Java performance tuning guide: high performance Java. Last updated: 0. 7 February 2. This is a summary of Java performance tuning tips described on.
This page will be updated after publishing. Java performance tuning website. Optimizing your Java code requires an understanding of how the different elements in Java interact, and how it interacts with the operating system that is it running on. Optimize Jpeg Java, free optimize jpeg java software downloads, Page 3. This is a page about the elusive subject of program performance optimization. Before you proceed towards such lofty goals, you should examine your reasons for doing so. I have covered most of essential functionality in the framework. JMH profilers will be the subject. This article covers JMH 1. It takes care of all. JMH also contains built- in support. It generates target/benchmarks. They will let you get an insight in your microbencmarks, which could not be available using. All JDK updates up to Java 7u. Don't use Math. Context. UNLIMITED. for that reason - it is equivalent to no context at all. This means that this method now has a linear complexity compared to. The advantage of this change is a slightly smaller memory footprint of a. String (8 bytes less than before) and a guarantee to avoid memory leaks caused by. String. substring (see. String packing part 1: converting characters to bytes for. Java object memory layout). This method is currently not public and could be accessed without reflection. Hashing. string. Hash. String) call. This method is used by 7 JDK hash- based. Not applicable to Java 8. See this article for more details. It will allow you to save memory occupied by the duplicate strings without writing a single line of Java code. It is a part of G1 garbage collector, so. G1 collector: - XX: +Use. G1. GC - XX: +Use. String. Deduplication. String deduplication is an optional G1 phase. It depends on the current system load. You don't need to write code to use this feature. String objects, each of those occupying 2. The minimal age of processed strings is managed by. XX: String. Deduplication. Age. Threshold=3 JVM parameter (3 is the default value of this parameter). You should avoid using direct byte buffers. Byte. Buffer bulk. Unsafe (though Byte. Buffer methods are always a little slower). Do not call Byte. Buffer. put! Always use String. Java 7. You can easily gain 1. Pattern methods with. Use an ordinary long instead. Calendar is useful for all sorts of date calculations and i. I advice you to read this article in conjunction with a. Date, java. util. Calendar and java. Simple. Date. Format performance. This article was tested on Joda Time ver 2. In essence it means that. Joda Time release you are using. For affected years date operations performance in Joda. Gregorian. Calendar. The advantage. of Joda parsing is that constructing a parser - Date. Time. Formatter object is extremely cheap, unlike. Simple. Date. Format, so you don't have to cache parsers anymore. It makes them. fast for human datetime arithmetics/conversion. Nevertheless, if you are processing computer time (a. In some rare cases when you are building. String from its byte representation, do not forget about. Byte. Array. Output. Stream. to. String methods. Garbage collecting these copies may take a noticeable time if your application. Inefficient byte. Default size for. Generally it worth increasing any of these. Though, keeping a Buffered. Input. Stream. is still safe. It will greatly speed up file reading. You can also try chaining 2. LZ4. Block. Output. Stream- s with 3. M buffer size to get most out of LZ4. If you want an instance of a wrapper class. It will support. caching of most frequently used values. Never call wrapper classes constructors - they always return. Object, thus bypassing the caching support. If its quality. is sufficient for you, use it instead of CRC3. In any case, use Checksum interface. Adler. 32/CRC3. 2 logic. Shorter blocks will require a noticeable time to be spent. JNI calls. This is far more important. Never write a hash. Code method which returns a constant. If you are working with sets of strings, try to end up with. Bit. Sets, as described in this article. Performance of your code will greatly improve. Creating an exception is too. Parse such values manually for top performance. Logging framework will call to. String method on your object. There is a new codec in Java 8. Base. 64 and there is also one hidden from many eyes (from Java 6): javax. Datatype. Converter. Unfortunately, if you will need. Google Guava will allow you to decode 2. G of data at a time. MB in case of Mi. GBase. 64 / 7. 20. M in case of IHarder and Apache Commons). Unfortunately, Guava does not support. You need to be. careful and split read and write accesses to the outer map. Choose ISO- 8. 85. US- ASCII. As you have seen. This property is achieved. String. equals/equals. Ignore. Case. Most of other Java memory optimization. The main cause of wrapper types usage are. JDK collections, so consider using one of primitive type collection frameworks like. Trove. For example, prefer array- based structures like. Array. List/Array. Deque to. pointer based structures like Linked. List. Such. replacement requires adding a single letter to your code (letter 'T') and no other code changes except the. Such replacement will give you significant memory savings - see table below. Remove static qualifier only when you have to. It means that you are limited by the whole. Java 7 and 8. It is fixed. Approximate the number of distinct. Each string added to the pool will be available. JVM thus further improving the program memory consumption. The simple example in this. String. intern(). You should not. use String. Instead process. only fields with a limited number of possible distinct values (for example, states/provinces if processing addresses) - . CPU costs of String. A routine until the moment the heap will exceed 3. At this time you will be surprised to see that you application is behaving even worse than before : (. What has happened? JVM has switched to using 6. Xmx. 32. G, which means that your app memory footprint has momentarily increased by 1. The actual area. of . There is also guidelines for migrating your code from JDK to Trove. They allow to reduce code required for many common tasks. Migration. to primitive- based collections require a bit more work, but this work will be paid off by massive reduction. On the other hand. Gb - 1 bytes as a size of your array - you may allocate a long. It may be equal to 4 or 8 bytes depending. JVM settings and on the amount of memory you have given to your JVM. It is always 8 bytes for heaps. G, but for smaller heaps it is 4 bytes unless you will turn off - XX: -Use. Compressed. Oops. JVM setting. This will increase the compression. You will get a noticeable data size reduction at a very low CPU cost, which will help you. Often same information. Price. Unsigned. and 3f 8. Try to identify. cases when most of your data can fit into a more compact data type than an original one. Try to identify. cases when most of your data can fit into a more compact data type than an original one. Number- to- number maps. In this case. a map can be converted into the array. After that we try to pack a String into a more compact representation, trying. Objects. That's why they can share internal. They also cache the calculated hash code value, because strings are often. Hash. Map keys or Hash. Set values. But these properties add a great penalty. We can avoid this penalty by implementing our own string replacement objects. Unfortunately, it is not supported anymore in Java 7, maybe due. This is loseless conversion, so you could always convert your binary byte. Your write. requests will be blocked only if OS can't write data faster than your application produces it. On the other hand, even SSD seek is too slow compared to modern CPU speed. On my laptop, CPU. SSD executes a seek operation. Always try to arrange your data. Then we will see what's hidden in the array header and will. You can use sun. misc. Unsafe in. order to treat such references as int fields. Length (int). is stored at offset=1. Changing these values is possible, but care must be taken in order not to extend an updated. Such updates. to static final fields of primitive/String initialized with complile- time expressions will not be. JLS 1. 5. 2. 8) are inlined. You can use. Thread. Throwable), Class. Instance (and throw an exception in the constructor). Unsafe. throw. Exception or use generic type erasure in order to avoid a checked exception. We do not recommend you to use any of these practices : ). In Java you may create an object without calling any of its constructors. There are 2 legal ways to do it - . But there is a way to force it run in the compiled mode. Tags: Java pitfalls, avoid it. In this case try to move that logic into a separate helper class. Use appropriate. String. Of or wrapper types to. String(value) methods instead. Check old code and get rid of. String. Buffer is possible. It is turned on by default in most of Java 7 releases, but it is still turned off in Java 6. Part 1: Writing a simple FIX parser and. Use case: FIX messages processing. Part 2: Composing a message out of fields: possible gateway implementation. FIX message parsing and composing. In essence, we parse a 0x. In the second part we will discuss. String format as a part of a gateway implementation. The only exception is a single character pattern in Java 7. String. index. Of(char). Besides saving CPU cycles on data conversions, you will also. At least, limit the number of such files. The same applies to the case of one application. OS file cache instead of actually reading them from the disk. Dynamic dispatch. Groovy 2. 1. 9 is approximately 3 times slower compared to a normal Java method call due to the need to obtain. Method. Besides performance. Groovy code, letting you. We can check that a double variable contains an integer value if we will cast it to long. Both casts are cheap operations. If we have a double value, which is possibly one ulp off the actual result, we may try to multiply this. If not, try to add. Math. next. After to. If we will divide a long value by a double non- negative power of 1. Same applies to the case of division of a double containing. At the same time we can not replace. N by multiplication by 1. N: the result will be off by ulp in many cases. At the same time. N if we are allowed to round the result using Math.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
January 2017
Categories |