From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 91A741CD202 for ; Thu, 21 Nov 2024 11:31:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732188676; cv=none; b=dEdCiOcqkd01P3UhBsNc5g4yLicG9lx/o9RliObV8pDwGqA11ZpwMAthmDIK2TbQ/8HjdoMWpzRxqL9sfyEyubBSZpC9uj812DYB+YpHWykf8kCmreJwMx1tZ7cnohaKN5PsCXGn6rbgCaJ5Z73tsv/QGpsTUHU8fZ+ge7xQB9U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732188676; c=relaxed/simple; bh=zs8SKII8mMGsvDX3KPlUXSYfC/V4zfVu2hLTYizAESU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WAAEG6vPylplmGg3tXZ+DKgjZWm2xt46yDGddGgjqpXd4mmJS15RRHyleFz/cyXV0kC4efLrcjvgI2CPHU4y7osab5R5aaR5jaQ6jFqJu7inRB10JtfOFkUSOEDiR/tKUyHz9I16nhiQhs9mdaqec22S+DLQxBYSQzxDLP2c7Xg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=erTKTJ3X; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="erTKTJ3X" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=zs8SKII8mMGsvDX3KPlUXSYfC/V4zfVu2hLTYizAESU=; b=erTKTJ3X8pOVhoVnm7oEg1NYZP iFs6UeE4HTZwmvLXmHYMlpt4+OdF3YcweoO1OTiiv4jiy2h9WPsmK+LYVTRxVboHASzhuzI9wLgwt 3vyoEP9upiSmvO90hdC3Yt8lZJ04ONgq+yuVNjUAJgvAQ5iVau1r5vxSPePnuBPDbzQvVckHKNEh6 XowukGWxVvzQkVihGk2zzgPDT5MKSKSyNGQqjn/BWbHAqxikY6W8KD4IzXZL2n4QsWvVuLfbpZbm7 6CAl1DtD/j5DguafdmuNlFdS9hvvIoK9ho/ZUNYXBHnXAF+WXi8+hHYY7fTJirm9aRTWdlBKfkW7s ggER41eA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tE5Or-00000000Zk1-19nH; Thu, 21 Nov 2024 11:31:05 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id E10C430068B; Thu, 21 Nov 2024 12:31:04 +0100 (CET) Date: Thu, 21 Nov 2024 12:31:04 +0100 From: Peter Zijlstra To: Vadim Fedorenko Cc: Borislav Petkov , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Thomas Gleixner , Yonghong Song , Vadim Fedorenko , Mykola Lysenko , x86@kernel.org, bpf@vger.kernel.org, Martin KaFai Lau Subject: Re: [PATCH bpf-next v8 2/4] bpf: add bpf_cpu_time_counter_to_ns helper Message-ID: <20241121113104.GF24774@noisy.programming.kicks-ass.net> References: <20241121000814.3821326-1-vadfed@meta.com> <20241121000814.3821326-3-vadfed@meta.com> Precedence: bulk X-Mailing-List: bpf@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: <20241121000814.3821326-3-vadfed@meta.com> On Wed, Nov 20, 2024 at 04:08:12PM -0800, Vadim Fedorenko wrote: > The new helper should be used to convert cycles received by > bpf_get_cpu_cycle() into nanoseconds. This is pertinently false, as written here you're looking for a single reading into a clock value, while that is exactly not what you want. Please, go write real changelogs