RFR 8080640: Reduce copying when reading JAR/ZIP entries (original) (raw)

Staffan Friberg staffan.friberg at oracle.com
Fri May 22 18:41:38 UTC 2015

On 05/21/2015 11:00 AM, Staffan Friberg wrote:

On 05/21/2015 09:48 AM, Staffan Friberg wrote:

On 05/20/2015 10:57 AM, Xueming Shen wrote: On 05/18/2015 06:44 PM, Staffan Friberg wrote: Hi,

Wanted to get reviews and feedback on this performance improvement for reading from JAR/ZIP files during classloading by reducing unnecessary copying and reading the entry in one go instead of in small portions. This shows a significant improvement when reading a single entry and for a large application with 10k classes and 500+ JAR files it improved the startup time by 4%. For more details on the background and performance results please see the RFE entry. RFE - https://bugs.openjdk.java.net/browse/JDK-8080640 WEBREV - http://cr.openjdk.java.net/~sfriberg/JDK-8080640/webrev.0 Cheers, Staffan Hi Staffan, If I did not miss something here, from your use scenario it appears to me the only thing you really need here to help boost your performance is byte[] ZipFile.getAllBytes(ZipEntry ze); You are allocating a byte[] at use side and wrapping it with a ByteBuffer if the size is small enough, otherwise, you letting the ZipFile to allocate a big enough one for you. It does not look like you can re-use that byte[] (has to be wrapped by the ByteArrayInputStream and return), why do you need two different methods here? The logic would be much easier to simply let the ZipFile to allocate the needed buffer with appropriate size, fill the bytes and return, with a "OOME" if the entry size is bigger than 2g. The only thing we use from the input ze is its name, get the size/csize from the jzentry, I don't think jzentry.csize/size can be "unknown", they are from the "cen" table. If the real/final use of the bytes is to wrap it with a ByteArrayInputStream,why bother using ByteBuffer here? Shouldn't a direct byte[] with exactly the size of the entry server better. -Sherman Hi Sherman, Thanks for the comments. I agree, was starting out with bytebuffer because I was hoping to be able to cache things where the buffer was being used, but since the buffer is past along further I couldn't figure out a clean way to do it. Will rewrite it to simply just return a buffer, and only wrap it in the Resource class getByteBuffer. What would be your thought on updating the ZipFile.getInputStream to return ByteArrayInputStream for small entries? Currently I do that work outside in two places and moving it would potentially speed up others reading small entries as well. Thanks, Staffan Just realized that my use of ByteArrayInputStream would miss Jar verification if enabled so the way to go hear would be to add it if possible to the ZipFile.getInputStream. //Staffan Hi,

Here is an updated webrev which uses a byte[] directly and also uses ByteArrayInputStream in ZipFile for small entries below 128k.

http://cr.openjdk.java.net/~sfriberg/JDK-8080640/webrev.1

//Staffan

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