From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) (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 9524E22A7E8 for ; Mon, 7 Apr 2025 13:27:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744032461; cv=none; b=AeLTaPEW/SClXo5wkqiwyiNBoty+sHwfsc6nNyv95YDtv5bdfKzPqxYPD16aoSJYk27aFlPEqdzirkboV2xXd6oGYAAnt5CT9c0ib6sTT4YBmLeoufyhsfNSyp+bthXCXdRRuKGDCoQXINeGvk+ROcagBzp6+F4M93zoJUHUyng= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744032461; c=relaxed/simple; bh=HCsXn91wSxtJmwJS7kx+ePBW9Yt9vtglMV0WAxHHo20=; h=Mime-Version:Content-Type:Date:Message-Id:Subject:From:Cc:To; b=u3/6qGLiF91RojHdbx6FsW3d7tgx2MUUTOcGcBALdy2n+Cxr7Ez/58e+TigleotOZ1hCaWmc8KDZLhBWAhteeUl7Je8VdX4VxO2TdKMDzsJsLxIsuR8i9H77M7i50EOESnSIGivJ5HEx/K1e8cx+Ha1/VeuD4IVZJkEKdklz0tU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=cknow.org; spf=pass smtp.mailfrom=cknow.org; dkim=pass (2048-bit key) header.d=cknow.org header.i=@cknow.org header.b=lNtNSDMe; arc=none smtp.client-ip=95.215.58.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=cknow.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=cknow.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=cknow.org header.i=@cknow.org header.b="lNtNSDMe" Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cknow.org; s=key1; t=1744032455; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=j/Kd4gmTIBsFbGqlUqqNMDa2TriLSz39d1NLHeVDZhk=; b=lNtNSDMelpXj5j7iXy9yuM+SO9iNIgdwvYoy1EUevFrw4oFHfLs9Yv97Gl1ilwj5O+KkBv 0UBm7enjX/2p3fK4jSnAXwmxXbb4bjnyroWOkSjiqJ24mr0Zz6+9pNSS4c4nlCRtymslmI oAFWHrFK49NIznzOU3x1qE9uBzMHaMgv3luI5TDssIoBAcAK4hYugP9H73FiZjzb2Jh51B i2d+DNKEmVpMy7CcQWiLj5PS2062+2SwF+1VmrKFjlHFPPNYfUezKunTHgwYK/9eIrinO7 chO42nA4gxMd8ItCe72BMcG5fRnSW2YnXophtWzmQB3fjYmim5OxoKQIBYTZAg== Content-Type: multipart/signed; boundary=bb50bd7793a9c5dec92a4e569833fe2102942b111b5b1897cd30a926116a; micalg=pgp-sha256; protocol="application/pgp-signature" Date: Mon, 07 Apr 2025 15:27:21 +0200 Message-Id: Subject: Is kernel/Kconfig.hz still up-to-date? X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: "Diederik de Haas" Cc: , "Bagas Sanjaya" , "Dang Huynh" To: "Greg Kroah-Hartman" , "Christoph Lameter" , "Andrew Morton" , "Thomas Gleixner" X-Migadu-Flow: FLOW_OUT --bb50bd7793a9c5dec92a4e569833fe2102942b111b5b1897cd30a926116a Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Hi, I recently had a discussion about the use of HZ_1000 in the kernel configuration and the impact on performance. My reading of the HZ_1000 help text tells me that HZ_1000 is primarily useful for DAW and other systems where RT capabilities are (most) important. This is due to "systems requiring fast interactive responses to events", whereby I put the emphasis on *requiring*. As *I* understand the rest of the help texts, a higher Hz value can/will have a negative effect on f.e. IO performance. And I'm not entirely sure, but it seems each CPU (core?) multiplies the nr of interrupts? But, doing a ``git blame`` on the choices shows that apart from a spelling fix in 2025, all the text hasn't changed since 2005/2006. But a LOT has changed since then. There are more architectures and the hardware and the kernel itself have changed quite a bit since then. While the Kconfig.hz default is still HZ_250, the x86 defconfig changed to HZ_1000 in 5cb04df8d3f0 ("x86: defconfig updates") (in 2008) and there are various distros which have switched to HZ_1000. So my questions are: are the Kconfig help text still accurate for current (hardware) systems and kernels? Is HZ_250 still the most sensible default? Or is the 'newer' HZ_300 better? Or even HZ_1000? And does that apply only for x86 or for all architectures? (distros seem to vary between architectures f.e.) Cheers, Diederik --bb50bd7793a9c5dec92a4e569833fe2102942b111b5b1897cd30a926116a Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQT1sUPBYsyGmi4usy/XblvOeH7bbgUCZ/PSwAAKCRDXblvOeH7b brCXAQCjkQNOEDFeRZ7o+GMldSO4I5E7sDhni1jp4aP7+H+xrwEAiIBbyJRqmnsd TC0DnBSS5fnOfyVwXl7f7OQR08U32Aw= =9VNX -----END PGP SIGNATURE----- --bb50bd7793a9c5dec92a4e569833fe2102942b111b5b1897cd30a926116a--