On Mon, Jul 12, 2021 at 04:04:44AM +0100, Matthew Wilcox (Oracle) wrote:

Managing memory in 4KiB pages is a serious overhead.  Many benchmarks
benefit from a larger "page size".  As an example, an earlier iteration
of this idea which used compound pages (and wasn't particularly tuned)
got a 7% performance boost when compiling the kernel.

Using compound pages or THPs exposes a weakness of our type system.
Functions are often unprepared for compound pages to be passed to them,
and may only act on PAGE_SIZE chunks.  Even functions which are aware of
compound pages may expect a head page, and do the wrong thing if passed
a tail page.

We also waste a lot of instructions ensuring that we're not looking at
a tail page.  Almost every call to PageFoo() contains one or more hidden
calls to compound_head().  This also happens for get_page(), put_page()
and many more functions.

This patch series uses a new type, the struct folio, to manage memory.
It converts enough of the page cache, iomap and XFS to use folios instead
of pages, and then adds support for multi-page folios.  It passes xfstests
(running on XFS) with no regressions compared to v5.14-rc1.

This seems to miss a changelog vs the previous version.  It also
includes a lot of the follow ups.  I think reviewing a series gets
rather hard at more than 30-ish patches, so chunking it up a little
more would be useful.