title: Intellij IDEA cursor navigation in editor lags
body: <p>After running IDEA for a few hours I've noticed that navigation starts to lag in the Editor. When I type something in it takes about 1-2 seconds to unfreeze the cursor. When I open a new line it also freezes for a while (pressing enter 5 times would freeze IDEA for around 10 seconds, if I wait every time until it unfreezes), as well as in similar situations. It feels that it is doing some sort of search (maybe index search) in background when the cursor freezes. Currently jvm heap shows at 292MB out of 674MB.</p>
  
  <p>What such problems can be related to and how to troubleshoot them?</p>
  
  <p>[UPDATE]</p>
  
  <p>Also <code>OutOfMemory</code> exception is thrown.</p>
  
  <pre><code>at com.intellij.util.io.PersistentEnumerator.enumerateImpl(PersistentEnumerator.java:354)
  at com.intellij.util.io.PersistentEnumerator.tryEnumerate(PersistentEnumerator.java:175)
  at com.intellij.util.io.PersistentHashMap.get(PersistentHashMap.java:219)
  at com.intellij.util.indexing.MapIndexStorage$1$1.compute(MapIndexStorage.java:78)
  at com.intellij.util.indexing.MapIndexStorage$1$1.compute(MapIndexStorage.java:70)
  
  Caused by: java.lang.RuntimeException: Mapping failed: C:\Users\...\Application Data\.IntelliJIdea90\system\index\idindex\IdIndex, position=0, length=10485760 
  
  at com.intellij.util.io.ReadWriteMappedBufferWrapper.map(ReadWriteMappedBufferWrapper.java:51)
  at com.intellij.util.io.MappedBufferWrapper.buf(MappedBufferWrapper.java:68)
  at com.intellij.util.io.PagedFileStorage.getBuffer(PagedFileStorage.java:260)
  at com.intellij.util.io.PagedFileStorage.get(PagedFileStorage.java:170)
  at com.intellij.util.io.PagedFileStorage.getInt(PagedFileStorage.java:121)
  at com.intellij.util.io.ResizeableMappedFile.getInt(ResizeableMappedFile.java:141)
  at com.intellij.util.io.PersistentEnumerator.enumerateImpl(PersistentEnumerator.java:279)
  ... 39 more
  Caused by: java.io.IOException: Map failed
  at sun.nio.ch.FileChannelImpl.map(FileChannelImpl.java:748)
  at com.intellij.util.io.ReadWriteMappedBufferWrapper.map(ReadWriteMappedBufferWrapper.java:48)
  ... 45 more
  Caused by: java.lang.OutOfMemoryError: Map failed
  at sun.nio.ch.FileChannelImpl.map0(Native Method)
  at sun.nio.ch.FileChannelImpl.map(FileChannelImpl.java:745)
  ... 46 more
  </code></pre>
  
  <p>[UPDATE II]</p>
  
  <p>Note that in Windows Task Manager memory usage is shown at nearly 1GB (which doesn't match suggested 292MB). Intellij built-in memory dump has produced a 500MB file. WTM shown memory in Intellij has gone down to 500MB as well (but it is still slow).</p>