From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 6C8F22117D76B for ; Wed, 5 Dec 2018 09:55:17 -0800 (PST) Message-ID: <19c9f0fe83a857d5858c386a08ca2ddeba7cf27b.camel@linux.intel.com> Subject: Re: [mm PATCH v6 6/7] mm: Add reserved flag setting to set_page_links From: Alexander Duyck Date: Wed, 05 Dec 2018 09:55:17 -0800 In-Reply-To: <20181205172225.GT1286@dhcp22.suse.cz> References: <154361452447.7497.1348692079883153517.stgit@ahduyck-desk1.amr.corp.intel.com> <154361479877.7497.2824031260670152276.stgit@ahduyck-desk1.amr.corp.intel.com> <20181205172225.GT1286@dhcp22.suse.cz> Mime-Version: 1.0 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Michal Hocko Cc: pavel.tatashin@microsoft.com, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, willy@infradead.org, mingo@kernel.org, linux-mm@kvack.org, khalid.aziz@oracle.com, rppt@linux.vnet.ibm.com, vbabka@suse.cz, sparclinux@vger.kernel.org, akpm@linux-foundation.org, ldufour@linux.vnet.ibm.com, mgorman@techsingularity.net, davem@davemloft.net, kirill.shutemov@linux.intel.com List-ID: On Wed, 2018-12-05 at 18:22 +0100, Michal Hocko wrote: > On Fri 30-11-18 13:53:18, Alexander Duyck wrote: > > Modify the set_page_links function to include the setting of the reserved > > flag via a simple AND and OR operation. The motivation for this is the fact > > that the existing __set_bit call still seems to have effects on performance > > as replacing the call with the AND and OR can reduce initialization time. > > > > Looking over the assembly code before and after the change the main > > difference between the two is that the reserved bit is stored in a value > > that is generated outside of the main initialization loop and is then > > written with the other flags field values in one write to the page->flags > > value. Previously the generated value was written and then then a btsq > > instruction was issued. > > > > On my x86_64 test system with 3TB of persistent memory per node I saw the > > persistent memory initialization time on average drop from 23.49s to > > 19.12s per node. > > I have tried to explain why the whole reserved bit doesn't make much > sense in this code several times already. You keep ignoring that and > that is highly annoying. Especially when you add a tricky code to > optimize something that is not really needed. > > Based on that I am not going to waste my time on other patches in this > series to review and give feedback which might be ignored again. I got your explanation. However Andrew had already applied the patches and I had some outstanding issues in them that needed to be addressed. So I thought it best to send out this set of patches with those fixes before the code in mm became too stale. I am still working on what to do about the Reserved bit, and plan to submit it as a follow-up set. _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm