lkml.org 
[lkml]   [2008]   [Oct]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: SLUB defrag pull request?
On Wed, 22 Oct 2008, Miklos Szeredi wrote:

> Why? The kmem_cache_free() doesn't touch the contents of the object,
> does it?

Because filesystem code may be running on other processors which may be
freeing the dentry.

>> Because the slab starts out with a series of objects left in a slab. It
>> needs to do build a list of objects etc in a way that is independent as
>> possible from the user of the slab page. It does that by locking the slab
>> page so that free operations stall until the reference has been
>> established. If it would not be shutting off frees then the objects could
>> vanish under us.
>
> It doesn't matter. All we care about is that the dentry is on the
> lru: it's cached but unused. Every other state (being created,
> active, being freed, freed) is uninteresting.

We cannot figure out that it is on the lru if we do not have a stable
reference to the object.

> Sure, and all that is possible without doing this messy 2 phase thing.
> Unless I'm still missing something obvious...

Obviously one cannot free or handle an object that may be concurrently
freed on another processor.



\
 
 \ /
  Last update: 2008-10-22 21:59    [W:0.104 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site