From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:46559) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hErbv-0008Pl-PZ for qemu-devel@nongnu.org; Fri, 12 Apr 2019 04:32:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hErbu-0001lX-VN for qemu-devel@nongnu.org; Fri, 12 Apr 2019 04:32:35 -0400 Received: from mx2.suse.de ([195.135.220.15]:36382 helo=mx1.suse.de) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hErbu-0001iP-Mz for qemu-devel@nongnu.org; Fri, 12 Apr 2019 04:32:34 -0400 Date: Fri, 12 Apr 2019 10:32:30 +0200 From: Jan Kara Message-ID: <20190412083230.GA29850@quack2.suse.cz> References: <20190410040826.24371-1-pagupta@redhat.com> <20190410040826.24371-2-pagupta@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH v5 1/6] libnvdimm: nd_region flush callback support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Dan Williams Cc: Pankaj Gupta , linux-nvdimm , Linux Kernel Mailing List , virtualization@lists.linux-foundation.org, KVM list , linux-fsdevel , Linux ACPI , Qemu Developers , linux-ext4 , linux-xfs , Ross Zwisler , Vishal L Verma , Dave Jiang , "Michael S. Tsirkin" , Jason Wang , Matthew Wilcox , "Rafael J. Wysocki" , Christoph Hellwig , Len Brown , Jan Kara , Theodore Ts'o , Andreas Dilger , "Darrick J. Wong" , lcapitulino@redhat.com, Kevin Wolf , Igor Mammedov , jmoyer , Nitesh Narayan Lal , Rik van Riel , Stefan Hajnoczi , Andrea Arcangeli , David Hildenbrand , david , cohuck@redhat.com, Xiao Guangrong , Paolo Bonzini , kilobyte@angband.pl, yuval.shaia@oracle.com On Thu 11-04-19 07:51:48, Dan Williams wrote: > On Tue, Apr 9, 2019 at 9:09 PM Pankaj Gupta wrote: > > + } else { > > + if (nd_region->flush(nd_region)) > > + rc = -EIO; > > Given the common case wants to be fast and synchronous I think we > should try to avoid retpoline overhead by default. So something like > this: > > if (nd_region->flush == generic_nvdimm_flush) > rc = generic_nvdimm_flush(...); I'd either add a comment about avoiding retpoline overhead here or just make ->flush == NULL mean generic_nvdimm_flush(). Just so that people don't get confused by the code. Honza -- Jan Kara SUSE Labs, CR From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2113BC10F0E for ; Fri, 12 Apr 2019 08:33:30 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E04E92084D for ; Fri, 12 Apr 2019 08:33:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E04E92084D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:60830 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hErcn-0000ZL-0o for qemu-devel@archiver.kernel.org; Fri, 12 Apr 2019 04:33:29 -0400 Received: from eggs.gnu.org ([209.51.188.92]:46559) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hErbv-0008Pl-PZ for qemu-devel@nongnu.org; Fri, 12 Apr 2019 04:32:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hErbu-0001lX-VN for qemu-devel@nongnu.org; Fri, 12 Apr 2019 04:32:35 -0400 Received: from mx2.suse.de ([195.135.220.15]:36382 helo=mx1.suse.de) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hErbu-0001iP-Mz for qemu-devel@nongnu.org; Fri, 12 Apr 2019 04:32:34 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A5FDCAECB; Fri, 12 Apr 2019 08:32:31 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id EBF6F1E429B; Fri, 12 Apr 2019 10:32:30 +0200 (CEST) Date: Fri, 12 Apr 2019 10:32:30 +0200 From: Jan Kara To: Dan Williams Message-ID: <20190412083230.GA29850@quack2.suse.cz> References: <20190410040826.24371-1-pagupta@redhat.com> <20190410040826.24371-2-pagupta@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x (no timestamps) [generic] X-Received-From: 195.135.220.15 Subject: Re: [Qemu-devel] [PATCH v5 1/6] libnvdimm: nd_region flush callback support X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Pankaj Gupta , cohuck@redhat.com, Jan Kara , KVM list , "Michael S. Tsirkin" , Jason Wang , david , Qemu Developers , virtualization@lists.linux-foundation.org, Andreas Dilger , Ross Zwisler , Andrea Arcangeli , Dave Jiang , linux-nvdimm , Vishal L Verma , David Hildenbrand , Matthew Wilcox , Christoph Hellwig , Linux ACPI , jmoyer , linux-ext4 , Len Brown , kilobyte@angband.pl, Rik van Riel , yuval.shaia@oracle.com, Stefan Hajnoczi , Paolo Bonzini , lcapitulino@redhat.com, Kevin Wolf , Nitesh Narayan Lal , Theodore Ts'o , Xiao Guangrong , "Darrick J. Wong" , "Rafael J. Wysocki" , Linux Kernel Mailing List , linux-xfs , linux-fsdevel , Igor Mammedov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190412083230.rP9V6oljVIc8T3je9igfRS34sfWcDGz4UY24Q6lLHiQ@z> On Thu 11-04-19 07:51:48, Dan Williams wrote: > On Tue, Apr 9, 2019 at 9:09 PM Pankaj Gupta wrote: > > + } else { > > + if (nd_region->flush(nd_region)) > > + rc = -EIO; > > Given the common case wants to be fast and synchronous I think we > should try to avoid retpoline overhead by default. So something like > this: > > if (nd_region->flush == generic_nvdimm_flush) > rc = generic_nvdimm_flush(...); I'd either add a comment about avoiding retpoline overhead here or just make ->flush == NULL mean generic_nvdimm_flush(). Just so that people don't get confused by the code. Honza -- Jan Kara SUSE Labs, CR