Re: Drop caches - is this safe behavior?

[Chris Snook <csnook@redhat.com>]

Dave Kleikamp wrote:
> 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.
> 

Thanks, I was confusing this with dropping pagecache.

Mike --

	Try Dave's suggestion to increase vm.vfs_cache_pressure.  drop_pages 
should never be needed, regardless of which caches you're dropping.

	-- Chris

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>