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Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1pNuDQ-005UiC-0J; Fri, 03 Feb 2023 11:26:48 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 7D82330012F; Fri, 3 Feb 2023 12:27:23 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 69BB5212BDE63; Fri, 3 Feb 2023 12:27:23 +0100 (CET) Date: Fri, 3 Feb 2023 12:27:23 +0100 From: Peter Zijlstra To: Raghavendra K T Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar , Mel Gorman , Andrew Morton , David Hildenbrand , rppt@kernel.org, Bharata B Rao , Disha Talreja Subject: Re: [PATCH V2 2/3] sched/numa: Enhance vma scanning logic Message-ID: References: <5f0872657ddb164aa047a2231f8dc1086fe6adf6.1675159422.git.raghavendra.kt@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: ECFC41C000A X-Rspam-User: X-Stat-Signature: xk18mifucxt9qmzophqwf4tr4w9dhtmd X-HE-Tag: 1675423650-136900 X-HE-Meta: U2FsdGVkX18s6bWGPxqCGpehEIxfg8ChbEJhZVPWIRjNwaf5Q9tMMEyqmqnjwKOLtPWsJbRunVY0n4tm4mEhZWb36Gd9wtzkX7MDAAR4yiwSr9u5Sz6TnLnUuJvcJtoQdrQ84apzNOa5XvzSNoneVpCqHLcBoDtnxxFqtRac8S6jiVtY3kuGKE1BqqsRhRVwdCPGojSkqypU+X+PQWLD2Y6WnKPGOtu+YEkIx3mZeLEsTzQYDbHbjXophcDi5FSaha0lLVfPFbst5VtPmDBJDTmaC/atxmByw7XYkMQF1oxwtGpQu60fn1HlcciZTGhc1bdHJ45z2WECcroJ0uYU+jfsxYJBbuEMnrui4hM0OFR65FlEbsBPSo/O6GY8lkZ5QviNedPQZvlXuSX1c+V1iErq4UUkZhshTNv6zuWVhdAfaEGNXYaCOibf9SX8kW9WgvBU6A8AmqEdVffmOaObeFsam77+UrCu/QUjWf9Q0QV7KYF8MJ69RebqVEh6cc4DiaeLzZEVIvMv/A2W0grgaUyUa485Nq1kiJmM/3WYsHSDjgke6ut99mYuMDpJIzlPHGmChzldGkgICJ1xLNlpXtVpkcc9FP++jMGSnJteoIF72EI0ZbvQeH2zoINZxbooCMUk3XVNWatOR6IFZw4e7/sxfE5ZoQzDq+c7P547Y+5GuxrzpSNpqXOMTOW8VEGP6xr8DDeZYLN0vt7X88Ktg0NYrdok/wuUTDr6MF5IB/FTKNq6teC8yyKiZw67tj4YRn7ll/+pHZeDsKrNEZ9Dx7la0DOacc7aXOB0nRzuZIVP3YrMdSjsPUimZ4JSuhNQHBbcDxT2+Kis1HpJ0ePEts8hunq8iwT9JMfxoxwpx0+VHJY4TuAyLEhfAD9MnmZNGl9aedndAVDzyDQ8A+miEFlIV2mdjyc7FgY1PO4oDuGuyCTfIvAYA1JdLyaHmUA+hDXHNM38wicJjrtC0UP I5egdPk2 +zwtRr90f4Wme4XkzqtfgoUufOs2xTrmpBazHPgHT4bxTx7LWEol9yN7dlp+62s5cNl53o09FZQqg1u8Y18/N/wnJjLr7B5Tk+7deVR58C4D4D7bKCXk7GSShgcP0wJ78CqzpS8VpbDzqbfphSMNrmj+ZPg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Feb 03, 2023 at 12:15:48PM +0100, Peter Zijlstra wrote: > > +static inline void vma_set_active_pid_bit(struct vm_area_struct *vma) > > +{ > > + unsigned int active_pid_bit; > > + > > + if (vma->numab) { > > + active_pid_bit = current->pid % BITS_PER_LONG; > > + vma->numab->accessing_pids |= 1UL << active_pid_bit; > > + } > > +} > > Perhaps: > > if (vma->numab) > __set_bit(current->pid % BITS_PER_LONG, &vma->numab->pids); > > ? > > Or maybe even: > > bit = current->pid % BITS_PER_LONG; > if (vma->numab && !__test_bit(bit, &vma->numab->pids)) > __set_bit(bit, &vma->numab->pids); > The alternative to just taking the low n bits is to use: hash_32(current->pid, BITS_PER_LONG) That mixes things up a bit.