linux-kernel - Re: [RFC, PATCH 0/2] Large folios vs. SIGBUS semantics

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Message-ID: <aPckWHAGfH2i3ssV@infradead.org>
Date: Mon, 20 Oct 2025 23:12:40 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Dave Chinner <david@...morbit.com>
Cc: Kiryl Shutsemau <kirill@...temov.name>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Matthew Wilcox <willy@...radead.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>, Rik van Riel <riel@...riel.com>,
	Harry Yoo <harry.yoo@...cle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	"Darrick J. Wong" <djwong@...nel.org>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Kiryl Shutsemau <kas@...nel.org>
Subject: Re: [RFC, PATCH 0/2] Large folios vs. SIGBUS semantics

On Tue, Oct 21, 2025 at 10:28:02AM +1100, Dave Chinner wrote:
> Fundamentally, we really don't care about the mapping/tlb
> performance of the PTE fragments at EOF. Anyone using files large
> enough to notice the TLB overhead improvements from mapping large
> folios is not going to notice that the EOF mapping has a slightly
> higher TLB miss overhead than everywhere else in the file.
> 
> Please jsut fix the regression.

Yeah.  I'm not even sure why we're having this discussion.  The
behavior is mandated, we have test cases for it and there is
literally no practical upside in changing the behavior from what
we've done forever and what is mandated in Posix.