9 fold improvement using RAMDir over MMapDir is much more than I've seen (~30-40% maybe) in the past.
Can you explain how you are using Lucene? You may also want to try the CachingRAMDirectory patch on https://issues.apache.org/jira/browse/LUCENE-4123 Mike McCandless http://blog.mikemccandless.com On Sat, Jun 16, 2012 at 7:18 AM, Cheng <zhoucheng2...@gmail.com> wrote: > After a number of test, the performance of MMapDirectory is not even close > to that of RAMDirectory, in terms of speed. > > My application w/ the former can only deal with 10 tasks per round while it > could handle over 90 w/ RAMDirectory. > > I use the application in Linux. > > What can be the reasons? > > Thanks. > > > On Tue, Jun 5, 2012 at 7:53 AM, Uwe Schindler <u...@thetaphi.de> wrote: > >> This is managed by your operating system. In general OS kernels like Linux >> or Windows use all free memory to cache disk accesses. >> >> ----- >> Uwe Schindler >> H.-H.-Meier-Allee 63, D-28213 Bremen >> http://www.thetaphi.de >> eMail: u...@thetaphi.de >> >> >> > -----Original Message----- >> > From: Cheng [mailto:zhoucheng2...@gmail.com] >> > Sent: Monday, June 04, 2012 6:10 PM >> > To: java-user@lucene.apache.org >> > Subject: Re: RAMDirectory unexpectedly slows >> > >> > Can I control the size of ram given to either MMapDirectory or >> > ByteBufferDirectory? >> > >> > On Mon, Jun 4, 2012 at 11:42 PM, Uwe Schindler <u...@thetaphi.de> wrote: >> > >> > > Hi, >> > > >> > > If you are using MMapDirectory or this ByteBufferDirectory (which is >> > > similar to the first) the used RAM is outside JVM heap, it is in the >> > > FS cache of the OS kernel. Giving too much memory to the JVM penalizes >> > > the OS cache, so give only as much as the App needs. Lucene and the OS >> > > kernel will then utilize the remaining memory for caching. >> > > >> > > Please read docs of MMapDirectory and inform yourself about mmap in >> e.g. >> > > Wikipedia. >> > > >> > > Uwe >> > > -- >> > > Uwe Schindler >> > > H.-H.-Meier-Allee 63, 28213 Bremen >> > > http://www.thetaphi.de >> > > >> > > >> > > >> > > Cheng <zhoucheng2...@gmail.com> schrieb: >> > > >> > > Please shed more insight into the difference between JVM heap size and >> > > the memory size used by Lucene. >> > > >> > > What I am getting at is that no matter however much ram I give my >> > > apps, Lucene can't utilize it. Is that right? >> > > >> > > What about the ByteBufferDirectory? Can this specific directory >> > > utilize the 2GB memory I grant to the app? >> > > >> > > On Mon, Jun 4, 2012 at 10:58 PM, Jason Rutherglen < >> > > jason.rutherg...@gmail.com> wrote: >> > > >> > > > If you want the index to be stored completely in RAM, there is the >> > > > ByteBuffer directory [1]. Though I do not see the point in putting >> > > > an index in RAM, it will be cached in RAM regardless in the OS >> > > > system IO cache. >> > > > >> > > > 1. >> > > > >> > > https://github.com/elasticsearch/elasticsearch/blob/master/src/main/ja >> > > va/org/apache/lucene/store/bytebuffer/ByteBufferDirectory.java >> > > > >> > > > On Mon, Jun 4, 2012 at 10:55 AM, Cheng <zhoucheng2...@gmail.com> >> > wrote: >> > > > > My indexes are 500MB+. So it seems like that RAMDirectory is not >> > > > > good >> > > for >> > > > > that big a size. >> > > > > >> > > > > My challenge, on the other side, is that I need to update the >> > > > > indexes >> > > > very >> > > > > frequently. So, do you think MMapDirectory is the solution? >> > > > > >> > > > > Thanks. >> > > > > >> > > > > On Mon, Jun 4, 2012 at 10:30 PM, Jack Krupansky < >> > > j...@basetechnology.com >> > > > >wrote: >> > > > > >> > > > >> From the javadoc for RAMDirectory: >> > > > >> >> > > > >> "Warning: This class is not intended to work with huge indexes. >> > > > Everything >> > > > >> beyond several hundred megabytes will waste resources (GC >> > > > >> cycles), >> > > > because >> > > > >> it uses an internal buffer size of 1024 bytes, producing millions >> > > > >> of byte[1024] arrays. This class is optimized for small >> > > > >> memory-resident indexes. It also has bad concurrency on >> multithreaded >> > environments. >> > > > >> >> > > > >> It is recommended to materialize large indexes on disk and use >> > > > >> MMapDirectory, which is a high-performance directory >> > > > >> implementation >> > > > working >> > > > >> directly on the file system cache of the operating system, so >> > > > >> copying >> > > > data >> > > > >> to Java heap space is not useful." >> > > > >> >> > > > >> -- Jack Krupansky >> > > > >> >> > > > >> -----Original Message----- From: Cheng >> > > > >> Sent: Monday, June 04, 2012 10:08 AM >> > > > >> To: java-user@lucene.apache.org >> > > > >> Subject: RAMDirectory unexpectedly slows >> > > > >> >> > > > >> >> > > > >> Hi, >> > > > >> >> > > > >> My apps need to read from and write to some big indexes >> frequently. >> > > So I >> > > > >> use RAMDirectory instead of FSDirectory, and give JVM about 2GB >> > > > >> memory size. >> > > > >> >> > > > >> I notice that the speed of reading and writing unexpectedly slows >> > > > >> as >> > > the >> > > > >> size of the indexes increases. Since the usage of RAM is less >> > > > >> than >> > > 20%, >> > > > I >> > > > >> think by default the RAMDirectory doesn't take advantage of the >> > > memory I >> > > > >> assigned to JVM. >> > > > >> >> > > > >> What are the steps to improve the reading and writing speed of >> > > > >> RAMDirectory? >> > > > >> >> > > > >> Thanks! >> > > > >> Jeff >> > > > >> >> > > > >> >> > > >_____________________________________________ >> > > **_____________________________________________ >> > > **--------- >> > > > >> To unsubscribe, e-mail: >> > > > >> java-user-unsubscribe@lucene.**apache.org< >> > > > java-user-unsubscr...@lucene.apache.org> >> > > > >> For additional commands, e-mail: >> > > > >> java-user-help@lucene.apache.**org< >> > > > java-user-h...@lucene.apache.org> >> > > > >> >> > > > >> >> > > > >> > > >_____________________________________________ >> > > >> > > > To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org >> > > > For additional commands, e-mail: java-user-h...@lucene.apache.org >> > > > >> > > > >> > > >> > > >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org >> For additional commands, e-mail: java-user-h...@lucene.apache.org >> >> --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
