From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr2-f34.google.com (mail-wr2-f34.google.com [74.125.225.98]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AEAB63BE17D for ; Tue, 29 Sep 2026 15:08:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.225.98 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790694532; cv=none; b=GOMuhp97bs+cRTXOwj0rKTl1KREa/qbV1VJyrhnQD0ebPBV93bjeSuB5+M02vup+9ktpCo1LYIkFUpRn6uRM03+OaBMctN91/9X1/dWtf+bgU2Eg3oK4zJ0SebTLtEBQtZGzpyB7xQXD+IXyuhIlA5ex6pHB+o7puRiOH5ogD2M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790694532; c=relaxed/simple; bh=1vm8W791i+oyZX52KOmmX+Et2MEUrtULENJgW2hzL3U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JZfHeMs60fwgm8S28d3uGFyN+0C3WwPU2cf3a80Hl97izwz3SvuqiuRkJDnHeBPpFMKrNGIzFfY5T09Kebg57PYWyoqnhad/Ut2KAoEb/BajxDY0yAo0xWi9dfxu52HhkLsTEvzDnHDU2JKkWSgXnLavAMknWWJEy3q/giBPPx0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com; spf=pass smtp.mailfrom=suse.com; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b=OfLpl+qM; arc=none smtp.client-ip=74.125.225.98 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b="OfLpl+qM" Received: by mail-wr2-f34.google.com with SMTP id ffacd0b85a97d-48af9f88c95so196469f8f.0 for ; Tue, 29 Sep 2026 08:08:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1790694513; x=1791299313; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=dnceoXDgkpFRLenSH/o1spO3Q3H0E/MswX6GkcSHu0w=; b=OfLpl+qMH77WcnsVV0mz/HbEty4tCBbv3g7RhVUa8/jZadfQLfJGiJiv0Yd2P4Ji/m 6aUzNBwhh6HuGwf9niZzAFLss9dzdLGemuo7wTSrrLK89yOyGqYY4swJ9BJm9wae0an5 Qrf3gS+ZjmQbjNHvLhSI8MyD6IE7S1Am5grm0Sn+oHWbNIVEqpJ5EBjl+k20OOOgZJwP 075yWHlZR7a15YM5j6R3f/MyZR4dHf21PvOPirIA1XapEJnBCxPIIqER0ymm+OiZu4Zp o7G4M/nynAFISr6YaLeElh6Uj65moxg2HO9GG+YdA+JTa6VV7tffZAYmUFgoq6prr9dw hQ4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790694513; x=1791299313; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=dnceoXDgkpFRLenSH/o1spO3Q3H0E/MswX6GkcSHu0w=; b=BMwG+bdHQf/O0EN+u3LTzyzZaBTScUh+GEX0+HcpQLJsNoE7Tdetf1GIb6k1WgaD90 8noOdPKWOIskf+61oIPs7NrRSBm0Bl18IH4UFmW4oZKx6fMk2g9pMdE2rNT81sOaMRof sDfBVXvaKqsWhXhMceYR1gzgKi7u88mVDJgVKZJdYy/1RlsIH3qDn67BO/xD+7auspge afftgjhMQF21RFRUVuJj9Dn0YTuDD/SfLzEn5pT65FwN8DlIEVBzMaKwwlspIpYA8ypV dWALU8D9yRgTPp3Ik/vcKvJQP/qAr1/rfDcMChbBmn5c5qOgtgBk8LzBA39W751AiGbU BUzA== X-Forwarded-Encrypted: i=1; AKwUvBwmR3j3M56sZ5zDl76TVN9Qqn+O2i2k3I9gEu60BYf5/LgbDaAtSL+V3ivQ6ZeIE0aDeAFV1k1ZRqkDF3E=@vger.kernel.org X-Gm-Message-State: AFuF++kJYSvJlj6+aaXzLx9AxQBznO1zr7ZCJ6XiZ2KDW00e2H56ME5b e9WybSxa/KMgBv1bXEn/bPgzg4wvn3AhKutrEuHttr0BmamremJ242KH9ScdRabB1/Y= X-Gm-Gg: AYBFou2wpILRsg/LuPn/PPmWvj+lpv8CVoPc2kYMGovCrSgaB52qfh29grfHgZ05fU4 oeZJkDBwEwd33auqRgJpXgT+jmdKndeKAkWyxmKv4f71f6x2YxIfrnfD2Kbbo4A2wvLNG1whObD bIWfHvVRmAPuagi/YfuY3T8NiDFp/sijVpFuuSZbdaALGZyXJDkQZMeBuLOCQVM89NXHPv0IQfL kx5pqQPcQmojlP3qPNheYQbLOsjrYfRpQB4XhnhOCyiy9M4RoaI/UhG8hkthY+kLjB7s9u+CVog 7v5WxGLWZDDY30WzQMvldasIWKB5FcC+0F+dwM9AYy/De+cAD8UFxXrd7dqAbFbGq4XjbaL4FVj EkEYZsa0c9fMN+70CQOqZrTaUgPPXoCwxuryHh1HkZOZy3QBRKhLf360Pw0hFsd76qHOp+LBmHR 1gKmGq+AO8bUz1gwJqaFy2l0tqGicfgIHOv9lb/Lk4HT+EOapAiWpZclfhys2qvay9O4z7zuY3v 2upkq4BNAgKA6c= X-Received: by 2002:a05:600c:8b10:b0:49f:fbad:29ae with SMTP id 5b1f17b1804b1-4a00d780b78mr53514925e9.17.1790694513382; Tue, 29 Sep 2026 08:08:33 -0700 (PDT) Received: from pathway.suse.cz (nat2.prg.suse.com. [195.250.132.146]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a00cf9b72fsm113635015e9.9.2026.09.29.08.08.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Sep 2026 08:08:32 -0700 (PDT) Date: Tue, 29 Sep 2026 17:08:30 +0200 From: Petr Mladek To: Sang-Heon Jeon Cc: John Ogness , linux-kernel@vger.kernel.org, Sergey Senozhatsky , Steven Rostedt Subject: Re: [PATCH v2] printk: increase the ring buffer for more than 16 CPUs by default Message-ID: References: <20260927091756.50831-1-ekffu200098@gmail.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20260927091756.50831-1-ekffu200098@gmail.com> On Sun 2026-09-27 18:17:54, Sang-Heon Jeon wrote: > The default LOG_BUF_SHIFT is 17, which means 128 KB, and > LOG_CPU_MAX_BUF_SHIFT is 12, which means 4 KB per CPU. > > By default the ring buffer is increased when > (num_possible_cpus() - 1) * 4 KB > 64 KB, which requires more than 17 > CPUs. > > Remove the explicit subtraction of one, so the ring buffer is increased > for more than 16 CPUs, which is a power of two. Also fix the outdated > comment. > > Suggested-by: Petr Mladek > Signed-off-by: Sang-Heon Jeon JFYI, the patch has been comitted into printk/linux.git, branch for-7.4. Best Regards, Petr