From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0535A36829F for ; Wed, 19 Nov 2025 17:27:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763573230; cv=none; b=WHlEk52jEVhaurRXaAnjSmPoRs5JC6DlwG24ozN70OEb4iWi0pXOMgvod19d37dye2GLKvyHGAPbO3Whj9t/JlJP9hUJ8GrL+hVI3H6TKJZhbUjYER4/a8VdwVI9p4gf85odGwnzwCkcYy9tUJtmQbbG0JOUCsTQqva/5WXO6g8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763573230; c=relaxed/simple; bh=R0xQh8cJXsLSNlv45rkCwhEHl28wT4uMA/N7H6g+0DA=; h=Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type:Date; b=PZdgQVaweHwRcjJqOuXY9zhmWWoygx/yprmyjSz1P+n9Ng2YgjT1WVY3fbvwH3tTCobAx4hqlJMxJtiJMGs6z16gc7/lhxE12ybwbHrSIbN4RRimlzlS1bxD/CfA0ScuT6oKwUxz6DdiJZLoi0vZgmoEzdD/ZWom/DjuAcvROL0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=zDbIoW8u; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=YEgn7edc; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="zDbIoW8u"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="YEgn7edc" Message-ID: <20251119172549.578653738@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1763573222; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=I87MsMc/jocn5JouBwHRM84S3IHfpjCOZBSfWy/Cbeg=; b=zDbIoW8u9/Yo3QgAwJyUr3U54w/rFLiM9kR1RN2PJV3sko0vWMQYL4QIsML6Dg5dED0Uke 993dkDU5yo+7/ke6PxuIfdMa8AH2k0hR4G0+u1odfAtqhJnlQlfzGW/uQG381PZv3VKOXW jHvKgVK/VEBi6AE0F3pkS8r/K1W+NmaT9kbUoN9BtnbHFbTTiTR5UituOu7/L2b5GbLKNs VL6fIiw/yVdwHFtWcEPNB8ffY7XuA56TCm1CzFazfFeh8Eq8L0cvNTl3r03YiCixI/DjHb GZOdIuTh7+coApWPfgbmFAaR7ONUk5hDpQ8lt4z0fRa1jsQXgfskSnrxIwuCvw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1763573222; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=I87MsMc/jocn5JouBwHRM84S3IHfpjCOZBSfWy/Cbeg=; b=YEgn7edcxtLkUVb/H7NtmPcCIMBUKA4zfu8MfZKFtsHJ3Va3dJMPVl7WUb0dMIDK5E4qUC x/d+mj3zKDeNZtAg== From: Thomas Gleixner To: LKML Cc: Peter Zijlstra , Gabriele Monaco , Mathieu Desnoyers , Michael Jeanson , Jens Axboe , "Paul E. McKenney" , "Gautham R. Shenoy" , Florian Weimer , Tim Chen , Yury Norov , Shrikanth Hegde Subject: [patch V5 09/20] cpumask: Cache num_possible_cpus() References: <20251119171016.815482037@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Date: Wed, 19 Nov 2025 18:27:01 +0100 (CET) Reevaluating num_possible_cpus() over and over does not make sense. That becomes a constant after init as cpu_possible_mask is marked ro_after_init. Cache the value during initialization and provide that for consumption. Signed-off-by: Thomas Gleixner Reviewed-by: Yury Norov Reviewed-by: Mathieu Desnoyers Reviewed-by: Shrikanth Hegde --- V4: Add comment why this is not marked __init .... V2: New patch --- include/linux/cpumask.h | 10 ++++++++-- kernel/cpu.c | 19 +++++++++++++++++++ 2 files changed, 27 insertions(+), 2 deletions(-) --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -126,6 +126,7 @@ extern struct cpumask __cpu_dying_mask; #define cpu_dying_mask ((const struct cpumask *)&__cpu_dying_mask) extern atomic_t __num_online_cpus; +extern unsigned int __num_possible_cpus; extern cpumask_t cpus_booted_once_mask; @@ -1152,13 +1153,13 @@ void init_cpu_possible(const struct cpum #define __assign_cpu(cpu, mask, val) \ __assign_bit(cpumask_check(cpu), cpumask_bits(mask), (val)) -#define set_cpu_possible(cpu, possible) assign_cpu((cpu), &__cpu_possible_mask, (possible)) #define set_cpu_enabled(cpu, enabled) assign_cpu((cpu), &__cpu_enabled_mask, (enabled)) #define set_cpu_present(cpu, present) assign_cpu((cpu), &__cpu_present_mask, (present)) #define set_cpu_active(cpu, active) assign_cpu((cpu), &__cpu_active_mask, (active)) #define set_cpu_dying(cpu, dying) assign_cpu((cpu), &__cpu_dying_mask, (dying)) void set_cpu_online(unsigned int cpu, bool online); +void set_cpu_possible(unsigned int cpu, bool possible); /** * to_cpumask - convert a NR_CPUS bitmap to a struct cpumask * @@ -1211,7 +1212,12 @@ static __always_inline unsigned int num_ { return raw_atomic_read(&__num_online_cpus); } -#define num_possible_cpus() cpumask_weight(cpu_possible_mask) + +static __always_inline unsigned int num_possible_cpus(void) +{ + return __num_possible_cpus; +} + #define num_enabled_cpus() cpumask_weight(cpu_enabled_mask) #define num_present_cpus() cpumask_weight(cpu_present_mask) #define num_active_cpus() cpumask_weight(cpu_active_mask) --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -3108,6 +3108,9 @@ EXPORT_SYMBOL(__cpu_dying_mask); atomic_t __num_online_cpus __read_mostly; EXPORT_SYMBOL(__num_online_cpus); +unsigned int __num_possible_cpus __ro_after_init = NR_CPUS; +EXPORT_SYMBOL(__num_possible_cpus); + void init_cpu_present(const struct cpumask *src) { cpumask_copy(&__cpu_present_mask, src); @@ -3116,6 +3119,7 @@ void init_cpu_present(const struct cpuma void init_cpu_possible(const struct cpumask *src) { cpumask_copy(&__cpu_possible_mask, src); + __num_possible_cpus = cpumask_weight(&__cpu_possible_mask); } void set_cpu_online(unsigned int cpu, bool online) @@ -3139,6 +3143,21 @@ void set_cpu_online(unsigned int cpu, bo } } +/* + * This should be marked __init, but there is a boatload of call sites + * which need to be fixed up to do so. Sigh... + */ +void set_cpu_possible(unsigned int cpu, bool possible) +{ + if (possible) { + if (!cpumask_test_and_set_cpu(cpu, &__cpu_possible_mask)) + __num_possible_cpus++; + } else { + if (cpumask_test_and_clear_cpu(cpu, &__cpu_possible_mask)) + __num_possible_cpus--; + } +} + /* * Activate the first processor. */