Re: [PATCH 1/2] Revert "page cache: fix page_cache_next/prev_miss off by one"

[Andrew Morton]

On Wed, 21 Jun 2023 14:24:02 -0700 Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:

> This reverts commit 9425c591e06a9ab27a145ba655fb50532cf0bcc9
> 
> The reverted commit fixed up routines primarily used by readahead code
> such that they could also be used by hugetlb.  Unfortunately, this
> caused a performance regression as pointed out by the Closes: tag.
> 
> The hugetlb code which uses page_cache_next_miss will be addressed in
> a subsequent patch.

Often these throughput changes are caused by rather random
alignment/layout changes and the code change itself was innocent.

Do we have an explanation for this regression, or was it a surprise?