From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 04D3A2505CF; Mon, 24 Mar 2025 07:16:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742800582; cv=none; b=FSiKagDJsxsx/25SWU/yMUwQ43a9E7tIinBJP0QlgsNxOlQmlNGS3JgGqf5hHUvxD5CrY0MrOb7Cz5i4DM1q2qo1G8r2l7uwJNRR13FmPhOFsyS/LXphTU+5AV280Cd3D+TJXxaR75CJCpqkg6SsORIzIIt8kPz4QjtWtmlHlYs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742800582; c=relaxed/simple; bh=JSUdGazAmz6LBM0jLnWsCHf3QHtK7b1YmV5op+kF/eM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=sTQSe6d05qxUNkfhpqsk9lPAbcEQD29IaiEaTchiy4IKCHAUuvoid4XRcLyImyUtLzR89pXydGBoG5Z7uEJ2IxeeGoS/NWcKWL6RHtgI7+UWGtLSyJjSibWPDkvgi0fBZhQgcCf3pJlorIHyODU62NIDWZY4V5mrSgh0z5zoWaE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qBj5LZfx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qBj5LZfx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8BF39C4CEE4; Mon, 24 Mar 2025 07:16:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742800581; bh=JSUdGazAmz6LBM0jLnWsCHf3QHtK7b1YmV5op+kF/eM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qBj5LZfxve5cmrhWDISfxEo6blCjzsrMdBrjY0CKRQz4ssHHtAjp/Kx5I10Mj+l6x cMhw1SRAJUKOVfP9+9PFxVLxyy7Fkr96mejZoYU4N+h6CndON3jVfQ0cckS+dzZclj BNjCcZNJSjmCC+lRH1Dw7Psvp3zlx844TcKewPbnuee5v/BO/PHeVl3IS5pc3jMEzw dUZ22wBAeX0da+VKwwmdSOiuLV9/44HK78astaCWEa5YK/2oRgE6/8rWCSWJsmwfei HDv4oau33VLhzz/Zqam98rl7UlElbKLySvghgc2ZxYOfgF/ClRcyLJm/jbb/MZAXVq yoVNSE3/0plWA== Date: Mon, 24 Mar 2025 08:16:14 +0100 From: Ingo Molnar To: Eric Dumazet Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Peter Zijlstra , Steven Rostedt , linux-kernel , Alexei Starovoitov , Daniel Borkmann , Masami Hiramatsu , x86@kernel.org, bpf@vger.kernel.org, Eric Dumazet , Greg Thelen , Stephane Eranian Subject: Re: [PATCH] x86/alternatives: remove false sharing in poke_int3_handler() Message-ID: References: <20250323072511.2353342-1-edumazet@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: * Eric Dumazet wrote: > > What's the adversarial workload here? Spamming bpf_stats_enabled on all > > CPUs in parallel? Or mixing it with some other text_poke_bp_batch() > > user if bpf_stats_enabled serializes access? ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > Does anything undesirable happen in that case? > > The case of multiple threads trying to flip bpf_stats_enabled is > handled by bpf_stats_enabled_mutex. So my suggested workload wasn't adversarial enough due to bpf_stats_enabled_mutex: how about some other workload that doesn't serialize access to text_poke_bp_batch()? Thanks, Ingo