From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx112.postini.com [74.125.245.112]) by kanga.kvack.org (Postfix) with SMTP id 4D0886B0032 for ; Tue, 3 Sep 2013 22:07:07 -0400 (EDT) Message-ID: <5226957F.2060704@cn.fujitsu.com> Date: Wed, 04 Sep 2013 10:05:51 +0800 From: Tang Chen MIME-Version: 1.0 Subject: Re: [PATCH 07/11] x86, memblock: Set lowest limit for memblock_alloc_base_nid(). References: <1377596268-31552-1-git-send-email-tangchen@cn.fujitsu.com> <1377596268-31552-8-git-send-email-tangchen@cn.fujitsu.com> <1378255041.10300.931.camel@misato.fc.hp.com> In-Reply-To: <1378255041.10300.931.camel@misato.fc.hp.com> Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8; format=flowed Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani Cc: rjw@sisk.pl, lenb@kernel.org, tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com, akpm@linux-foundation.org, tj@kernel.org, trenn@suse.de, yinghai@kernel.org, jiang.liu@huawei.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, mgorman@suse.de, minchan@kernel.org, mina86@mina86.com, gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com, lwoodman@redhat.com, riel@redhat.com, jweiner@redhat.com, prarit@redhat.com, zhangyanfei@cn.fujitsu.com, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-acpi@vger.kernel.org On 09/04/2013 08:37 AM, Toshi Kani wrote: > On Tue, 2013-08-27 at 17:37 +0800, Tang Chen wrote: >> memblock_alloc_base_nid() is a common API of memblock. And it calls >> memblock_find_in_range_node() with %start = 0, which means it has no >> limit for the lowest address by default. >> >> memblock_find_in_range_node(0, max_addr, size, align, nid); >> >> Since we introduced current_limit_low to memblock, if we have no limit >> for the lowest address or we are not sure, we should pass >> MEMBLOCK_ALLOC_ACCESSIBLE to %start so that it will be limited by the >> default low limit. >> >> dma_contiguous_reserve() and setup_log_buf() will eventually call >> memblock_alloc_base_nid() to allocate memory. So if the allocation order >> is from low to high, they will allocate memory from the lowest limit >> to higher memory. > > This requires the callers to use MEMBLOCK_ALLOC_ACCESSIBLE instead of 0. > Is there a good way to make sure that all callers will follow this rule > going forward? Perhaps, memblock_find_in_range_node() should emit some > message if 0 is passed when current_order is low to high and the boot > option is specified? How about set this as the default rule: When using from low to high order, always allocate memory from current_limit_low. So far, I think only movablenode boot option will use this order. > > Similarly, I wonder if we should have a check to the allocation size to > make sure that all allocations will stay small in this case. > We can check the size. But what is the stragety after we found that the size is too large ? Do we refuse to allocate memory ? I don't think so. I think only relocate_initrd() and reserve_crachkernel() could allocate large memory. reserve_crachkernel() is easy to reorder, but reordering relocate_initrd() is difficult because acpi_initrd_override() need to access to it with va. I think on most servers, we don't need to do relocate_initrd(). initrd will be loaded to mapped memory in normal situation. Can we just leave it there ? Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org