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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 Thu, 2026-09-17 at 10:42 +0200, David Hildenbrand (Arm) wrote: > On 9/17/26 10:37, Yuan-Hao Hsu wrote: > > GUP-fast grabs a PTE-mapped large folio one page at a time.=C2=A0 Every > > PTE > > costs a try_grab_folio_fast() (a refcount cmpxchg, plus the > > pincount > > atomic, a full barrier and a node stat update for FOLL_PIN), a > > gup_fast_folio_allowed() and a folio_set_referenced(), so a 64 kB > > mTHP > > pays sixteen of each and a PTE-mapped 2 MB THP pays 512.=C2=A0 The PMD > > and > > PUD leaf paths already take the whole range with one > > try_grab_folio_fast() call, and the slow path is getting the same > > treatment for PTEs in Rik's follow_page_mask() series. > >=20 > > IORING_REGISTER_BUFFERS of 1 GB, median of 15: > >=20 > > =C2=A0 64 kB mTHP=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0 6179/5998 us=C2=A0 ->=C2=A0 1599 us > > =C2=A0 1 MB mTHP=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0 5790/5801 us=C2=A0 ->=C2=A0=C2=A0 893 us > > =C2=A0 4 kB pages=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0 7173/6741 us=C2=A0 ->=C2=A0 6763 us > >=20 >=20 > I think Rik was already working on this and sent some patches. > Anyhow, there is > quite some GUP review backlog I have t go through, so this will have > to wait. My patches are for the regular gup path, in follow_pages_mask() This is for the gup_fast path. Unfortunately there is some nearly duplicated code between them. Last I looked I did not find any clear ways to merge them, but I can take another look if you want. --=20 All Rights Reversed.