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 A7840CCF9E3 for ; Tue, 4 Nov 2025 17:56:10 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vGLFy-0001i7-DW; Tue, 04 Nov 2025 12:55:47 -0500 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 1vGLEq-0000re-KK for qemu-devel@nongnu.org; Tue, 04 Nov 2025 12:54:38 -0500 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 1vGLEo-0006j9-Uh for qemu-devel@nongnu.org; Tue, 04 Nov 2025 12:54:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762278874; 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=AFueM27NLiZq+PeHyP0oGI+SClKRjJY3eSQT1wbYQdE=; b=XanMJd6i4blhlfWKI1ryh0Azb0KYTex62RJg2Vq++goO/6fc3U4WqL3Kc9alj5N+IOhEqW oj2ABjnb4RqzwRkv8x8GA8uTmIFLkHrAIFQBG+Nt1dXC7D/5gkbKp83S8UJyNLMK2KLc/l KBTfhDFqoDu3k/503SccAHXzXsRq2NI= 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-126-knYBxHU-OjWJCG9rSq2O7A-1; Tue, 04 Nov 2025 12:54:32 -0500 X-MC-Unique: knYBxHU-OjWJCG9rSq2O7A-1 X-Mimecast-MFC-AGG-ID: knYBxHU-OjWJCG9rSq2O7A_1762278872 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 EDD5119560B7; Tue, 4 Nov 2025 17:54:31 +0000 (UTC) Received: from merkur.fritz.box (unknown [10.45.226.47]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id AB4DA1800451; Tue, 4 Nov 2025 17:54:30 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [PULL 04/27] aio-posix: keep polling enabled with fdmon-io_uring.c Date: Tue, 4 Nov 2025 18:53:52 +0100 Message-ID: <20251104175415.525388-5-kwolf@redhat.com> In-Reply-To: <20251104175415.525388-1-kwolf@redhat.com> References: <20251104175415.525388-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.788, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Stefan Hajnoczi 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 Reviewed-by: Kevin Wolf Message-ID: <20251104022933.618123-5-stefanha@redhat.com> Signed-off-by: Kevin Wolf --- 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; } -- 2.51.1