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 48837C7115B for ; Fri, 20 Jun 2025 00:14:40 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uSPLQ-0000dc-0p; Thu, 19 Jun 2025 20:11:00 -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 1uSPLM-0000cX-EL for qemu-devel@nongnu.org; Thu, 19 Jun 2025 20:10:56 -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 1uSPLK-0004qK-Rv for qemu-devel@nongnu.org; Thu, 19 Jun 2025 20:10:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1750378254; 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=ABjFHVE9PdYgMVctSBMt9rQQIoyVefcMDqx5SE750d4=; b=E0iAdvzyCH2742Ukq/Y1Tp3lG1VWIrnGj/nrTWzdcXGRlMP03WBdUJdilRV0OdZVbSOHql HKBohGaL5XmqCCw/d5AZjCrUhnRG5oezAsBTdVLFpzJHvDDuxhDOQN71Hdd793jL8ln3DS q/aADevq3HBurZuHlKR4X3y4YSbRqo4= Received: from mx-prod-mc-05.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-502-Y9f75zWxM-mG3sDYUzfSVQ-1; Thu, 19 Jun 2025 20:10:50 -0400 X-MC-Unique: Y9f75zWxM-mG3sDYUzfSVQ-1 X-Mimecast-MFC-AGG-ID: Y9f75zWxM-mG3sDYUzfSVQ_1750378249 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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D31D119560A2; Fri, 20 Jun 2025 00:10:48 +0000 (UTC) Received: from localhost (unknown [10.2.16.120]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1E53018003FC; Fri, 20 Jun 2025 00:10:47 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Hanna Reitz , Kevin Wolf , Stefan Weil , Paolo Bonzini , Fam Zheng , eblake@redhat.com, Stefano Garzarella , qemu-block@nongnu.org, Stefan Hajnoczi , Aarushi Mehta , hibriansong@gmail.com, Chao Gao Subject: [PATCH v2 02/12] aio-posix: keep polling enabled with fdmon-io_uring.c Date: Thu, 19 Jun 2025 20:08:18 -0400 Message-ID: <20250620000829.1426291-3-stefanha@redhat.com> In-Reply-To: <20250620000829.1426291-1-stefanha@redhat.com> References: <20250620000829.1426291-1-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: -39 X-Spam_score: -4.0 X-Spam_bar: ---- X-Spam_report: (-4.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.897, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=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; } -- 2.49.0