On Wed, Aug 25, 2010 at 05:30:42PM -0700, David Rientjes wrote: > > We certainly hope that nobody will reimplement the same function without > the __deprecated warning, especially for order < PAGE_ALLOC_COSTLY_ORDER > where there's no looping at a higher level. So perhaps the best > alternative is to implement the same _nofail() functions but do a > WARN_ON(get_order(size) > PAGE_ALLOC_COSTLY_ORDER) instead? Yeah, that sounds better. > I think it's really sad that the caller can't know what the upper bounds > of its memory requirement are ahead of time or at least be able to > implement a memory freeing function when kmalloc() returns NULL. Oh, we can determine an upper bound. You might just not like it. Actually ext3/ext4 shouldn't be as bad as XFS, which Dave estimated to be around 400k for a transaction. My guess is that the worst case for ext3/ext4 is probably around 256k or so; like XFS, most of the time, it would be a lot less. (At least, if data != journalled; if we are doing data journalling and every single data block begins with 0xc03b3998U, we'll need to allocate a 4k page for every single data block written.) We could dynamically calculate an upper bound if we had to. Of course, if ext3/ext4 is attached to a network block device, then it could get a lot worse than 256k, of course. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
