From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f182.google.com ([209.85.216.182]:33049 "EHLO mail-qt0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750806AbdAXRuZ (ORCPT ); Tue, 24 Jan 2017 12:50:25 -0500 Received: by mail-qt0-f182.google.com with SMTP id v23so195579902qtb.0 for ; Tue, 24 Jan 2017 09:50:24 -0800 (PST) Message-ID: <1485280222.3143.25.camel@redhat.com> Subject: Re: regression in DIO write behavior From: Jeff Layton To: Weston Andros Adamson Cc: linux-nfs list , Scott Mayhew Date: Tue, 24 Jan 2017 12:50:22 -0500 In-Reply-To: <963DBD29-C835-4716-9EAE-74C2EACA427F@monkey.org> References: <1485272659.3143.18.camel@redhat.com> <963DBD29-C835-4716-9EAE-74C2EACA427F@monkey.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org List-ID: On Tue, 2017-01-24 at 12:23 -0500, Weston Andros Adamson wrote: > Hey Jeff, > > That sounds like a regression to me. I don't think it's been around since the > pgio rework, but maybe? > > -dros > I certainly could be wrong. :) I did open this bug, and we'll track it down there: https://bugzilla.redhat.com/show_bug.cgi?id=1416127 Looks like Scott bisected it down in RHEL7 kernels so we should be able to ID it from there. Cheers, Jeff > > On Jan 24, 2017, at 10:44 AM, Jeff Layton wrote: > > > > I've noticed a probable regression in recent kernels. When you run the > > attached program on an older kernel (I used 2.6.32-642.6.2.el6.x86_64), > > I see the kernel generate wsize WRITE calls on the wire. > > > > When I run the same program on a more modern kernel (mainline as of > > today), it generates a ton of page-sized I/Os instead. I've verified > > that iov_iter_get_pages_alloc is returning a wsize array of pages, it > > just seems like the request handling code isn't stitching them together > > like it should. > > > > Is this an expected change or a regression? I'm guessing the latter, and > > that it might have crept in during the pageio rework from a couple of > > years ago. > > > > Any idea where the bug might be? > > -- > > Jeff Layton > > -- Jeff Layton