|[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]|
On 19 Aug 2008, at 12:09 AM, Gerriet M. Denkmann wrote:
If the volume is not a root volume, it may not proceed to the filesystem calls that actually create the hotfiles btree. See #2 below.
Hotfiles are only supported on the root filesystem. Other filesystems do not get hotfiles support.
Well, the clumpSize referred to in the Tech Note is actually the clump size that gets written to disk, so it's updated as part of the periodic sync that runs every X seconds to push stuff to disk. It uses the data from the cnode to tell it what to write out, however. That data is updated upon every read, regardless of whether the data came from disk or the buffer cache.
Files are added and removed to the hotfiles list as vnodes are reclaimed and recycled. When the file goes out of scope, it goes through a bunch of checks for the temperature, who its parent is, the current hotfiles stage, among other things. If it passes all of the checks it is added to the hotfiles list. There isn't a way to trigger update of the hotfiles btree from userland via signals.
The formula is basically as as described. bytes read / Total blocks used by the fork. The only difference is that instead of using the clump value on-disk, HFS uses the data from the in-core data structures. The data structures could be out of sync from the in memory values, though I'm not sure that that would describe the discrepancies. How are you obtaining the information above?
Hot files can be moved if they were previously quiescent and then activity occurs on that file causing a vnode to be created for it. This means that there is likely some file activity on it. If they are still deemed hot after activity is finished, then it will be re-added to the hot files area. Alternatively, the coldest entry will be evicted once the area becomes full.
_______________________________________________ Do not post admin requests to the list. They will be ignored. Filesystem-dev mailing list (email@hidden) Help/Unsubscribe/Update your Subscription: This email sent to email@hidden
|>.hotfiles.btree (From: "Gerriet M. Denkmann" <email@hidden>)|
Visit the Apple Store online or at retail locations.
Copyright © 2011 Apple Inc. All rights reserved.