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 5FAB82E973C; Fri, 27 Jun 2025 16:51:00 +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=1751043060; cv=none; b=P7PEoPyG0J2wAfGwNBViWD1I9Ke40rXrHRgoT86rOB/XpIZTAUewr28i/zWQV1V39DCI4pTztf5eQfDP5CWzsHREsmlPVJpvOLmGvv9EPxjn7LNPRsBQ+IN9OOAqaQqA22iK2AYrN6euP0MOMyvxzWtVdM4IaFi/D+UNd0m2tDA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751043060; c=relaxed/simple; bh=aJ07hUJYwbrLew9sRNGrGzo4e2otJNCPPs8hRpvB6NM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LRWUdK+g1HYlLOjUWYeFeuxXUjm7TlvBg6cQYFrJ9Tl4U28SHd+XCznXMP7xrniqWNMsHWCDxOQDHjGWXjO6xAqim/F1WN4cU2qRUsEw/+V2yD1W5WXWBgoZD7o0vCodB4mt3+Ds9Mu821dFKkq3pa23qcGpeUZ2Ij88spJXZcM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=f9K7gUdn; 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="f9K7gUdn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80D0EC4CEEF; Fri, 27 Jun 2025 16:50:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751043059; bh=aJ07hUJYwbrLew9sRNGrGzo4e2otJNCPPs8hRpvB6NM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=f9K7gUdnIqiY5zPsSl1E7pUaIlL4K90dW6IcNc+cEcGIQes8wPgu30tHrJbYTenpN mjvNA/KAJkVHtilaLD5WIoMfmLutwndUyjFw0yZ6EqywoDw575H20G/fS+PwfIg1AE poxcGCDVmfHdsdBIWr82zj/Mw3iBqhPNPc2w34f7JOpe0GS8pXGeV9Qa/0letnq0R5 ppck3qdjm1JTx+gEaW4WKnA0jAP7hRQB2XcW4zF+STN4MIWaAp9RzElbkUbA3yu9hg 105vddSxk/C5MqPnyiyAY4/2JWXxdxCkuK2356AWbxIJ55LGb2UnOf7y1ROKLSPOYI pwM6rzB8H/APw== Date: Fri, 27 Jun 2025 06:50:58 -1000 From: "tj@kernel.org" To: "Wlodarczyk, Bertrand" Cc: Shakeel Butt , "hannes@cmpxchg.org" , "mkoutny@suse.com" , "cgroups@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "inwardvessel@gmail.com" Subject: Re: [PATCH v2] cgroup/rstat: change cgroup_base_stat to atomic Message-ID: References: <20250624144558.2291253-1-bertrand.wlodarczyk@intel.com> Precedence: bulk X-Mailing-List: cgroups@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: Hello, On Fri, Jun 27, 2025 at 01:15:31PM +0000, Wlodarczyk, Bertrand wrote: ... > > Also the response to the tearing issue explained by JP is not satisfying. > > In other words, the claim is: "it's better to stall other cpus in spinlock plus disable IRQ every time in order to > serve outdated snapshot instead of providing user to the freshest statistics much, much faster". > In term of statistics, freshest data served fast to the user is, in my opinion, better behavior. This is a false choice, I think. e.g. We can easily use seqlock to remove strict synchronization only from user side, right? > I wouldn't be addressing this issue if there were no customers affected by rstat latency in multi-container > multi-cpu scenarios. Out of curiosity, can you explain the case that you observed in more detail? What were the customer doing? Thanks. -- tejun