Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756351AbbGVM4z (ORCPT ); Wed, 22 Jul 2015 08:56:55 -0400 Received: from mga14.intel.com ([192.55.52.115]:59558 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751756AbbGVM4y (ORCPT ); Wed, 22 Jul 2015 08:56:54 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,523,1432623600"; d="scan'208";a="610718007" Message-ID: <55AF9286.1020507@intel.com> Date: Wed, 22 Jul 2015 20:54:30 +0800 From: Pan Xinhui User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Borislav Petkov CC: "linux-kernel@vger.kernel.org" , Thomas Gleixner , mingo@redhat.com, hpa@zytor.com, x86@kernel.org, bp@suse.de, toshi.kani@hp.com, jgross@suse.com, mcgrof@suse.com, "mnipxh@163.com" , "yanmin_zhang@linux.intel.com" Subject: Re: [PATCH V3] x86/mm/pat: Do a small optimization and fix in reserve_memtype References: <55AF2C68.5010304@intel.com> <20150722074649.GD7979@nazgul.tnic> <55AF5CFC.1080303@intel.com> <20150722104624.GA26553@nazgul.tnic> In-Reply-To: <20150722104624.GA26553@nazgul.tnic> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2363 Lines: 75 hi, Borislav thanks for your reply. :) On 2015年07月22日 18:46, Borislav Petkov wrote: > On Wed, Jul 22, 2015 at 05:06:04PM +0800, Pan Xinhui wrote: >> how about: >> memtype_lock protects the rb-tree root and the rb-nodes which is a field of memtype from delete/add/lookup in a race. > > Use this: > > "All pat_rbtree operations need to be performed while holding the > memtype_lock." > thanks! >> Actually I have same questions. I find these output logs are added in >> commit: 6997ab4982a29925e79f72c3a59823cf944c3529(x86: add PAT related >> debug prints) In the past, *new_type == actual_type == new->type on >> success. codes are below. author use actual_type there. > > So this function is one bit PITA. So req_type is used to compute actual > type a bit higher: > > actual_type = pat_x_mtrr_type(start, end, req_type); > > and from then on actual_type is being used. > > BUT!, in order to have *all* debugging information, the last dprintk() agree, output all debugging information. > call should dump actual_type and req_type because this way we show what then why not append "act %s" to the dprintk format string? > pat_x_mtrr_type() did too. And we don't need to dump new->type because > this is the !err case and in that case we assigned new_type to it, which > we dump already. yes, new->type is same with *new_type, and dump same value twice. > > Ok? > Let me think for a while. I wonder why there is not any comment that could tell developers what "track %s" mean. In different places of this file, "track %s" can mean what type of memory it is now, or it used to be. So I think this output filed "track %s" is just whatever people want to need to print out. I prefer to dump all debugging information here, so I agree with your idea. thanks > Btw, you could also simplify this: > > if (is_range_ram == 1) { > > err = reserve_ram_pages_type(start, end, req_type, new_type); > > return err; > } > > to: > > if (is_range_ram == 1) > return reserve_ram_pages_type(start, end, req_type, new_type); > seems better now, thanks! > while at it. > > Thanks. > thanks xinhui -- 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/