Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752586AbaLEITD (ORCPT ); Fri, 5 Dec 2014 03:19:03 -0500 Received: from mail1.SerNet.de ([193.175.80.2]:55312 "EHLO mail.SerNet.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752237AbaLEIS7 (ORCPT ); Fri, 5 Dec 2014 03:18:59 -0500 Date: Fri, 5 Dec 2014 09:17:54 +0100 From: Volker Lendecke To: Andrew Morton Cc: Milosz Tanski , LKML , Christoph Hellwig , "linux-fsdevel@vger.kernel.org" , "linux-aio@kvack.org" , Mel Gorman , Tejun Heo , Jeff Moyer , "Theodore Ts'o" , Al Viro , Linux API , Michael Kerrisk , linux-arch@vger.kernel.org Subject: Re: [PATCH v6 0/7] vfs: Non-blockling buffered fs read (page cache only) Reply-To: Volker.Lendecke@SerNet.DE References: <20141125150101.9596a09e.akpm@linux-foundation.org> <20141202144200.a4ca81a46a43563a8874fd8e@linux-foundation.org> <20141204151102.2d7e11dca39f130c2dff2294@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20141204151102.2d7e11dca39f130c2dff2294@linux-foundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) Message-Id: Organization: SerNet GmbH, Goettingen, Germany Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 04, 2014 at 03:11:02PM -0800, Andrew Morton wrote: > I can see all that, but it's handwaving. Yes, preadv2() will perform > better in some circumstances than fincore+pread. But how much better? > Enough to justify this approach, or not? > > Alas, the only way to really settle that is to implement fincore() and > to subject it to a decent amount of realistic quantitative testing. > > Ho hum. > > Could you please hunt down some libuv developers, see if we can solicit > some quality input from them? As I said, we really don't want to merge > this then find that people don't use it for some reason, or that it > needs changes. All I can say from a Samba perspective is that none of the ARM based Storage boxes I have seen so far do AIO because of the base footprint for every read. For sequential reads kernel-level readahead could kick in properly and we should be able to give them the best of both worlds: No context switches in the default case but also good parallel behaviour for other workloads. The most important benchmark for those guys is to read a DVD image, whether it makes sense or not. Volker -- SerNet GmbH, Bahnhofsallee 1b, 37081 G?ttingen phone: +49-551-370000-0, fax: +49-551-370000-9 AG G?ttingen, HRB 2816, GF: Dr. Johannes Loxen http://www.sernet.de, mailto:kontakt@sernet.de -- 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/