From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9DB9934D934 for ; Tue, 10 Mar 2026 14:12:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773151925; cv=none; b=CECfbXUHyUgptyeNmohNUMTlbEFM7+lHyxGJ79dyN9b/CeAbtfZhq7fVgd1iYo/8oxnoSkYQadAAPSVSbNW8/sGPi+vgX3nIO9sps9tuO5VO1zD4OxahB3CMSH5ohvYpQtF0XlO1Wxlf78UgzihW340cUKNcD2eQ4SqSKHN/gkc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773151925; c=relaxed/simple; bh=+TcL+IUx6zJmNcAGvV4DgqcF31CbjxR50XVoyThwmtI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=bCgTOwl7uLcBtYfOAM3GEAGVKE9qN9hG003Amem9wpd9OlWCI5Ku6AHrOlplxt/KBcjqGWGawhOzlC/VvbItoUhUbO7a/C191Bana38b0MXEWwTrT333ULvEMSbwddWAgC75IcczzMwjhyIQXEfZ2NCMYzL09V+++/2kzRRLMzQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=kNlgJ4zd; arc=none smtp.client-ip=209.85.210.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="kNlgJ4zd" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-8297d2c1e64so2076587b3a.2 for ; Tue, 10 Mar 2026 07:12:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1773151924; x=1773756724; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=4S848XCbrnwNHShj4M1DfLZem9m3I2fkthB5jWjWU0s=; b=kNlgJ4zdsVd3qBHAum9nGNmghoaPQJ377cqW0FhYwSQfu8Y3Di9c4AcY6IQ2DzKuRJ oVi736ic09nXzUOlRsixjGdXO5fdx0elouVfO8l0ZsJiHNT83rHWTG/LltWBWz0WDHhy x6fy3Zn1cGT265aKkmNNpOCvjEevsJ9faDOBO4arLfguU1f/HYVcHO9R+9BK99ypPVN6 3kcfBAXeslABcergSuuCXkOVJkN6FGvj4QDFl5FDZGAt84pHBOIxpRgr1AsOzShYGpsX zLaiV2m3wHEbOIYXSSlHFjQZQcAeucS46eYbGPFtgBNEqm/nciqeSXecqHqpLY4rMADC M6YA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1773151924; x=1773756724; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=4S848XCbrnwNHShj4M1DfLZem9m3I2fkthB5jWjWU0s=; b=VQCCkffKq819/dplB2cPew9x717lWIZO6H183iUiYh9hSDCpMtI3QklI6Y6/nE2dpE g/qGa3FMOKiphGKmqOEjWQ1UzInYXYOaU8vtLqneVnP4LA9HV4nmpJGzqhz8/NFLPoPf icDgXvvoQVn9prxpoFTMkNDyzXckz4jdXOXiw6cfbhsuIrJ04XKuZjJlypddC0QgLngS TRwuQ3xf0eFKaaGpV7gvFQ/8rBxcp9187o49hJx77Nvs3e01A29GUfJdgfRiOiHhvE/E fd2gb/l8irVwPHy1zfehWejVbZH1qXznKHZJaPMgsdZHZAg7rr2zVGxCwJ9q3AHEL0n9 wqzQ== X-Forwarded-Encrypted: i=1; AJvYcCUC/31CafYAuOAfcVaqcHxIcQl/KEv5ZivE0dzGUTfe0IJ/3JykK4u/GKFGbjpXZDmB2MLpQ37Z2OKl7Lg=@vger.kernel.org X-Gm-Message-State: AOJu0Yy/KyAtODQ8SbZl9tWuhHYEzgXAnWK1aXogxn/GMVYXkRswFwEQ 2FaWcoKoBYutEdgxlo0lQc1uqB4iqAzuxV/Wrw+F5NgLSl5JEwwX+SbOJGaO2R7p8z8gKTNYLpR jywQ8Ew== X-Received: from pfbei4.prod.google.com ([2002:a05:6a00:80c4:b0:7b9:1e6:e516]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:3021:b0:824:ab8d:6f9e with SMTP id d2e1a72fcca58-829a2e13ba0mr13263019b3a.29.1773151923806; Tue, 10 Mar 2026 07:12:03 -0700 (PDT) Date: Tue, 10 Mar 2026 07:12:02 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260309092132.2484-1-lirongqing@baidu.com> Message-ID: Subject: Re: =?utf-8?B?562U5aSNOiBbPz8/P10gUmU6IFtQ?= =?utf-8?Q?ATCH=5D_KVM=3A_eventfd=3A_Remov?= =?utf-8?Q?e?= redundant synchronize_srcu_expedited from irqfd assignment From: Sean Christopherson To: "Li,Rongqing(ACG CCN)" Cc: "pbonzini@redhat.com" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="us-ascii" On Tue, Mar 10, 2026, Li,Rongqing(ACG CCN) wrote: > > > Removing this call reduces latency during resampling irqfd setup. > > > > May I ask why you're micro-optimizing VMst with an in-kernel I/O APIC? > > Few devices use it anymore; I just think the kernel ABI shouldn't require > synchronize_srcu_expedited. That's a *very* broad stance to take. For all intents and purposes, eliminating SRCU synchronization in KVM means eliminating SRCU usage entirely. That's not completely infeasible, but I don't see it happening anytime soon given how much KVM relies on the properties of SRCU to avoid unnecessary serialization.