On Tue, 27 Jul 2010 12:29:49 -0600 Jonathan Corbet <corbet@xxxxxxx> wrote: > On Tue, 27 Jul 2010 16:53:03 +0900 > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > This virt-array allocates a virtally contiguous array via get_vm_area() > > and allows object allocation per an element of array. > > Quick question: this looks a lot like the "flexible array" mechanism > which went in around a year ago, and which is documented in > Documentation/flexible-arrays.txt. I'm not sure we need two of > these... That said, it appears that there are still no users of > flexible arrays. If your virtually-indexed arrays provide something > that flexible arrays don't, perhaps your implementation should replace > flexible arrays? Hmm. As Documentatin/flexible-arrays.txt says, "The down sides are that the arrays cannot be indexed directly, individual object size cannot exceed the system page size, and putting data into a flexible array requires a copy operation. " This virtually-indexed array is - the arrays can be indexed directly. - individual object size can be defined arbitrary. - puttind data into virt-array requires memory allocation via alloc_varray_item(). But, virtyally-indexed array has its own down side, too. - It uses vmalloc() area. This can be very limited in 32bit archs. - It cannot be used in !MMU archs. - It may consume much TLBs because vmalloc area tends not to be backed by hugepage. Especially, I think !MMU case is much different. So, there are functional difference. I implemented this to do quick direct access to objects by indexes. Otherwise, flex-array may be able to provide more generic frameworks. Then, I myself don't think virt-array is a replacemento for flex-array. A discussion "flex-array should be dropped or not" is out of my scope, sorry. I think you can ask to drop it just because it's almost dead without mentioning virt-array. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>