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 2FDDCCA0FED for ; Wed, 10 Sep 2025 18:11:01 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uwPE4-0004vi-MB; Wed, 10 Sep 2025 14:07:28 -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 1uwPDe-0004L6-Sj for qemu-devel@nongnu.org; Wed, 10 Sep 2025 14:06:58 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uwPDT-00053a-JJ for qemu-devel@nongnu.org; Wed, 10 Sep 2025 14:06:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757527606; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MGnG+XdtmTxntikOC8JogL74daSKQSHrsTNR1uFQlNA=; b=WwhlKraC4SW/cRvYdpnAGG5/jjxtFPgSQDT6VbkZzkL4SgxHbhR9YVhi2qdppYGlqjdFAv 6n1hRoMQvt1f84PMBmnZS7fCeLNyhy8CX30hjIuk2Q7/eICdAFOJcRKs0k6y3MSg4EtR3G EttXXJkMOer5GV6Vcpg3Ofetbh83cbg= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-138-yc7g6dkZMZyexE5Im2m2Pw-1; Wed, 10 Sep 2025 14:06:42 -0400 X-MC-Unique: yc7g6dkZMZyexE5Im2m2Pw-1 X-Mimecast-MFC-AGG-ID: yc7g6dkZMZyexE5Im2m2Pw_1757527601 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7F9C91800296; Wed, 10 Sep 2025 18:06:41 +0000 (UTC) Received: from localhost (unknown [10.2.17.66]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id E85E21800446; Wed, 10 Sep 2025 18:06:40 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Aarushi Mehta , Fam Zheng , Stefano Garzarella , Hanna Czenczek , eblake@redhat.com, Stefan Hajnoczi , Kevin Wolf , qemu-block@nongnu.org, hibriansong@gmail.com, Stefan Weil , Paolo Bonzini , Chao Gao Subject: [PATCH v4 02/12] aio-posix: keep polling enabled with fdmon-io_uring.c Date: Wed, 10 Sep 2025 13:56:53 -0400 Message-ID: <20250910175703.374499-3-stefanha@redhat.com> In-Reply-To: <20250910175703.374499-1-stefanha@redhat.com> References: <20250910175703.374499-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Commit 816a430c517e ("util/aio: Defer disabling poll mode as long as possible") kept polling enabled when the event loop timeout is 0. Since there is no timeout the event loop will continue immediately and the overhead of disabling and re-enabling polling can be avoided. fdmon-io_uring.c is unable to take advantage of this optimization because its ->need_wait() function returns true whenever there are new io_uring SQEs to submit: if (timeout || ctx->fdmon_ops->need_wait(ctx)) { ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Polling will be disabled even when timeout == 0. Extend the optimization to handle the case when need_wait() returns true and timeout == 0. Cc: Chao Gao Signed-off-by: Stefan Hajnoczi Reviewed-by: Eric Blake --- util/aio-posix.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/util/aio-posix.c b/util/aio-posix.c index 2e0a5dadc4..824fdc34cc 100644 --- a/util/aio-posix.c +++ b/util/aio-posix.c @@ -559,7 +559,14 @@ static bool run_poll_handlers(AioContext *ctx, AioHandlerList *ready_list, elapsed_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - start_time; max_ns = qemu_soonest_timeout(*timeout, max_ns); assert(!(max_ns && progress)); - } while (elapsed_time < max_ns && !ctx->fdmon_ops->need_wait(ctx)); + + if (ctx->fdmon_ops->need_wait(ctx)) { + if (fdmon_supports_polling(ctx)) { + *timeout = 0; /* stay in polling mode */ + } + break; + } + } while (elapsed_time < max_ns); if (remove_idle_poll_handlers(ctx, ready_list, start_time + elapsed_time)) { @@ -722,7 +729,7 @@ bool aio_poll(AioContext *ctx, bool blocking) * up IO threads when some work becomes pending. It is essential to * avoid hangs or unnecessary latency. */ - if (poll_set_started(ctx, &ready_list, false)) { + if (timeout && poll_set_started(ctx, &ready_list, false)) { timeout = 0; progress = true; } -- 2.51.0