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Shenoy" , Ingo Molnar , K Prateek Nayak , Peter Zijlstra Date: Thu, 26 Jun 2025 17:10:24 -0700 In-Reply-To: References: 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 Thu, 2025-06-26 at 21:32 +0800, Chen, Yu C wrote: >=20 > >=20 > > This task work may take a long time for the system with large number= =20 > > cpus which increacing the delay for process back to userspace. It may b= e=20 > > the reason that schbench benchmark regressed so much. > >=20 >=20 > Thanks for the insight Jianyong, yes, the scan on all online CPUs would > be costly. >=20 > > To avoid searching the whole system, what about just searching the=20 > > preferred numa node provided by numa balancing if there is one. If not,= =20 > > then fallback to search the whole system or just search the numa node= =20 > > where the main process locates as there is a high probability it=20 > > contains the preferred LLC. In other words, we can opt for a suboptimal= =20 > > LLC location to prioritize speed. > >=20 > > WDYT? > >=20 > This is a good idea. Previously, Tim had a version that dealt with a > similar scenario, which only scanned the CPUs within p's preferred node. Yes, we were also thinking along the line of looking only at the preferred node. > However, it seems to cause bouncing of the mm->mm_sched_cpu because we > set a 2X threshold for switching the mm->mm_sched_cpu in patch 5. If the > old mm_sched_cpu is not in p's current preferred node, last_m_a_occ is > always 0, which makes the switching of mm->mm_sched_cpu always succeed > due to the condition if (m_a_occ > (2 * last_m_a_occ)).=C2=A0 >=20 There were some regressions on schbench during out tests and preferred LLC bounces switches a lot with preferred node as mentioned by Chen Yu. For schbench, there's really not much NUMA data and preferred node bounces around. We'll have to figure out the right thing to do if preferred node changes and preferred LLC falls outside the preferred node. Tim > Anyway, since it > is a software issue, we can find a way to address it. >=20 > Maybe we also following Abel's suggestion that only one thread of > the process is allowed to perform the statistic calculation, this > could minimal the negative impact to the whole process. >=20