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Wed, 12 Feb 2025 04:07:20 -0800 (PST) Content-Type: text/plain; charset=utf-8 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3826.400.131.1.6\)) Subject: Re: [PATCH v10 09/12] x86/mm: enable broadcast TLB invalidation for multi-threaded processes From: Nadav Amit In-Reply-To: <20250211210823.242681-10-riel@surriel.com> Date: Wed, 12 Feb 2025 14:07:08 +0200 Cc: the arch/x86 maintainers , Linux Kernel Mailing List , Borislav Petkov , peterz@infradead.org, Dave Hansen , zhengqi.arch@bytedance.com, thomas.lendacky@amd.com, kernel-team@meta.com, "open list:MEMORY MANAGEMENT" , Andrew Morton , jackmanb@google.com, jannh@google.com, mhklinux@outlook.com, andrew.cooper3@citrix.com, Manali Shukla Content-Transfer-Encoding: quoted-printable Message-Id: <940E9420-0CD3-4C9A-AFCC-23433AF8EFA4@gmail.com> References: <20250211210823.242681-1-riel@surriel.com> <20250211210823.242681-10-riel@surriel.com> To: Rik van Riel X-Mailer: Apple Mail (2.3826.400.131.1.6) It all looks pretty sane to me. One small note: > On 11 Feb 2025, at 23:08, Rik van Riel wrote: >=20 > +/* > + * Check whether a process is currently active on more than = "threshold" CPUs. > + * This is a cheap estimation on whether or not it may make sense to = assign > + * a global ASID to this process, and use broadcast TLB invalidation. > + */ > +static bool mm_active_cpus_exceeds(struct mm_struct *mm, int = threshold) > +{ > + int count =3D 0; > + int cpu; > + > + /* This quick check should eliminate most single threaded = programs. */ > + if (cpumask_weight(mm_cpumask(mm)) <=3D threshold) > + return false; > + Does it make sense to first check mm.mm_users against the threshold? It = might be less cache-contended. Anyhow, for what=E2=80=99s it worth: Reviewed-by: Nadav Amit >