Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751986Ab3HTIJo (ORCPT ); Tue, 20 Aug 2013 04:09:44 -0400 Received: from mail-ee0-f44.google.com ([74.125.83.44]:35727 "EHLO mail-ee0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751451Ab3HTIJP (ORCPT ); Tue, 20 Aug 2013 04:09:15 -0400 Date: Tue, 20 Aug 2013 10:09:10 +0200 From: Ingo Molnar To: Stanislaw Gruszka Cc: Mike Snitzer , dm-devel@redhat.com, linux-kernel@vger.kernel.org, Mikulas Patocka , Frederic Weisbecker Subject: Re: [PATCH 1/2] Revert "Revert "math64: New div64_u64_rem helper"" Message-ID: <20130820080910.GA11072@gmail.com> References: <1376078164-23147-1-git-send-email-snitzer@redhat.com> <20130820070045.GA1665@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130820070045.GA1665@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 972 Lines: 32 * Stanislaw Gruszka wrote: > On Fri, Aug 09, 2013 at 03:56:03PM -0400, Mike Snitzer wrote: > > This reverts commit f3002134158092178be81339ec5a22ff80e6c308. > > > > div64_u64_rem was removed because there were no other users. > > > > But Device Mapper's I/O statistics support has a need for > > div64_u64_rem; reintroduce this helper. > > This slows down div64_u64 operation, especially on 32-bit > systems. > > Since dm statistic code is possibly not performance > critical perhaps you could use something like below > instead to calculate remainder: > > res = div64_u64(a, b); > rem = a - b*res; Or introduce a separately named helper without touching the existing methods. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/