From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E199BC282DD for ; Fri, 10 Jan 2020 15:20:17 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AB9292077C for ; Fri, 10 Jan 2020 15:20:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cVMdbMNE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AB9292077C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:47712 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ipw5A-0000sG-Ti for qemu-devel@archiver.kernel.org; Fri, 10 Jan 2020 10:20:16 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:33250) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ipw3J-0006m5-IA for qemu-devel@nongnu.org; Fri, 10 Jan 2020 10:18:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ipw3I-0003xv-4V for qemu-devel@nongnu.org; Fri, 10 Jan 2020 10:18:21 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:52441 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ipw3G-0003rw-Uq for qemu-devel@nongnu.org; Fri, 10 Jan 2020 10:18:20 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1578669498; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=R8COT8qa76Y4CXxhQhfrxopi6wrBWQ/T8rSjVi7aOWw=; b=cVMdbMNExsrs1KdTANr9At0gd5W66zVC0QzrPlILUcp3qeUIbq3wRbgbvT9z/J0qEFSfmh IgWvz/jYa3nstB5qdo6G9+/Niwp444klgtlAWO3Y+mZS5W5YhwiYUs60tojxXVo5QVybgL uVbP4mhiceztWjYZNQ312FvQ6+xiPHs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-357-sDfICJn6P12arHpOyxUcVQ-1; Fri, 10 Jan 2020 10:18:17 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1E15F800D48 for ; Fri, 10 Jan 2020 15:18:16 +0000 (UTC) Received: from redhat.com (ovpn-112-65.ams2.redhat.com [10.36.112.65]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 51C101001938; Fri, 10 Jan 2020 15:18:12 +0000 (UTC) Date: Fri, 10 Jan 2020 15:18:08 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Miklos Szeredi Subject: Re: [PATCH 068/104] virtiofsd: passthrough_ll: control readdirplus Message-ID: <20200110151808.GT3423494@redhat.com> References: <20191212163904.159893-1-dgilbert@redhat.com> <20191212163904.159893-69-dgilbert@redhat.com> <20200107112316.GL3368802@redhat.com> <20200110150447.GH3901@work-vm> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: sDfICJn6P12arHpOyxUcVQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Vivek Goyal , "Dr. David Alan Gilbert" , Stefan Hajnoczi , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Jan 10, 2020 at 04:13:08PM +0100, Miklos Szeredi wrote: > On Fri, Jan 10, 2020 at 4:04 PM Dr. David Alan Gilbert > wrote: > > > > * Daniel P. Berrang=C3=A9 (berrange@redhat.com) wrote: > > > On Thu, Dec 12, 2019 at 04:38:28PM +0000, Dr. David Alan Gilbert (git= ) wrote: > > > > From: Miklos Szeredi > > > > > > > > > > What is readdirplus and what do we need a command line option to > > > control it ? What's the user benefit of changing the setting ? > > > > cc'ing Miklos who understands this better than me. > > > > My understanding is that readdirplus is a heuristic inherited from NFS > > where when you iterate over the directory you also pick up stat() data > > for each entry in the directory. You then cache that stat data > > somewhere. > > The Plus-ness is that a lot of directory operations involve you stating > > each entry (e.g. to figure out if you can access it etc) so rolling it > > into one op avoids the separate stat. The unplus-ness is that it's an > > overhead and I think changes some of the caching behaviour. >=20 > Yeah, so either may give better performance and it's hard to pick a > clear winner. NFS also has an option to control this. IIUC from the man page, the NFS option for controlling this is a client side mount option. This makes sense as only the client really has knowledge of whether its workload will benefit. With this in mind, should the readdirplus control for virtio-fs also be a guest mount option instead of a host virtiofsd CLI option ? The guest admin seems best placed to know whether their workload will benefit or not. Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberrange= :| |: https://libvirt.org -o- https://fstop138.berrange.com= :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange= :|