Re: XArray documentation

Martin Steigerwald
2017-11-24T22:02:44Z

Matthew Wilcox - 24.11.17, 22:18:
> On Fri, Nov 24, 2017 at 07:01:31PM +0100, Martin Steigerwald wrote:
> > > The XArray is an abstract data type which behaves like an infinitely
> > > large array of pointers. The index into the array is an unsigned long.
> > > A freshly-initialised XArray contains a NULL pointer at every index.
> >
> > Yes, I think this is clearer already.
> >
> > Maybe with a few sentences on "Why does the kernel provide this?", "Where
> > is it used?" (if already known), "What use case is it suitable for – if I
> > want to implement something into the kernel (or in user space?) ?" and
> > probably "How does it differ from user data structures the kernel
> > provides?"
>
> OK, I think this is getting more useful. Here's what I currently have:
>
> Overview
> ========
>
> The XArray is an abstract data type which behaves like a very large array
> of pointers. It meets many of the same needs as a hash or a conventional
> resizable array. Unlike a hash, it allows you to sensibly go to the
> next or previous entry in a cache-efficient manner. In contrast to
> a resizable array, there is no need for copying data or changing MMU
> mappings in order to grow the array. It is more memory-efficient,
> parallelisable and cache friendly than a doubly-linked list. It takes
> advantage of RCU to perform lookups without locking.

I like this.

I bet I may not be able help much further with it other than to possibly
proofread it tomorrow.

Thank you for considering my suggestion.

--
Martin