Re: [RFC PATCH 0/7] mm: Get rid of vmalloc_sync_(un)mappings()

Matthew Wilcox
2020-05-11T15:52:16Z

On Mon, May 11, 2020 at 09:31:34AM +0200, Peter Zijlstra wrote:
> On Sat, May 09, 2020 at 06:11:57PM -0700, Matthew Wilcox wrote:
> > Iterating an XArray (whether the entire thing
> > or with marks) is RCU-safe and faster than iterating a linked list,
> > so this should solve the problem?
>
> It can hardly be faster if you want all elements -- which is I think the
> case here. We only call into this if we change an entry, and then we
> need to propagate that change to all.

Of course it can be faster. Iterating an array is faster than iterating
a linked list because caches. While an XArray is a segmented array
(so slower than a plain array), it's plainly going to be faster than
iterating a linked list.