From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f49.google.com (mail-pa0-f49.google.com [209.85.220.49]) by kanga.kvack.org (Postfix) with ESMTP id 70D9C6B0034 for ; Mon, 23 Sep 2013 13:08:57 -0400 (EDT) Received: by mail-pa0-f49.google.com with SMTP id ld10so3801289pab.8 for ; Mon, 23 Sep 2013 10:08:57 -0700 (PDT) Received: by mail-pa0-f53.google.com with SMTP id kq14so2533591pab.12 for ; Mon, 23 Sep 2013 09:44:23 -0700 (PDT) Message-ID: <52406FD2.9020501@gmail.com> Date: Tue, 24 Sep 2013 00:44:02 +0800 From: Zhang Yanfei MIME-Version: 1.0 Subject: Re: [PATCH v3 2/5] memblock: Improve memblock to support allocation from lower address. References: <1379064655-20874-1-git-send-email-tangchen@cn.fujitsu.com> <1379064655-20874-3-git-send-email-tangchen@cn.fujitsu.com> <20130923155027.GD14547@htj.dyndns.org> In-Reply-To: <20130923155027.GD14547@htj.dyndns.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Tang Chen , rjw@sisk.pl, lenb@kernel.org, tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com, akpm@linux-foundation.org, toshi.kani@hp.com, zhangyanfei@cn.fujitsu.com, liwanp@linux.vnet.ibm.com, 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, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-acpi@vger.kernel.org Hello tejun, On 09/23/2013 11:50 PM, Tejun Heo wrote: > Hello, > > Please separate out factoring out of top-down allocation. That change > is an equivalent conversion which shouldn't involve any functional > difference. Mixing that with introduction of new feature isn't a good > idea, so the patch split should be 1. split out top-down allocation > from memblock_find_in_range_node() 2. introduce bottom-up flag and > implement the feature. Ok, will do the split. > > On Fri, Sep 13, 2013 at 05:30:52PM +0800, Tang Chen wrote: >> +/** >> * memblock_find_in_range_node - find free area in given range and node >> - * @start: start of candidate range >> + * @start: start of candidate range, can be %MEMBLOCK_ALLOC_ACCESSIBLE > > The only reason @end has special ACCESSIBLE flag is because we don't > know how high is actually accessible and it needs to be distinguished > from ANYWHERE. We assume that the lower addresses are always mapped, > so using ACCESSIBLE for @start is weird. I think it'd be clearer to > make the memblock interface to set the direction explicitly state what > it's doing - ie. something like set_memblock_alloc_above_kernel(bool > enable). We clearly don't want pure bottom-up allocation and the > @start/@end params in memblock interface are used to impose extra > limitations for each allocation, not the overall allocator behavior. > >> @@ -100,8 +180,7 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t start, >> phys_addr_t end, phys_addr_t size, >> phys_addr_t align, int nid) >> { >> - phys_addr_t this_start, this_end, cand; >> - u64 i; >> + phys_addr_t ret; >> >> /* pump up @end */ >> if (end == MEMBLOCK_ALLOC_ACCESSIBLE) >> @@ -111,18 +190,22 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t start, >> start = max_t(phys_addr_t, start, PAGE_SIZE); >> end = max(start, end); >> >> - for_each_free_mem_range_reverse(i, nid, &this_start, &this_end, NULL) { >> - this_start = clamp(this_start, start, end); >> - this_end = clamp(this_end, start, end); >> + if (memblock_direction_bottom_up()) { >> + /* >> + * MEMBLOCK_ALLOC_ACCESSIBLE is 0, which is less than the end >> + * of kernel image. So callers specify MEMBLOCK_ALLOC_ACCESSIBLE >> + * as @start is OK. >> + */ >> + start = max(start, __pa_symbol(_end)); /* End of kernel image. */ >> >> - if (this_end < size) >> - continue; >> + ret = __memblock_find_range(start, end, size, align, nid); >> + if (ret) >> + return ret; >> >> - cand = round_down(this_end - size, align); >> - if (cand >= this_start) >> - return cand; >> + pr_warn("memblock: Failed to allocate memory in bottom up direction. Now try top down direction.\n"); > > You probably wanna explain why retrying top-down allocation may > succeed when bottom-up failed. ok. The reason is we always limit bottom-up allocation from the kernel image end, but to-down allocation doesn't have the limit, so retrying top-down allocation may succeed when bottom-up failed. Will add the comment to explain the retry. Thanks. > > Thanks. > -- Thanks. Zhang Yanfei -- 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