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Howlett" , Vlastimil Babka , Jann Horn , Dev Jain , Luke Yang , jhladky@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/4] mm/mprotect: move softleaf code out of the main function Message-ID: <4621735a-4adf-4683-ab26-6c0baa156dba@lucifer.local> References: <20260319183108.1105090-1-pfalcato@suse.de> <20260319183108.1105090-3-pfalcato@suse.de> <75ce12ec-b83c-4b5a-8084-6037d602aa75@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <75ce12ec-b83c-4b5a-8084-6037d602aa75@kernel.org> X-Stat-Signature: pb9nqnybsqzi1tj7ur6zme3xixyewg9p X-Rspam-User: X-Rspamd-Queue-Id: AEEED40005 X-Rspamd-Server: rspam12 X-HE-Tag: 1774004063-649977 X-HE-Meta: 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 81xTsb9k SN863MfjY2dirBHLa75Ed576i3jL0puXHqZE4NJN6/RrFy7rWMnKcxR32+yzi7Qsa10LwieptVhGg6FziHWowWfRXCWACegT2n7YvsRJC38Uqodt+LBJ6LAhs2ixAf1BimNcYQiquC0Kcu6aUZkCsPN84VWkOgD7xddrgo37fQGBMd5Esm72HFzg47Ctu8FLZRidxlOUjnGCVLMOm/jgsVlv4qRglT80KySIjVrNg+SJawWs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Mar 20, 2026 at 11:07:26AM +0100, David Hildenbrand (Arm) wrote: > On 3/20/26 11:04, Pedro Falcato wrote: > > On Thu, Mar 19, 2026 at 10:33:47PM +0100, David Hildenbrand (Arm) wrote: > >> On 3/19/26 19:31, Pedro Falcato wrote: > >>> Move softleaf change_pte_range code into a separate function. This makes > >>> the change_pte_range() function (or where it inlines) a good bit > >>> smaller. Plus it lessens cognitive load when reading through the > >>> function. > >>> > >>> Signed-off-by: Pedro Falcato > >>> --- > >>> mm/mprotect.c | 128 +++++++++++++++++++++++++++----------------------- > >>> 1 file changed, 68 insertions(+), 60 deletions(-) > >>> > >>> diff --git a/mm/mprotect.c b/mm/mprotect.c > >>> index 1bd0d4aa07c2..8d4fa38a8a26 100644 > >>> --- a/mm/mprotect.c > >>> +++ b/mm/mprotect.c > >>> @@ -211,6 +211,73 @@ static void set_write_prot_commit_flush_ptes(struct vm_area_struct *vma, > >>> commit_anon_folio_batch(vma, folio, page, addr, ptep, oldpte, ptent, nr_ptes, tlb); > >>> } > >>> > >>> +static noinline long change_pte_softleaf(struct vm_area_struct *vma, > >> > >> Why the noinline? This sounds like something that works good on some > >> CPUs and bad on others, no? > >> > > > > If you don't like the noinline I can always remove it, > > Yes, please. It's easier to argue about __always_inline and constant > propagation than "this code is too scary big for my CPU so I better do > an expensive function call if the code is actually needed". It would make this much more acceptable as a change in general for sure, as it is already good from a code readability point of view. Sometimes that and perf align nicely it seems... :) I do worry about some of these things that might be fine on x86-64, but will somehow be a total problem on other real architectures (i.e. 64 bit). > > -- > Cheers, > > David Cheers, Lorenzo