From: Kiryl Shutsemau <kirill@shutemov.name>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com, Zi Yan <ziy@nvidia.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
"Liam R . Howlett" <liam@infradead.org>,
Nico Pache <nico.pache@linux.dev>,
Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
Barry Song <baohua@kernel.org>,
Lance Yang <lance.yang@linux.dev>,
Usama Arif <usama.arif@linux.dev>,
Vlastimil Babka <vbabka@kernel.org>,
Jann Horn <jannh@google.com>
Subject: Re: [PATCH 00/12] mm/collapse: separate a collapse from its callers
Date: Mon, 7 Sep 2026 11:28:03 +0100 [thread overview]
Message-ID: <ap6RNHS_ve88ijLo@thinkstation> (raw)
In-Reply-To: <20260905172342.72be31534af21871f8b13f47@linux-foundation.org>
On Sat, Sep 05, 2026 at 05:23:42PM -0700, Andrew Morton wrote:
> > Behaviour
> > =========
> >
> > Nothing here changes what gets collapsed. Three things a reader should
> > not have to find in the diff:
> >
> > - Patch 5: khugepaged fills its policy once per scan pass, so the
> > max_ptes_* limits and the defrag setting behind the allocation mask are
> > sampled once per pass rather than once per table. A table scanned early
> > in a pass and one scanned late are then judged alike, where before a
> > knob written mid-pass split them.
> >
> > - Patch 8: mm_khugepaged_scan_pmd fires before mm_collapse_huge_page
> > rather than after it, the scan having returned before the collapse
> > runs. Its status field already reads SCAN_SUCCEED for an accepted
> > table, so nothing changes there; what the collapse then made of the
> > table is mm_collapse_huge_page's to report, per order.
> >
> > - Patch 10: which orders a table is scanned for is sampled once per VMA
> > rather than once per table. It cannot widen what a collapse does --
> > the order is tested again under the lock the collapse retakes.
>
> So is *any* functional change expected with this series?
No.
The three items here are so nobody has to find them in the diff, and
calling them behaviour changes is a stretch: a sysfs knob written
mid-pass takes effect on the next pass instead of the next table, and a
tracepoint fires a few lines earlier with the same arguments.
> I'm reluctant to merge an unreviewed v1, but this comes close! I'll
> sit on it for a week or less, see what people say. Please poke me
> if/when you think it's good for mm-new.
Zi and Baolin have already provided enough feedback to justify v2.
--
Kiryl Shutsemau / Kirill A. Shutemov
prev parent reply other threads:[~2026-09-07 10:28 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-04 15:10 [PATCH 00/12] mm/collapse: separate a collapse from its callers Kiryl Shutsemau
2026-09-04 15:10 ` [PATCH 01/12] mm/khugepaged: drop redundant mm_struct pin in madvise_collapse() Kiryl Shutsemau
2026-09-04 15:58 ` Zi Yan
2026-09-07 7:33 ` Baolin Wang
2026-09-04 15:10 ` [PATCH 02/12] mm/khugepaged: count collapses where khugepaged makes them Kiryl Shutsemau
2026-09-05 2:25 ` Zi Yan
2026-09-07 7:40 ` Baolin Wang
2026-09-04 15:10 ` [PATCH 03/12] mm/khugepaged: rename mthp_present_ptes bitmap to eligible_ptes Kiryl Shutsemau
2026-09-05 2:28 ` Zi Yan
2026-09-07 7:54 ` Baolin Wang
2026-09-07 10:35 ` Kiryl Shutsemau
2026-09-04 15:10 ` [PATCH 04/12] mm/collapse: add collapse.h for the collapse interface Kiryl Shutsemau
2026-09-05 2:36 ` Zi Yan
2026-09-07 10:41 ` Kiryl Shutsemau
2026-09-07 8:04 ` Baolin Wang
2026-09-04 15:10 ` [PATCH 05/12] mm/collapse: state what a collapse may do in the policy Kiryl Shutsemau
2026-09-05 2:44 ` Zi Yan
2026-09-07 10:49 ` Kiryl Shutsemau
2026-09-07 19:40 ` Zi Yan
2026-09-07 9:05 ` Baolin Wang
2026-09-07 10:56 ` Kiryl Shutsemau
2026-09-04 15:10 ` [PATCH 06/12] mm/collapse: drop the collapse_possible() wrapper Kiryl Shutsemau
2026-09-05 2:45 ` Zi Yan
2026-09-07 8:28 ` Baolin Wang
2026-09-04 15:10 ` [PATCH 07/12] mm/collapse: name the per-table scan reset for what it resets Kiryl Shutsemau
2026-09-05 18:05 ` Zi Yan
2026-09-07 8:31 ` Baolin Wang
2026-09-04 15:10 ` [PATCH 08/12] mm/collapse: separate scanning a PTE table from collapsing it Kiryl Shutsemau
2026-09-06 2:30 ` Zi Yan
2026-09-07 11:34 ` Kiryl Shutsemau
2026-09-04 15:10 ` [PATCH 09/12] mm/collapse: open-code collapse_single_pmd() in its two callers Kiryl Shutsemau
2026-09-04 15:10 ` [PATCH 10/12] mm/collapse: work out the orders a VMA allows once per VMA Kiryl Shutsemau
2026-09-04 15:10 ` [PATCH 11/12] mm/collapse: declare the collapse interface in collapse.h Kiryl Shutsemau
2026-09-04 15:10 ` [PATCH 12/12] mm/collapse: implement MADV_COLLAPSE in madvise.c Kiryl Shutsemau
2026-09-06 0:23 ` [PATCH 00/12] mm/collapse: separate a collapse from its callers Andrew Morton
2026-09-07 10:28 ` Kiryl Shutsemau [this message]
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