From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753627AbdEJPVO (ORCPT ); Wed, 10 May 2017 11:21:14 -0400 Received: from shards.monkeyblade.net ([184.105.139.130]:41172 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753465AbdEJPVG (ORCPT ); Wed, 10 May 2017 11:21:06 -0400 Date: Wed, 10 May 2017 11:20:59 -0400 (EDT) Message-Id: <20170510.112059.169845404310247896.davem@davemloft.net> To: pasha.tatashin@oracle.com Cc: mhocko@kernel.org, linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, heiko.carstens@de.ibm.com Subject: Re: [v3 0/9] parallelized "struct page" zeroing From: David Miller In-Reply-To: References: <3f5f1416-aa91-a2ff-cc89-b97fcaa3e4db@oracle.com> <20170510145726.GM31466@dhcp22.suse.cz> X-Mailer: Mew version 6.7 on Emacs 24.5 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 10 May 2017 07:39:32 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Pasha Tatashin Date: Wed, 10 May 2017 11:01:40 -0400 > Perhaps you are right, and I will measure on x86. But, I suspect hit > can become unacceptable on some platfoms: there is an overhead of > calling a function, even if it is leaf-optimized, and there is an > overhead in memset() to check for alignments of size and address, > types of setting (zeroing vs. non-zeroing), etc., that adds up > quickly. Another source of overhead on the sparc64 side is that we much do memory barriers around the block initializiing stores. So batching calls to memset() amortize that as well.