<br><br><div class="gmail_quote">On Wed, Aug 10, 2011 at 12:56 PM, Mulyadi Santosa <span dir="ltr"><<a href="mailto:mulyadi.santosa@gmail.com">mulyadi.santosa@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Hi///<br>
<div class="im"><br>
On 09/08/2011, =/_00/\/\ <<a href="mailto:z0032oom@gmail.com">z0032oom@gmail.com</a>> wrote:<br>
> Hi,<br>
><br>
</div><div class="im">> Thanks for replying<br>
> Here is one observation worth mentioning.<br>
> On boot system it shows Mapped < Cached (In fact much less)<br>
<br>
</div>quite predictable.... during booting phase, your system read() much by<br>
doesn't mmap() that much....<br>
<div class="im"><br>
> After using system for some time following commands are executed.<br>
> # sync and echo 3 > /proc/sys/vm/drop_cache<br>
><br>
> Whenever above command is executed I can see Mapped > Cached.<br>
<br>
</div>by echoing "3" to drop_cache, you flush the content of page cache as<br>
much as possible ...<br>
<div class="im"><br></div></blockquote><div> </div><div>Here is my understanding of what drop_page_cache does:</div><div>All page-cache pages are 'dropped' except the following:</div><div>1. Dirty pages. (they are *not* synced)</div>
<div>2. Mapped pages (pages 'in use' , mapped by rmap )</div><div>(There are a few more exceptions i dont recall now.)</div><div><br></div><div>Hence even after dropping caches, free will still show some cached pages. These are dirty+mapped. </div>
<div>Doing a sync before dropping will only show the mapped pages. </div><div><br></div><div><br></div></div>