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Shenoy" Date: Wed, 02 Jul 2025 14:47:01 -0700 In-Reply-To: <85bff038-6bc8-4643-8a15-89ac435206fd@linux.ibm.com> References: <7371f30196b317c0c5a0ae3fa463ec76a4dc69ef.1750268218.git.tim.c.chen@linux.intel.com> <85bff038-6bc8-4643-8a15-89ac435206fd@linux.ibm.com> Autocrypt: addr=tim.c.chen@linux.intel.com; prefer-encrypt=mutual; keydata=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 iQFUBBMBCAA+FiEEEsKdz9s94XWwiuG96lQbuGeTCYsFAlwLCmACGwMFCQHhM4AFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AACgkQ6lQbuGeTCYuQiQf9G2lkrkRdLjXehwCl+k5zBkn8MfUPi2ItU2QDcBit/YyaZpNlSuh8h30gihp5Dlb9BnqBVKxooeIVKSKC1HFeG0AE28TvgCgEK8qP/LXaSzGvnudek2zxWtcsomqUftUWKvoDRi1AAWrPQmviNGZ4caMd4itKWf1sxzuH1qF5+me6eFaqhbIg4k+6C5fk3oDBhg0zr0gLm5GRxK/lJtTNGpwsSwIJLtTI3zEdmNjW8bb/XKszf1ufy19maGXB3h6tA9TTHOFnktmDoWJCq9/OgQS0s2D7W7f/Pw3sKQghazRy9NqeMbRfHrLq27+Eb3Nt5PyiQuTE8JeAima7w98quQ== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 (3.50.4-1.fc39) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2025-07-02 at 12:17 +0530, Madadi Vineeth Reddy wrote: > Hi Tim, >=20 > On 18/06/25 23:57, Tim Chen wrote: > > Switching a process's preferred LLC generates lots of task > > migrations across LLCs. To avoid frequent switches > > of home LLC, implement the following policy: > >=20 > > 1. Require a 2x occ change threshold to switch preferred LLC > > 2. Don't discard preferred LLC for a task > >=20 > > Signed-off-by: Tim Chen > > --- > > kernel/sched/fair.c | 24 ++++++++++++++++-------- > > 1 file changed, 16 insertions(+), 8 deletions(-) > >=20 > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 6a2678f9d44a..7fb2322c5d9e 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -1175,6 +1175,14 @@ static s64 update_curr_se(struct rq *rq, struct = sched_entity *curr) > > #define EPOCH_PERIOD (HZ/100) /* 10 ms */ > > #define EPOCH_OLD 5 /* 50 ms */ > > =20 > > +static int llc_id(int cpu) > > +{ > > + if (cpu < 0) > > + return -1; > > + > > + return per_cpu(sd_llc_id, cpu); > > +} > > + > > void mm_init_sched(struct mm_struct *mm, struct mm_sched __percpu *_pc= pu_sched) > > { > > unsigned long epoch; > > @@ -1299,6 +1307,7 @@ static void task_cache_work(struct callback_head = *work) > > struct task_struct *p =3D current; > > struct mm_struct *mm =3D p->mm; > > unsigned long m_a_occ =3D 0; > > + unsigned long last_m_a_occ =3D 0; > > int cpu, m_a_cpu =3D -1; > > cpumask_var_t cpus; > > =20 > > @@ -1337,11 +1346,13 @@ static void task_cache_work(struct callback_hea= d *work) > > per_cpu(sd_llc_id, i), occ, m_occ, m_cpu, nr); > > } > > =20 > > - a_occ /=3D nr; > > + // a_occ /=3D nr; >=20 > Is the above by mistake? > I think we need to have average only and not the total value as that favo= rs LLCs with > larger size. >=20 Actually Chen Yu and I have gone back and forth on this one. A different perspective is dividing by nr will disfavor LLCs of larger size. You will need way more tasks in larger LLC to put the tasks there, which may cause over-stacking on the smaller LLC. We find that not dividing by nr is more stable when we bring CPU online/offline. =20 Tim > Thanks, > Madadi Vineeth Reddy >=20 > > if (a_occ > m_a_occ) { > > m_a_occ =3D a_occ; > > m_a_cpu =3D m_cpu; > > } > > + if (llc_id(cpu) =3D=3D llc_id(mm->mm_sched_cpu)) > > + last_m_a_occ =3D a_occ; > > =20 > > trace_printk("(%d) a_occ: %ld m_a_occ: %ld\n", > > per_cpu(sd_llc_id, cpu), a_occ, m_a_occ); > > @@ -1355,13 +1366,10 @@ static void task_cache_work(struct callback_hea= d *work) > > } > > } > > =20 > > - /* > > - * If the max average cache occupancy is 'small' we don't care. > > - */ > > - if (m_a_occ < (NICE_0_LOAD >> EPOCH_OLD)) > > - m_a_cpu =3D -1; > > - > > - mm->mm_sched_cpu =3D m_a_cpu; > > + if (m_a_occ > (2 * last_m_a_occ)) { > > + /* avoid the bouncing of mm_sched_cpu */ > > + mm->mm_sched_cpu =3D m_a_cpu; > > + } > > =20 > > free_cpumask_var(cpus); > > } >=20