From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) (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 F259F2BFC85 for ; Fri, 22 Aug 2025 19:45:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755891931; cv=none; b=HWqlWATxaLy2wk3KukZoqCoq+pUyXxhS146jVvhEk0vo0/ETii082tPXxwTGm7aJMQ4HskIwiH/rBemaY/ctk628EBPpDUYrFqtu2FnZazpXQ5xWxBOhCvsAmEyKgQA7FNKzW0+2BaGMApntFH50xQ1KpkGYNOdwEOQxD/4Irvs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755891931; c=relaxed/simple; bh=qV4phOwmGE5NrajGHke2b0uxuCpMNYBHbRitW99FBf0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WRc3mwvB1ta39ff05GJz98TLYQSCBF4PtPiTxqtmIKQ8nwSf7UgzB9bb6swwY5vuZa4HjLF6GNh65QJS58Xjrj9Z2NiF27MG5w+u3WOGrTu++nE2we5KHvipzHM5+3z40E9VbQJUAyXg9U/EWUDnA4mdDCARNbBHTW35U7GXrjs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz; spf=pass smtp.mailfrom=suse.cz; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=ykmiMHXH; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=8ObR4Lnm; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=HSCqIWow; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=5IvjwtjP; arc=none smtp.client-ip=195.135.223.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.cz Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="ykmiMHXH"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="8ObR4Lnm"; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="HSCqIWow"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="5IvjwtjP" Received: from localhost (unknown [10.100.12.32]) by smtp-out2.suse.de (Postfix) with ESMTP id 3DB4D1F385; Fri, 22 Aug 2025 19:45:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1755891924; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M5BMf9ITNHHswVF8PEaR4ndhiHkQMiVdrHDz6mV2kqc=; b=ykmiMHXHLywLlKWjovo3wMuBcC9OjXvHVvce6gInHppO160d3pLS8/SrRRVF2S7uBCIXZN /TDKK3Q3LH4qHUP/InW/qwRBfjzf10szxomjSTez2KQEBXU/yRASH8URciJUpoWKqvaIU9 hZh3j9+o9t62Cqm/Oy7tkjVudO1R490= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1755891924; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M5BMf9ITNHHswVF8PEaR4ndhiHkQMiVdrHDz6mV2kqc=; b=8ObR4LnmFAY8qgrZNVVRXc4AEdVPIGwSTKlkycqJmnmTzBuvxefddvHRRHQOmQ2eY9lApm nVuNuXMXx5Ks2kCQ== Authentication-Results: smtp-out2.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1755891923; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M5BMf9ITNHHswVF8PEaR4ndhiHkQMiVdrHDz6mV2kqc=; b=HSCqIWowAoEW7W7H1kg1QIz7YOTX/lPZC25EHLFYieanmwvbLgcy6AszKq9p7q/T6Yzsat 2JYYFEDJ8T0Q/6lh62t5zPQC+RQ1qoZLTJWBeLDnERceL+gq+TFb7QbASvEaLm91a+PuvR ba6H09xtFcOLml5bcZqCaCtDkatCw/s= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1755891923; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M5BMf9ITNHHswVF8PEaR4ndhiHkQMiVdrHDz6mV2kqc=; b=5IvjwtjPKRJF0QEu+8kUY7OpVwMJF+lH0M7tM2br3TvUvgU/iAMHD58k5fjc0nxbJtDw2g r/YyEoscsNhZcLBQ== Date: Fri, 22 Aug 2025 21:45:23 +0200 From: Jiri Bohac To: Breno Leitao Cc: Baoquan He , Vivek Goyal , Dave Young , kexec@lists.infradead.org, akpm@linux-foundation.org, Philipp Rudo , Donald Dutile , Pingfan Liu , Tao Liu , linux-kernel@vger.kernel.org, David Hildenbrand , Michal Hocko Subject: Re: [PATCH v5 0/5] kdump: crashkernel reservation from CMA Message-ID: References: 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 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.983]; MIME_GOOD(-0.10)[text/plain]; MISSING_XM_UA(0.00)[]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_TWELVE(0.00)[13]; ARC_NA(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_COUNT_ZERO(0.00)[0]; MID_RHS_MATCH_FROMTLD(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; DBL_BLOCKED_OPENRESOLVER(0.00)[localhost:helo,suse.cz:email,dwarf.suse.cz:mid] X-Spam-Flag: NO X-Spam-Level: X-Spam-Score: -4.30 On Thu, Aug 21, 2025 at 01:35:35AM -0700, Breno Leitao wrote: > I have another question. I assume it’s not possible to allocate only the > CMA crashkernel area for the kdump kernel, since we need to keep the > loaded kernel in the crashkernel area while the system is running. > Therefore, specifying crashkernel=X (without ',cma') is necessary. exactly > At the same time, since the crashdump environment will use CMA, the > crashkernel area itself doesn’t need to be very large, as the CMA space > will be allocated later. > > With that in mind, how do I find what is the recommended size for the > crashkernel area, assuming the CMA area will be more than sufficient at > runtime? > > Does it need ot be much higher than the size of kdump kernel and initrd? I don't have a good answer now - I have this on my to-do list and I need to investigate this more to come up with a formula to calculate the required size to include this in the kdump tool I maintain for SUSE. When testing the kernel part I used crashkernel=100M crashkernel=XXX,cma on a machine that would normally require something like crashkernel=430M. -- Jiri Bohac SUSE Labs, Prague, Czechia