (so you'd probably only need one or two buffers at 1KB-8KB), it's probably best just to use the IOUtilities method:

byte[] result = IOUtilities.streamToBytes(inputStream);

with which you don't need to actually pick a buffer size. But, if you know that result would be a large block of data, you're probably right in wanting to read one buffer at a time.

However, I would argue that the answer should almost always be obtained simply by building the app, and measuring performance with a few different values for byte buffer size. It's easy enough to change one constant, build, run and measure again, and then you're not guessing, or taking the advice of someone who doesn't know all the details of your app.

See here for information about BlackBerry Eclipse plugin memory analysis, and here for BlackBerry Eclipse plugin profiling.

These tools are found in Eclipse by selecting the Window menu, then Show View -> Other... -> BlackBerry -> BlackBerry Memory Statistics View, or BlackBerry Profiler View, while debugging.

This way, you can see how much memory, or processor, the network code is using during the call to retrieve data and populate your buffer.

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BlackBerry InputStream to String conversion

Upvotes: 2

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