linux-kernel - Re: [PATCH v6] mm/filemap: remove hugetlb special casing in filemap.c

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Date:   Fri, 18 Aug 2023 11:03:09 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Sidhartha Kumar <sidhartha.kumar@...cle.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        songmuchun@...edance.com, mike.kravetz@...cle.com,
        willy@...radead.org
Subject: Re: [PATCH v6] mm/filemap: remove hugetlb special casing in
 filemap.c

On Thu, 17 Aug 2023 11:18:36 -0700 Sidhartha Kumar <sidhartha.kumar@...cle.com> wrote:

> Perf was used to check the performance differences after the patch. Overall
> the performance is similar to mainline with a very small larger overhead that
> occurs in __filemap_add_folio() and hugetlb_add_to_page_cache(). This is because
> of the larger overhead that occurs in xa_load() and xa_store() as the
> xarray is now using more entries to store hugetlb folios in the page cache.

So... why merge the patch?  To save 40 lines of code?

I mean, if a patch which added 40 lines yielded a "very small"
reduction in overhead, we'd probably merge it!

Or is there some wider reason for this which the changelog omitted?