From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) (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 5122421196236 for ; Wed, 5 Dec 2018 12:42:50 -0800 (PST) Date: Wed, 5 Dec 2018 21:42:47 +0100 From: Michal Hocko Subject: Re: [mm PATCH v6 6/7] mm: Add reserved flag setting to set_page_links Message-ID: <20181205204247.GY1286@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> <19c9f0fe83a857d5858c386a08ca2ddeba7cf27b.camel@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <19c9f0fe83a857d5858c386a08ca2ddeba7cf27b.camel@linux.intel.com> 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: Alexander Duyck 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 05-12-18 09:55:17, Alexander Duyck wrote: > 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. >>From my experience Andrew can drop patches between different versions of the patchset. Things can change a lot while they are in mmotm and under the discussion. -- Michal Hocko SUSE Labs _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm