From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [RFC PATCH] ia64: convert to dynamic percpu allocator Date: Wed, 12 Aug 2009 15:56:05 +0900 Message-ID: <4A826785.4000509@kernel.org> References: <4A65B0AB.5000608@kernel.org> <4A663DC7.4060600@kernel.org> <4A695897.2020902@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from hera.kernel.org ([140.211.167.34]:35344 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753051AbZHLG4H (ORCPT ); Wed, 12 Aug 2009 02:56:07 -0400 In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Yu, Fenghua" Cc: "Luck, Tony" , 'lkml' , "'linux-arch@vger.kernel.org'" , "'linux-ia64@vger.kernel.org'" Yu, Fenghua wrote: >> Yu, Fenghua wrote: >> >>> After cloning from >>> git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.git, kernel >>> built with CONFIG_DISCONTIGMEM=y boots ok. >>> >>> After pulling from review-ia64, kernel built with >>> CONFIG_DISCONTIGMEM=y can not boot on ia64. After loading kernel and >>> initrd, system hangs and doesn't show anything on serial port. >> Heh, I didn't really expect it to work that easily either. The code >> builds but is completely untested (I can't test them). Can you try to >> track it down? Serial console should be up and running at that point, >> no? >> >> Thanks. > > IA64 kernel boots hit this in mm/percpu.c > BUG_ON(ai->unit_size < size_sum); > ai->unit_size is PERCPU_PAGE_SIZE which is 64K on IA64. size_sum is > relatively smaller than 64K. > > Will you define PERCPU_DYNAMIC_RESERVE and PERCPU_MODULE_RESERVE as > PAGE_SIZE or the bigger one between the current definition and > PAGE_SIZE? Hmmm... * Is ai->reserved_size necessary for ia64? This is necessary if there's linking range restriction when loading modules. ai->reserved_size guarantees that all static module percpu variables are allocated in the first chunk which will be in the linear address range and very close to __per_cpu_start. If ai->reserved_size is not set, these areas are likely to end up high in the vmalloc area. For example, x86_64 assumes 32bit relocations should be enough to link module symbols and thus needs to set reserved_size but x86_32 can link to the whole 32bit space and thus can leave reserved_size at zero. * After determining the above, we can set ai->dyn_size to be ai->dyn_size = min(ai->unit_size - ai->static_size - ai->reserved_size, PERCPU_DYNAMIC_RESERVE); Would the above work? > Even with the above PAGE_SIZE changes, the kernel still reports > warning from 952: WARN_ON(chunk->immutable) and then panic. Hah... strange. Can you please attach full boot log? This is dicontig configuration, right? Thanks. -- tejun