Re: [PATCH v9 05/13] memcg: add mem_cgroup_mark_inode_dirty()

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Wed, 17 Aug 2011 09:14:57 -0700
Greg Thelen <gthelen@google.com> wrote:

> Create the mem_cgroup_mark_inode_dirty() routine, which is called when
> an inode is marked dirty.  In kernels without memcg, this is an inline
> no-op.
> 
> Add i_memcg field to struct address_space.  When an inode is marked
> dirty with mem_cgroup_mark_inode_dirty(), the css_id of current memcg is
> recorded in i_memcg.  Per-memcg writeback (introduced in a latter
> change) uses this field to isolate inodes associated with a particular
> memcg.
> 
> The type of i_memcg is an 'unsigned short' because it stores the css_id
> of the memcg.  Using a struct mem_cgroup pointer would be larger and
> also create a reference on the memcg which would hang memcg rmdir
> deletion.  Usage of a css_id is not a reference so cgroup deletion is
> not affected.  The memcg can be deleted without cleaning up the i_memcg
> field.  When a memcg is deleted its pages are recharged to the cgroup
> parent, and the related inode(s) are marked as shared thus
> disassociating the inodes from the deleted cgroup.
> 
> A mem_cgroup_mark_inode_dirty() tracepoint is also included to allow for
> easier understanding of memcg writeback operation.
> 
> Signed-off-by: Greg Thelen <gthelen@google.com>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>


> ---
> Changelog since v8:
> - Use I_MEMCG_SHARED when initializing i_memcg.
> 
> - Use 'memcg' rather than 'mem' for local variables.  This is consistent with
>   other memory controller code.
> 
> - The logic in mem_cgroup_update_page_stat() and mem_cgroup_move_account() which
>   marks inodes I_MEMCG_SHARED is now part of this patch.  This makes more sense
>   because this is that patch that introduces that shared-inode concept.
> 
yes, this makes the patch clearer.

Thanks,
-Kame


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