title: linux kernel buffer memory is zero
body: <p>There are one qestion that i can`t find in google. </p>
  
  <p>I have many linux boxes mostly with SLES or openSUSE, diffrent versions and kernels.
  On some of them i faced with slow oracle transactions problem. It time to time problem and when i log in the box on that time i see that oracle blocked in kernel function sync_page</p>
  
  <pre><code># while :; do ps axo stat,pid,cmd,wchan | egrep '^D|^R'; echo --; sleep 5; done
  D     3483 hald-addon-storage: polling ide_do_drive_cmd
  Ds    4635 ora_dbw0_orcl               sync_page
  Ds    4637 ora_lgwr_orcl               sync_page
  Ds    4639 ora_ckpt_orcl               sync_page
  D    11210 oracleorcl (LOCAL=NO)       sync_page
  D    12457 [smtpd]                     sync_page
  R+   12458 ps axo stat,pid,cmd,wchan   -
  --
  Ds    4635 ora_dbw0_orcl               sync_page
  Ds    4637 ora_lgwr_orcl               sync_page
  Ds    4639 ora_ckpt_orcl               sync_page
  D    11210 oracleorcl (LOCAL=NO)       sync_page
  R+   12501 ps axo stat,pid,cmd,wchan   -
  --
  Ds    4635 ora_dbw0_orcl               sync_page
  Ds    4637 ora_lgwr_orcl               sync_page
  Ds    4639 ora_ckpt_orcl               sync_page
  D    11210 oracleorcl (LOCAL=NO)       sync_page
  R+   12535 ps axo stat,pid,cmd,wchan   -
  --
  Ds    4635 ora_dbw0_orcl               sync_page
  Ds    4637 ora_lgwr_orcl               sync_page
  Ds    4639 ora_ckpt_orcl               sync_page
  D    11210 oracleorcl (LOCAL=NO)       sync_page
  R+   12570 ps axo stat,pid,cmd,wchan   -
  --
  </code></pre>
  
  <p>so i think that box is run out of memory for disk buffers but</p>
  
  <pre><code>             total       used       free     shared    buffers     cached
  Mem:       4149084    3994552     154532          0          0    2424328
  -/+ buffers/cache:    1570224    2578860
  Swap:      3148700     750696    2398004
  </code></pre>
  
  <p>i think that this is the problem, buffer is zero and we must write directly to disk, but why buffer is zero - i try to google it and find nothing - is anyone can help ?</p>
  
  <p><strong>UPD</strong></p>
  
  <pre><code>billing@Billing-server:~&gt; uname -a
  Linux Billing-server 2.6.18.2-34-bigsmp #1 SMP Mon Nov 27 11:46:27 UTC 2006 i686 i686 i386 GNU/Linux
  </code></pre>