From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751056Ab3HSRyL (ORCPT ); Mon, 19 Aug 2013 13:54:11 -0400 Received: from mail-pb0-f49.google.com ([209.85.160.49]:33865 "EHLO mail-pb0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750898Ab3HSRyJ (ORCPT ); Mon, 19 Aug 2013 13:54:09 -0400 Message-ID: <1376934845.24869.43.camel@bobble.lax.corp.google.com> Subject: Re: [dm-devel] dm: Make MIN_IOS, et al, tunable via sysctl. From: Frank Mayhar To: device-mapper development Cc: linux-kernel@vger.kernel.org Date: Mon, 19 Aug 2013 10:54:05 -0700 In-Reply-To: <20130819140016.GB27167@redhat.com> References: <1376070533.26057.244.camel@bobble.lax.corp.google.com> <20130819140016.GB27167@redhat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2013-08-19 at 10:00 -0400, Mike Snitzer wrote: > Performance isn't the concern. The concern is: does DM allow for > forward progress if the system's memory is completely exhausted? > > This is why request-based has such an extensive reserve, because it > needs to account for cloning the largest possible request that comes in > (with multiple bios). Thanks for the response. In our particular case, I/O will be file system based and over a network, which makes it pretty easy for us to be sure that large I/Os never happen. That notwithstanding, however, as you said it just seems reasonable to make these values configurable. I'm also looking at making some similar constants in dm-verity and dm-bufio configurable in the same way and for similar reasons. -- Frank Mayhar 310-460-4042