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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49170C433F5 for ; Fri, 12 Nov 2021 10:27:49 +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 E6A5760E53 for ; Fri, 12 Nov 2021 10:27:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org E6A5760E53 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:55596 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mlTmd-0001Oi-WE for qemu-devel@archiver.kernel.org; Fri, 12 Nov 2021 05:27:48 -0500 Received: from eggs.gnu.org ([209.51.188.92]:58514) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mlTln-0000bD-Sx for qemu-devel@nongnu.org; Fri, 12 Nov 2021 05:26:55 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:51446) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mlTll-0001Ny-QV for qemu-devel@nongnu.org; Fri, 12 Nov 2021 05:26:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1636712812; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=U6e25+e/ZSCpcmDEgbTlxOqGGT5nX7DPRYKkPEyxua8=; b=PiyS7TthDKaczSdqBZh9C12HTC7QR7OX2wNhvZM25x5849W/PDTC+LEcSOPPldN2Cgo8ME yT1m5WoczCJvPm5YnoqjANqF+CPxUS9evdp8cFpXV7l5xOjxtcF1vXKXE2yS2NkbQcNsWW Ts2eb7n0jYO7N+AfISCUbENRed/87l8= 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-595--pK8AsSbPYO2OD_eYvX7sw-1; Fri, 12 Nov 2021 05:26:48 -0500 X-MC-Unique: -pK8AsSbPYO2OD_eYvX7sw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 36CCBE757 for ; Fri, 12 Nov 2021 10:26:47 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.12]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 07F27179B3; Fri, 12 Nov 2021 10:26:41 +0000 (UTC) Date: Fri, 12 Nov 2021 10:26:38 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Leonardo Bras , qemu-devel@nongnu.org, Markus Armbruster , Eric Blake , "Dr. David Alan Gilbert" , Juan Quintela Subject: Re: [PATCH v5 1/6] QIOChannel: Add io_writev_zerocopy & io_flush_zerocopy callbacks Message-ID: References: <20211112051040.923746-1-leobras@redhat.com> <20211112051040.923746-2-leobras@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.699, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Nov 12, 2021 at 10:13:01AM +0000, Daniel P. Berrangé wrote: > On Fri, Nov 12, 2021 at 02:10:36AM -0300, Leonardo Bras wrote: > > Adds io_writev_zerocopy and io_flush_zerocopy as optional callback to QIOChannelClass, > > allowing the implementation of zerocopy writes by subclasses. > > > > How to use them: > > - Write data using qio_channel_writev_zerocopy(), > > - Wait write completion with qio_channel_flush_zerocopy(). > > > > Notes: > > As some zerocopy implementations work asynchronously, it's > > recommended to keep the write buffer untouched until the return of > > qio_channel_flush_zerocopy(), to avoid the risk of sending an updated > > buffer instead of the one at the write. > > > > As the new callbacks are optional, if a subclass does not implement them, then: > > - io_writev_zerocopy will return -1, > > - io_flush_zerocopy will return 0 without changing anything. > > > > Also, some functions like qio_channel_writev_full_all() were adapted to > > receive a flag parameter. That allows shared code between zerocopy and > > non-zerocopy writev. > > > > Signed-off-by: Leonardo Bras > > --- > > include/io/channel.h | 93 ++++++++++++++++++++++++++++++++++++++------ > > io/channel.c | 65 +++++++++++++++++++++++++------ > > 2 files changed, 135 insertions(+), 23 deletions(-) > > > > diff --git a/include/io/channel.h b/include/io/channel.h > > index 88988979f8..a19c09bb84 100644 > > --- a/include/io/channel.h > > +++ b/include/io/channel.h > > +/** > > + * qio_channel_writev_zerocopy: > > + * @ioc: the channel object > > + * @iov: the array of memory regions to write data from > > + * @niov: the length of the @iov array > > + * @errp: pointer to a NULL-initialized error object > > + * > > + * Behaves like qio_channel_writev_full_all_flags, but may write > > qio_channel_writev > > > + * data asynchronously while avoiding unnecessary data copy. > > + * This function may return before any data is actually written, > > + * but should queue every buffer for writing. > > Callers mustn't rely on "should" docs - they must rely on the > return value indicating how many bytes were accepted. Also mention that this requires locked memory and can/will fail if insufficient locked memory is available. Regards, Daniel -- |: 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 :|