Re: [RFC][PATCHSET] epoll cleanups

[Al Viro]

On Sun, Oct 04, 2020 at 01:13:29PM +0100, Matthew Wilcox wrote:

> Have you considered just storing a pointer to each struct file in an
> epoll set in an XArray?  Linked lists suck for modern CPUs, and there'd
> be no need to store any additional data in each struct file.  Using
> xa_alloc() to store the pointer and throw away the index the pointer
> got stored at would leave you with something approximating a singly
> linked list, except it's an array.  Which does zero memory allocations
> for a single entry and will then allocate a single node for your first
> 64 entries.

Won't work - those struct file can get freed while we are collecting the
set/allocating epitem/calling ->poll()/etc.