From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx135.postini.com [74.125.245.135]) by kanga.kvack.org (Postfix) with SMTP id C84D26B0031 for ; Wed, 4 Sep 2013 11:24:00 -0400 (EDT) Message-ID: <1378308138.10300.948.camel@misato.fc.hp.com> Subject: Re: [PATCH 07/11] x86, memblock: Set lowest limit for memblock_alloc_base_nid(). From: Toshi Kani Date: Wed, 04 Sep 2013 09:22:18 -0600 In-Reply-To: <5226957F.2060704@cn.fujitsu.com> 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> <5226957F.2060704@cn.fujitsu.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tang Chen 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 Wed, 2013-09-04 at 10:05 +0800, Tang Chen wrote: > 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. Sounds good to me. > > 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. We can just add a log message. No need to fail. > 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 ? Since this approach relies on the assumption that all allocations are small enough, it would be nice to have a way to verify if it remains true. How about we measure a total amount of allocations while the order is low to high, and log it when switched to high to low? This way, we can easily monitor the usage. Thanks, -Toshi -- 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