Re: Drop caches - is this safe behavior?

[Dave Kleikamp <shaggy@linux.vnet.ibm.com>]

On Thu, 2007-08-23 at 21:36 -0400, Chris Snook wrote:

> If you think the system is doing the wrong thing (and it doesn't sound 
> like it is) you should be tweaking the vm.swappiness sysctl.  The 
> default is 60, but lower values will make it behave more like you think 
> it should be behaving, though you'll still probably see a tiny bit of 
> swap usage.  Of course, if your webservers are primarily serving up 
> static content, you'll want a higher value, since swapping anonymous 
> memory will leave more free for the pagecache you're primarily working with.

swappiness deals with page cache, whereas writing "2" to drop_caches
cleans out the inode and dentry caches.  Mike may be better off writing
a high number (say 10000) to /proc/sys/vm/vfs_cache_pressure.  This
would cause inode and dentry cache to be reclaimed sooner than other
memory.

-- 
David Kleikamp
IBM Linux Technology Center

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