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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-10-19 at 02:26 +0800, Yuan-Hao Hsu wrote: > On Mon, 10 Aug 2026 22:51:57 -0400, Rik van Riel wrote: > > Add follow_pte_batch() and give follow_page_pte_commit() a run > > length. > > Each run starts with a full per-PTE resolve, then > > follow_pte_batch() > > finds how many more PTEs extend it with a pte_same() scan rather > > than a > > re-derivation of each page, and the run is committed with one > > refcount > > grab. Runs stop at folio boundaries, so plain base pages are > > unaffected. >=20 > One side effect worth a sentence in the changelog: with FOLL_TOUCH, > folio_mark_accessed() now runs once per run instead of once per page. > On the classic LRU the first call only sets PG_referenced and the > second one activates the folio, so the old per-page loop activated a > PTE-mapped large folio from its second page on, and a run now leaves > it referenced but inactive. >=20 > Measured with one get_user_pages() call over 2 MB of freshly faulted > 64 kB folios (kprobe on folio_mark_accessed(), flags from > /proc/kpageflags): >=20 > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 before=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 after > =C2=A0 folio_mark_accessed=C2=A0 512 per call=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0 32 per call > =C2=A0 after 1st call=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 32 folios activ= e=C2=A0 32 referenced, 0 active > =C2=A0 after 2nd call=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 32 active=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 32 active >=20 > That matches what the other two paths already do (follow_huge_pmd() > only calls touch_pmd(), GUP-fast only calls folio_set_referenced()), > so it looks like the right outcome.=C2=A0 It is still a visible change in > aging for anything that reaches these folios through get_user_pages() > rather than the fast path. >=20 Nice catch. You are right that this should be in the changelog! I'll get that in for v4. --=20 All Rights Reversed.