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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 4685BEA854E for ; Tue, 10 Mar 2026 08:53:50 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vzspn-00054H-PG; Tue, 10 Mar 2026 04:53:01 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vzspk-000541-R6 for qemu-devel@nongnu.org; Tue, 10 Mar 2026 04:52:56 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vzspi-0005qI-J7 for qemu-devel@nongnu.org; Tue, 10 Mar 2026 04:52:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1773132771; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=u57xTiOfwrmS3jdy8nQn0xyMwms1xDAVYGyJkK4uNho=; b=fM9MYaAeDeVH01/JJrsTTSz28d7g5XSULD/Qt4FrMOCA0Q72U6cVcqqwpjKu1pDysTBzCI BpiHwzjYD6cGZlBht2jktKnue83c1Tph55kyiWLCreT448uUPQjF0CHW8f4YbWmYOBw/Lf giqwyE7fFFrgfAsqnCDTx3Hs5dOUEmc= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-543-MFD3CyXJOCqdxkKonB06XA-1; Tue, 10 Mar 2026 04:52:50 -0400 X-MC-Unique: MFD3CyXJOCqdxkKonB06XA-1 X-Mimecast-MFC-AGG-ID: MFD3CyXJOCqdxkKonB06XA_1773132769 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4104D1955F38; Tue, 10 Mar 2026 08:52:49 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.12]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CF6F01956095; Tue, 10 Mar 2026 08:52:48 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 4BE3121E6614; Tue, 10 Mar 2026 09:52:46 +0100 (CET) From: Markus Armbruster To: Tejus GK Cc: qemu-devel@nongnu.org, Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Peter Xu , Fabiano Rosas , Eric Blake Subject: Re: [PATCH v2 1/1] io: make zerocopy fallback accounting more accurate In-Reply-To: <20260309090907.956330-1-tejus.gk@nutanix.com> (Tejus GK's message of "Mon, 9 Mar 2026 09:09:01 +0000") References: <20260309090907.956330-1-tejus.gk@nutanix.com> Date: Tue, 10 Mar 2026 09:52:46 +0100 Message-ID: <87h5qom5gh.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -3 X-Spam_score: -0.4 X-Spam_bar: / X-Spam_report: (-0.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.819, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.903, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Tejus GK writes: > Currently, the dirty-sync-missed-zero-copy stat is incremented only when > an entire batch of IO operations fails to use zerocopy and falls back to > a normal copy. As long as at least one IO in the batch is successfully > zero-copied, the whole batch is treated as a success. This hides > individual IO fallbacks and makes the migration stat less accurate than > it could be. > > Make the stat more accurate by reporting at a finer granularity, i.e, by > incrementing for every individual IO fallback that occurs. > > Suggested-by: Peter Xu > Signed-off-by: Tejus GK [...] > diff --git a/qapi/migration.json b/qapi/migration.json > index f925e5541b..94977b8810 100644 > --- a/qapi/migration.json > +++ b/qapi/migration.json > @@ -58,8 +58,7 @@ > # (since 7.0). > # > # @dirty-sync-missed-zero-copy: Number of times dirty RAM > -# synchronization could not avoid copying dirty pages. This is > -# between 0 and @dirty-sync-count * @multifd-channels. > +# synchronization could not avoid copying dirty pages. > # (since 7.1) > # > # Since: 0.14 Dropping the documented upper limit might make the value harder to interpret. Thus my question: how is this value to be used?