title: I/O operations are blocking mysql transactions
body: <p>here we have a x64 Debian Lenny with MySQL 5.1.47 and some InnoDB databases on it. ibdata files and other stuff is on the same file system (ext3). I've noticed, that on some situations there are many processes in MySQL process list which hang on "freeing items" state. This happens when I do the following on shell (file1 and file2 are about 2.5gb)</p>
  
  <pre><code>cat file1 file2 &gt;new_file
  </code></pre>
  
  <p>or execute the following SQL statement</p>
  
  <pre><code>SELECT 'name' AS col UNION SELECT col FROM db_name.table_name INTO OUTFILE ('/var/xxx/yyy')
  </code></pre>
  
  <p>When one of these two things is running, then I can see many MySQL processes running endless with "freeing items" state (I'm using innotop). When killing this shell process (or SQL statement) then these blocked transactions disappear.</p>
  
  <p>In internet I found some hints to disable InnoDB adaptive hash index and common query cache, but this doesn't help. Is there someone who has the same experience?</p>
  
  <p>Regards</p>