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