Re: [PATCH v4 01/25] mm: Introduce struct folio

From: Nicholas Piggin
Date: Sun Mar 21 2021 - 22:53:28 EST

Excerpts from Matthew Wilcox's message of March 19, 2021 11:25 am:
> On Fri, Mar 19, 2021 at 10:56:45AM +1100, Balbir Singh wrote:
>> On Fri, Mar 05, 2021 at 04:18:37AM +0000, Matthew Wilcox (Oracle) wrote:
>> > A struct folio refers to an entire (possibly compound) page. A function
>> > which takes a struct folio argument declares that it will operate on the
>> > entire compound page, not just PAGE_SIZE bytes. In return, the caller
>> > guarantees that the pointer it is passing does not point to a tail page.
>> >
>> Is this a part of a larger use case or general cleanup/refactor where
>> the split between page and folio simplify programming?
> The goal here is to manage memory in larger chunks. Pages are now too
> small for just about every workload. Even compiling the kernel sees a 7%
> performance improvement just by doing readahead using relatively small
> THPs (16k-256k). You can see that work here:

The 7% improvement comes from cache cold kbuild by improving IO

Just wondering what kind of readahead is enabled by this that can't
be done with base page size.