Re: [PATCH] JBD slab cleanups

Christoph Hellwig
2007-09-17T19:34:59Z

On Mon, Sep 17, 2007 at 12:29:51PM -0700, Mingming Cao wrote:
> The problem with this patch, as Andreas Dilger pointed today in ext4
> interlock call, for 1k,2k block size ext2/3/4, get_free_pages() waste
> 1/3-1/2 page space.
>
> What was the originally intention to set up slabs for committed_data(and
> frozen_buffer) in JBD? Why not using kmalloc?

kmalloc is using slabs :)

The intent was to avoid the wasted memory, but as we've repeated a gazillion
times wasted memory on a rather rare codepath doesn't really matter when
you just crash random storage drivers otherwise.