Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933141AbcDYQmg (ORCPT ); Mon, 25 Apr 2016 12:42:36 -0400 Received: from zimbra13.linbit.com ([212.69.166.240]:46258 "EHLO zimbra13.linbit.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933062AbcDYQmf (ORCPT ); Mon, 25 Apr 2016 12:42:35 -0400 From: Philipp Reisner To: Bart Van Assche Cc: Jens Axboe , "linux-kernel@vger.kernel.org" , "drbd-dev@lists.linbit.com" Subject: Re: [Drbd-dev] [PATCH 04/30] drbd: Implement handling of thinly provisioned storage on resync target nodes Date: Mon, 25 Apr 2016 11:21:13 -0500 Message-ID: <85987419.JuPsLEWddI@phil-dell-xps.local> User-Agent: KMail/4.13.3 (Linux/3.13.0-55-generic; KDE/4.13.3; x86_64; ; ) In-Reply-To: <571E37AD.1050607@sandisk.com> References: <1461586077-11581-1-git-send-email-philipp.reisner@linbit.com> <1461586077-11581-5-git-send-email-philipp.reisner@linbit.com> <571E37AD.1050607@sandisk.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 835 Lines: 23 Am Montag, 25. April 2016, 08:28:45 schrieb Bart Van Assche: > On 04/25/2016 05:10 AM, Philipp Reisner wrote: > > If during resync we read only zeroes for a range of sectors assume > > that these secotors can be discarded on the sync target node. > > Hello Phil, > > With which interconnect(s) has this patch been tested? I'm afraid that > for high-speed interconnects this patch will slow down I/O instead of > making it faster because all_zero() examines all data before it is sent. > Hi Bart, that it might make things slower is true for sure. The benefit it provides is to de-allocate blocks on the secondary obviously. The whole feature is optional and it is off by default. Obviously we want to have a generic interface like SEEK_HOLE/ SEEK_DATA for block devices, but that does not exist as of today. best regards, Phil