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.
