Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965704AbbD0Wni (ORCPT ); Mon, 27 Apr 2015 18:43:38 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:40078 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965092AbbD0Wne (ORCPT ); Mon, 27 Apr 2015 18:43:34 -0400 Date: Mon, 27 Apr 2015 15:43:33 -0700 From: Andrew Morton To: Mel Gorman Cc: Linux-MM , Nathan Zimmer , Dave Hansen , Waiman Long , Scott Norton , Daniel J Blueman , LKML Subject: Re: [PATCH 05/13] mm: meminit: Make __early_pfn_to_nid SMP-safe and introduce meminit_pfn_in_nid Message-Id: <20150427154333.85a1fd2dbc38c7c0888fd4f5@linux-foundation.org> In-Reply-To: <1429785196-7668-6-git-send-email-mgorman@suse.de> References: <1429785196-7668-1-git-send-email-mgorman@suse.de> <1429785196-7668-6-git-send-email-mgorman@suse.de> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1578 Lines: 42 On Thu, 23 Apr 2015 11:33:08 +0100 Mel Gorman wrote: > __early_pfn_to_nid() in the generic and arch-specific implementations > use static variables to cache recent lookups. Without the cache > boot times are much higher due to the excessive memblock lookups but > it assumes that memory initialisation is single-threaded. Parallel > initialisation of struct pages will break that assumption so this patch > makes __early_pfn_to_nid() SMP-safe by requiring the caller to cache > recent search information. early_pfn_to_nid() keeps the same interface > but is only safe to use early in boot due to the use of a global static > variable. meminit_pfn_in_nid() is an SMP-safe version that callers must > maintain their own state for. Seems a bit awkward. > +struct __meminitdata mminit_pfnnid_cache global_init_state; > + > +/* Only safe to use early in boot when initialisation is single-threaded */ > int __meminit early_pfn_to_nid(unsigned long pfn) > { > int nid; > > - nid = __early_pfn_to_nid(pfn); > + /* The system will behave unpredictably otherwise */ > + BUG_ON(system_state != SYSTEM_BOOTING); Because of this. Providing a cache per cpu: struct __meminitdata mminit_pfnnid_cache global_init_state[NR_CPUS]; would be simpler? Also, `global_init_state' is a poor name for a kernel-wide symbol. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/