From nobody Wed Dec 17 08:17:14 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 041E2C4332F for ; Tue, 12 Dec 2023 04:21:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229626AbjLLEVV (ORCPT ); Mon, 11 Dec 2023 23:21:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56594 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229547AbjLLEVK (ORCPT ); Mon, 11 Dec 2023 23:21:10 -0500 Received: from mail-oo1-xc35.google.com (mail-oo1-xc35.google.com [IPv6:2607:f8b0:4864:20::c35]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 640CBBF for ; Mon, 11 Dec 2023 20:21:17 -0800 (PST) Received: by mail-oo1-xc35.google.com with SMTP id 006d021491bc7-59067ccb090so3240739eaf.1 for ; Mon, 11 Dec 2023 20:21:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1702354876; x=1702959676; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=UfvFAKot0bp3HfeoPJ3dMZk7rFg3lsuy8X5EAYhpV4g=; b=nGV5ZDxr70D91ac+T6LqL8u3ojak+2fWxoTFlSoCTx3A9EXgpYNgjkIMN+wEHM30jH IkL5aDwYTG1BsCF0/VG/DWrr9JULuYCxT1R+/4IA8CxftbJrTVt5V8m0ydaJGKWcty9a TGpec6p6evfw+K801vNqDNlTLaMzFKCeigNUY5O85fW675gVFe38VV32mIFmiqzAeKoM o/buveCT4PxWa7yGqy+oNSVWj1Fu3RW1dbQMoRRDxJTBNgG7NwXQ0X2nIq2mA1VKqekc qYxFk+8X2OxG5h0VjhnbqdVvGZmfKkwY0Df5dzvicy5vggb5v6rvulsl9DOA1y+t6K+b a8sg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1702354876; x=1702959676; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=UfvFAKot0bp3HfeoPJ3dMZk7rFg3lsuy8X5EAYhpV4g=; b=wI+6EWXHVdVeuqL3bYdM/Qtg2BaG9EF7HLytX3T7/nm5VxQ9/93o+CrLvUSWH58KrD b9gizSb7T3O9AhnlW7AGTxKLT7a+WRL7HqTJqdhmwJcILtEUpF12k0AxXuRgPoPXoUpU m8aCT5eZrauGnFgAkMIFJu+luQlxWsLKk7sHqthyYRQRaPCjWb477X9TAddKzKqUvRq5 Qvg5WlaEvBTwKpUAlgjRFYYWkYFz0CCMHsnKnxGH4cagKDyB0M64E42EvgbLZ5sEK/Yp 2Ra5siquBDNcuyZOKPUrwh5QTM5et0ApWzWgmY+Ab+gBIHQEf6gVCjIwsVLM8806l9PO trrQ== X-Gm-Message-State: AOJu0YzQoitEZ92VwebKKkyr7KtckFyJ2+wMkGkEefDTZtG9mh1ifmeo GyvOO3LO3urg/yp7U6DrZOs= X-Google-Smtp-Source: AGHT+IHtPBBe0oc/SwS4zRYwzLNnU7oeIKh41ypn77HlaZZ4UfICRn76rQMWuKxSuSM02lrwwpsltA== X-Received: by 2002:a05:6870:4590:b0:1fa:26b7:af18 with SMTP id y16-20020a056870459000b001fa26b7af18mr5327160oao.17.1702354876515; Mon, 11 Dec 2023 20:21:16 -0800 (PST) Received: from localhost ([2601:344:8301:57f0:38aa:1c88:df05:9b73]) by smtp.gmail.com with ESMTPSA id d201-20020a814fd2000000b005cc5f5aa533sm3499620ywb.43.2023.12.11.20.21.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 Dec 2023 20:21:16 -0800 (PST) From: Yury Norov To: Andrew Morton , Thomas Gleixner , Ming Lei , linux-kernel@vger.kernel.org Cc: Yury Norov , Andy Shevchenko , Rasmus Villemoes Subject: [PATCH v3 4/7] lib/group_cpus: optimize outer loop in grp_spread_init_one() Date: Mon, 11 Dec 2023 20:21:04 -0800 Message-Id: <20231212042108.682072-5-yury.norov@gmail.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231212042108.682072-1-yury.norov@gmail.com> References: <20231212042108.682072-1-yury.norov@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Similarly to the inner loop, in the outer loop we can use for_each_cpu() macro, and skip CPUs that have been copied. With this patch, the function becomes O(1), despite that it's a double-loop. Signed-off-by: Yury Norov --- lib/group_cpus.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/lib/group_cpus.c b/lib/group_cpus.c index 7ac94664230f..cded3c8ea63b 100644 --- a/lib/group_cpus.c +++ b/lib/group_cpus.c @@ -17,16 +17,11 @@ static void grp_spread_init_one(struct cpumask *irqmsk,= struct cpumask *nmsk, const struct cpumask *siblmsk; int cpu, sibl; =20 - for ( ; cpus_per_grp > 0; ) { - cpu =3D cpumask_first(nmsk); - - /* Should not happen, but I'm too lazy to think about it */ - if (cpu >=3D nr_cpu_ids) - return; - + for_each_cpu(cpu, nmsk) { __cpumask_clear_cpu(cpu, nmsk); __cpumask_set_cpu(cpu, irqmsk); - cpus_per_grp--; + if (cpus_per_grp-- =3D=3D 0) + return; =20 /* If the cpu has siblings, use them first */ siblmsk =3D topology_sibling_cpumask(cpu); @@ -37,6 +32,7 @@ static void grp_spread_init_one(struct cpumask *irqmsk, s= truct cpumask *nmsk, __cpumask_set_cpu(sibl, irqmsk); if (cpus_per_grp-- =3D=3D 0) return; + cpu =3D sibl + 1; } } } --=20 2.40.1