From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f69.google.com (mail-pl0-f69.google.com [209.85.160.69]) by kanga.kvack.org (Postfix) with ESMTP id 7D9A96B0010 for ; Tue, 27 Mar 2018 20:51:50 -0400 (EDT) Received: by mail-pl0-f69.google.com with SMTP id u1-v6so500455pls.16 for ; Tue, 27 Mar 2018 17:51:50 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id j21sor628650pfn.115.2018.03.27.17.51.49 for (Google Transport Security); Tue, 27 Mar 2018 17:51:49 -0700 (PDT) Date: Wed, 28 Mar 2018 08:51:42 +0800 From: Wei Yang Subject: Re: [PATCH] mm/page_alloc: break on the first hit of mem range Message-ID: <20180328005142.GC91956@WeideMacBook-Pro.local> Reply-To: Wei Yang References: <20180327035707.84113-1-richard.weiyang@gmail.com> <20180327154740.9a7713a74a383254b51f4d1a@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180327154740.9a7713a74a383254b51f4d1a@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Wei Yang , mhocko@suse.com, tj@kernel.org, linux-mm@kvack.org On Tue, Mar 27, 2018 at 03:47:40PM -0700, Andrew Morton wrote: >On Tue, 27 Mar 2018 11:57:07 +0800 Wei Yang wrote: > >> find_min_pfn_for_node() iterate on pfn range to find the minimum pfn for a >> node. The memblock_region in memblock_type are already ordered, which means >> the first hit in iteration is the minimum pfn. >> >> This patch returns the fist hit instead of iterating the whole regions. >> >> ... >> >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -6365,14 +6365,14 @@ unsigned long __init node_map_pfn_alignment(void) >> /* Find the lowest pfn for a node */ >> static unsigned long __init find_min_pfn_for_node(int nid) >> { >> - unsigned long min_pfn = ULONG_MAX; >> - unsigned long start_pfn; >> + unsigned long min_pfn; >> int i; >> >> - for_each_mem_pfn_range(i, nid, &start_pfn, NULL, NULL) >> - min_pfn = min(min_pfn, start_pfn); >> + for_each_mem_pfn_range(i, nid, &min_pfn, NULL, NULL) { >> + break; >> + } > >That would be the weirdest-looking code snippet in mm/! > You mean the only break in a for_each loop? Hmm..., this is really not that nice. Haven't noticed could get a "best" in this way :-) >Can't we just use a single and simple call to __next_mem_pfn_range(), >or something like that? > Sounds a better choice, if you like this version, I would rearrange the patch and send v2. Have a nice day~ >> >> ... >> -- Wei Yang Help you, Help me